Introduction

Plant edible oils are a major source of lipids in our diet, providing essential fatty acids, energy, and fat-soluble vitamins necessary for daily life1. Vegetable oils are frequently utilized for cooking, frying, baking, salads, and a variety of other industrial applications2. With the increasing global population, the demand for oil worldwide continues to be robust. Reports indicate an increasing trend in global consumption of vegetable oils to 212.9 million metric tons, as global production has reached 222.8 million tons in 2022–233. The palm and palm kernel oil accounted for 37% of worldwide vegetable oil consumption3. Palm oil (Elaeis guineensis), sunflower (Helianthus annuus), groundnut (Arachis hypogaea), and black mustard (Brassica nigra) oils are among the most consumed vegetable oils in India. Besides these conventional oils, minor oils such as coconut (Cocos nucifera), almond (Prunus dulcis), safflower (Carthamus tinctorius), sesame (Sesamum indicum), and Niger (Guizotia abyssinica) are also becoming increasingly popular. At present, the production of oil crops in India is inadequate to fulfill the country’s demand. Consequently, the import of edible oils in India rose to 56% (NMEO-OP, 2024).

The growing consumer awareness regarding their health has led to more interest in safer processed food. Eco-friendly extraction techniques such as cold pressing (CPE), ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), subcritical water extraction (SWE), and supercritical fluid extraction (SFE) have gained significant interest for their environmental sustainability and energy-saving advantages4. Among these, cold pressed oils are increasingly being popularized among consumers due to their health-beneficial effects. These oils are often considered functional foods as these oils are rich sources of essential fatty acids as well as other minor components such as tocopherols, carotenoids, and polyphenols that are associated with health benefits (Kostadinovic & Mitrev, 2013). Furthermore, cold pressed oils are advantageous over refined oils largely due to their high oxidative stability resulting from large recovery of bioactive substances which have been proven to retard lipid oxidation, not being otherwise removed during refining processes5. These oils help lower atherosclerosis, artery disease, and stroke, due to the presence of vitamin E at high levels (Adeleke & Babalola et al., 2020). The inclusion of cold pressed oils in the diet can be beneficial as they help meet the adequate recommended daily intake of antioxidants (vitamin E), especially in countries like the United States, where 90% of the population falls short of adequate vitamin E intake6. According to the Global Burden of Disease study 2019, a global age-standardized prevalence of vitamin A deficiency was estimated to be 7%, accounting for 23.1 million cases7. Fortifying vegetable oils with vitamin A can help combat deficiency in at risk populations, offering improved stability and absorption8.

The quality and stability are important characteristic features of edible oils, which directly affect consumer acceptance and market value9. However, each cold pressed oil has a characteristic fatty acid composition and other minor accompanying compounds, which significantly affect quality and stability10. Furthermore, it is difficult to obtain quality cold pressed oils consistently as it is largely affected by several factors such as raw material, growing conditions, harvesting time, environmental conditions, storage conditions, seed treatment before extraction, extraction methods, and also processing conditions11. These oils are more resistant to lipid oxidation, despite having a higher starting oxidation level, as they are produced by pressing seeds only, thus retaining their lipid oxidation byproducts12.

The availability of cold-pressed oils in the Indian market has expanded significantly, with these oils increasingly recognized for their health-promoting properties. Ensuring that cold-pressed oils meet the highest standards of quality, stability, and nutritional value is essential to maximize their potential health benefits. Furthermore, enhancing the oxidative stability of these oils through the incorporation of natural bioactive molecules could minimize the formation of harmful oxidized lipids, thereby improving product safety and quality. A critical review of the existing literature reveals that certain functional properties of minor edible oils, such as their anti-inflammatory effects, remain insufficiently investigated or, in some cases, entirely unexplored. Additionally, the majority of prior studies have focused on oils extracted using solvent-based methods under laboratory conditions, whereas the compositional and functional attributes of commercially available cold-pressed oils remain largely underreported based on procedures performed in the laboratory. This is particularly concerning given the rising consumer demand for unrefined oils and the need to ensure product quality and authenticity. Furthermore, limited research has addressed the relationships between bioactive compounds (e.g., carotenoids, phenolics, and flavonoids), oxidative stability, nutritional profiles, and associated health benefits of cold-pressed oils, particularly in the Indian context. This study aims to bridge these gaps by conducting a comprehensive characterization of commercially available cold-pressed oils derived from seeds, nuts, and mesocarp in the Indian market. By providing robust and reliable data on the compositional and functional properties of these oils, this research seeks to offer valuable insights for both consumers and the scientific community, thereby supporting the development and promotion of high-quality, nutritionally beneficial oil products.

Materials and methods

Materials

Supelco 37 Component FAME Mix, Bradford reagent, bovine serum albumin (BSA, molecular weight: 67,000 Da), DPPH (≥ 90%), BF₃·MeOH (14% wt./v), Folin-Ciocalteu reagent, DMSO (≥ 99.7%), gallic acid (≥ 98.0%), and catechin (≥ 99.0%) were procured from Sigma-Aldrich Chemical Co. (St. Louis, MO, USA) and used without further modification. The reagents including KH₂PO₄, KI, Na₂S₂O₃, Na₂SO₄, AlCl₃, HNO₃, H₂SO₄, and HClO₄ were obtained from Thermo Fisher Scientific India Pvt. Ltd. (Powai, Mumbai, India). All other chemicals used in the study were of analytical grade and used as received. Double-distilled water prepared using a quartz cabinet distillation unit (QCD250, Labquest Borosil, Pune, India) was used throughout the experiments.

Samples collection and preparation

Commercially available cold pressed, unrefined vegetable oils obtained from nuts and fruits were purchased from the local market in Eluru District, Andhra Pradesh located at 16°42′40"N latitude and 81°5′41"E longitude. These oils included almond (AlO), sunflower (SuO), safflower (SaO), sesame (SeO), mustard (MuO), niger (NiO), coconut (CoO), and groundnut (GnO). Cold pressed palm oil (PaO) was acquired from the ICAR-Indian Institute of Oil Palm Research, located at 16.8122° N latitude and 81.1319° E longitude in Pedavegi, Eluru, Andhra Pradesh, India. As indicated, oils were extracted through an unconventional mechanical cold processing method without the use of solvents or heat treatment. The oils were collected and stored in the dark until further analysis.

Determination of fatty acid profiling

To analyze the fatty acid profile, the test sample was trans-esterified with methanolic NaOH (0.5 N) in the presence of BF3 (14% wt./v) for 30 min at 85 °C. Once n-hexane was added, it was mixed thoroughly and allowed to stand until the phases separated. The upper organic phase was transferred to a new vial and dehydrated using Na2SO4. The nitrogen was used to concentrate samples for 15 s to obtain fatty acid methyl esters (FAMEs). The FAMEs were separated using PerkinElmer, Clarus 690 gas chromatography (Massachusetts, USA) equipped with a flame ionization detector. The COL-Elite563 fused silica column (PerkinElmer, Massachusetts, USA, 100 m long × 250 µm diameter × 0.2 µm thick) was employed for peak separation. In split mode, 0.1 µl of the sample was injected (1:50 split ratio). The initial oven temperature was set to 100 °C for 4 min, then raised to 240 °C at the rate of 5 °C/min, and held for 25 min. The temperatures of the inlet and detector were set to 220 °C and 240 °C, respectively. Nitrogen was used as a carrier gas, with a constant flow rate of 1 mL/min13. Supelco 37 Component FAME Mix from Sigma-Aldrich Chemical CO. (St. Louis, MO., USA) was used as a standard for fatty acid identification. The peak area percentage was calculated using the TotalChromNav (TCNav) software.

Determination of nutritional quality indices (NQI)

The nutritional quality indices, such as the atherogenicity index (AI) and thrombogenicity index (TI) of cold pressed oil, were evaluated using the method described by Ulbricht and Southgate14. The following formula was used to calculate AI and TI (1 and 2). The cholesterolemic effect of cold pressed oils was calculated using formula (3) provided by Santos et al. (2002) and expressed as a ratio of hypocholesterolemia to hypercholesterolemic fatty acid (HH).

$$\text{AI}=\frac{{C}_{12:0}+4\times {C}_{14:0}+ {C}_{16:0}}{\sum MUFA+\sum \left(\omega 6\right)+ \sum \left(\omega 3\right)}$$
(1)
$$\text{TI}=\frac{{C}_{14:0}+{C}_{16:0}+ {C}_{18:0}}{0.5 \times \sum MUFA+0.5 \times \sum \left(\omega 6\right)+ \sum \left(\omega 3\right)}$$
(2)
$$HH=\frac{{C}_{18:1}+{C}_{18:2}+ {C}_{18:3}+ {C}_{18:4}+ {C}_{20:4}}{{C}_{14:0}+{C}_{16:0}}$$
(3)

Determination of acid value (AV)

The acid value (AV) of cold pressed oils was determined using the AOCS official method Te 1a-64 (2017). Briefly, 0.5 g of each test sample was dissolved in 12.5 mL of hot (95 ◦C) neutralized ethanol. In the presence of a phenolphthalein indicator, sample mixtures were titrated against 0.1 N KOH by vigorously shaking until a permanent pink color appeared. The blank was determined concurrently under the same conditions. The free fatty acid (FFA) content of the test sample was calculated using the following formula and expressed as a percentage of palmitic acid.

$$\text{AV }\left(\frac{\text{mg}}{\text{g}}\right)=\frac{\left(\text{Vs}-\text{Vb}\right) \times 56.1 \times \text{ N}}{\text{W}}$$

where Vs (mL): Titration value of sample; Vb (mL): Titration value of blank; N: Normality of KOH; and W (g): Weight of test sample.

$$\text{FFA }\left(\text{\% }\right)=\frac{\text{AV}}{1.99}$$

Determination of peroxide value (PV)

The peroxide value (PV) of the cold pressed oils was estimated using the AOCS Official Method Cd 8b-90 (1990). The test sample was mixed with a solvent mixture of acetic acid and chloroform in a ratio of 3:2 (v/v). After mixing in 1 mL of KI solution, kept in darkness for 1 min while shaking occasionally. Next, 30 mL of distilled water was introduced to the solution and titrated using Na2S2O3 (0.01 N) to release iodine until the yellow hue had nearly disappeared. Subsequently, 1 mL of starch solution (1% w/v) was added to the sample mixture, and titration proceeded with vigorous shaking until the blue color disappeared. The PV was expressed in milliequivalents of O2 per kilogram of oil (mEq O2/kg).

$$\text{PV }\left(\text{meq}\frac{\text{O}2}{\text{kg}}\right)=\frac{\left(\text{Vs}-\text{Vb}\right) \times 1000 \times \text{ N}}{\text{W}}$$

where Vs (mL): Titration value of sample; Vb (mL): Titration value of blank; N: Normality of Na2S2O3; and W (g): Weight of test sample.

Determination of p-anisidine value (p-AV)

The p-anisidine value (p-AV) of cold-pressed oils was determined using the AOCS Official Method Cd 18–90 (1990). Each oil sample (2 g) was diluted with 25 mL of isooctane, and absorbance was measured at 350 nm against the blank isooctane. Then, 5 mL of sample mixture along with isooctane (blank) were combined with 1 mL of p-anisidine solution (0.25%) containing glacial acetic acid (0.25:100, w/v). After 10 min, the absorbance was measured using a spectrophotometer (GENESYS™ 180, Thermo Scientific™, Massachusetts, USA) at 350 nm against a blank containing isooctane and p-anisidine. The p-AV was calculated using the following formula.

$$\text{p}-\text{AV}=\frac{\left(1.2 \times \text{ A}2-\text{A}1\right) \times 25}{\text{W}}$$

where A1: Absorbance value of sample in isooctane; A2: Absorbance value of sample in isooctane containing p-anisidine; and W (g): Weight of test sample.

Determination of conjugated dienes (CD) and conjugated trienes (CT)

The conjugated dienes (CD) and conjugated trienes (CT) present in cold pressed oils were determined according to the AOAC official method Ti 1a-97 (1997). The oil sample was filtered and mixed with hexane at a ratio of 1:100 (v/v). The CD and CT were then determined by measuring the absorbance at 232 and 268 nm, respectively, using a UV–visible spectrophotometer (GENESYS™ 180, Thermo Scientific™, Massachusetts, USA). The percentages of CD and CT in the oils were calculated using the following formula.

$$\text{CD }\left(\text{\%}\right)=\frac{\text{A}\left(\uplambda 232\right) }{\upomega }\text{ CT }\left(\text{\%}\right)=\frac{\text{A}\left(\uplambda 268\right) }{\upomega }$$

where A (λ232): Absorbance value of sample at 232 nm; A(λ268): Absorbance value of sample at 268 nm; and ω (g/100 mL): Concentration of oil.

Determination of total oxidation index (TOTOX)

The TOTOX value is an important measure of oxidative degradation in oils and was calculated using the formula15.

TOTOX = (2 × PV) + p-AV.

Where PV: Peroxide value; and p-AV: para-anisidine value.

Determination of saponification value (SV)

The saponification value (SV) of cold-pressed oils was determined by following AOCS Official Method Cd 3c-91 (2017). The test samples (2 g) were dissolved in 25 mL of alcoholic KOH. Saponification was then accomplished by gently boiling in a water bath for 30 min. After cooling, 10 mL of hot ethyl alcohol and 1 mL of the phenolphthalein indicator were combined. The SV value of oils was determined by titrating them against 0.5N HCl to remove excess KOH, which appeared as a cloudy solution. The SV was calculated using the following formula and expressed as mg of KOH required to saponify 1 g of oil.

$$\text{SV }\left(\frac{\text{mg}}{\text{g}}\right)=\frac{\left(\text{Vb}-\text{Vs}\right) \times \text{ N }\times 56.1}{\text{W}}$$

where Vs (mL): Titration value of sample; Vb (mL): Titration value of blank; N: Normality of HCl; and W (g): Weight of test sample.

Determination of iodine value (IV)

The iodine value (IV) is used to measure the degree of unsaturated fatty acids in oil. In the present study, IV of cold pressed oils was determined based on their fatty acid composition using the following formula and expressed as a number of grams of I2 absorbed by 100 g of oil16.

IV = (% C16:1 × 0.95) + (% C18:1 × 0.86) + (% C18:2 × 1.732) + (% C18:3 × 2.616).

Determination of total carotenoid content (TCC)

The total carotenoid content (TCC) of cold pressed oils was estimated using the spectrophotometric method17. Five grams of each test sample was dissolved in 100 mL of cyclohexane. The absorbance of the resulting sample mixture was then measured at 445 nm using a UV–visible spectrophotometer (GENESYS™ 180, Thermo Scientific™, Massachusetts, USA), with the blank cyclohexane as a reference. The results were expressed as mg of β-carotene equivalent (BCE)/kg of oil.

$$\text{TCC }\left(\text{ppm}\right)=\frac{\left(\text{As}-\text{Ab}\right) \times 383}{\text{W}}$$

where, As: Absorbance of sample; Ab: Absorbance of blank; 383: Extinction coefficient for carotenoids; and W (g): Weight of sample.

Determination of total phenol content

The total phenolic content (TPC) of cold pressed oils was determined using Folin–Ciocalteu method18. Three grams of each test sample was dissolved in 15 mL of hexane, followed by extraction with methanol and water (80:20, v/v) solvent, each time by vortexing. The content was centrifugation at 3500 rpm for 10 min to facilitate phase separation. The methanolic fraction containing polar extracts was separated and washed with hexane to remove any residual oil. 2 mL of extract was diluted with Folin-Ciocalteu reagent (0.5 mL) and incubated for 3 min. Later, 10% of saturated sodium carbonate (1 mL) solution was added, and the volume was adjusted to 10 mL using distilled water. The samples were then allowed to stand for 1 h in the dark at room temperature. The absorbance of samples was measured at 725 nm against the blank using a UV–visible spectrophotometer (GENESYS™ 180, Thermo Scientific™, Massachusetts, USA). The TPC of cold pressed oils was calculated from gallic acid (≥ 98.0%, Sigma-Aldrich) standards and expressed as mg of gallic acid equivalents (mg GAE/100 g oil).

The equation of the gallic acid standard curve: y = 0.0056x + 0.0311 (R2 = 0.9975).

Determination of total flavonoid content (TFC)

The total flavonoid content (TFC) of cold pressed oils was determined by the aluminum chloride method19. Methanolic extract of each sample was diluted with 4 mL of distilled water and 0.3 mL of 5% (w/v) sodium nitrate. After 5 min, 0.6 mL of 10% (w/v) aluminum chloride was added and incubated for 6 min before adding 2 mL of NaOH (1N) solution. Later, the volume was adjusted to 10 mL with distilled water, and the absorbance of the extract was measured using a UV–visible spectrophotometer (GENESYS™ 180, Thermo Scientific™, Massachusetts, USA) at 510 nm against the blank. The TFC of cold pressed oils was calculated from catechin (≥ 99.0%, Sigma-Aldrich) standards and expressed as mg of catechin equivalent (mg CE/g oil).

The equation of the catechin standard curve: y = 0.0109x + 0.03 (R2 = 0.9781).

Determination of in vitro antioxidant potential

The antioxidant capacity of cold pressed oils was estimated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH)-free radical scavenging assay19. One mL of methanolic oil extract was combined with 0.06 µM of freshly prepared DPPH solution in methanol. After 30 min of incubation at room temperature, the absorbance of the samples and control (DPPH solution) was measured at 517 nm against blank methanol (GENESYS™ 180, Thermo Scientific™, Massachusetts, USA). The following formula was used to calculate the percentage inhibition of radical scavenging activity (RSA).

$$\text{\% Inhibition}=\frac{\left(\text{Ac}-\text{As}\right)}{\text{Ac}} \times 100$$

where Ac: Absorbance of control; and As: Absorbance of sample.

Determination of in vitro anti-inflammatory potential

The in vitro anti-inflammatory potential of cold pressed oils was determined by using a modified bovine serum albumin (BSA) thermal denaturation inhibition assay20. The method was modified as follows: a stock solution of 20% of each oil sample was prepared in dimethyl sulfoxide (DMSO). 1% (w/v) of BSA solution was prepared in 0.05 M Tris–phosphate saline buffer, and pH was adjusted to 6.5 using glacial acetic acid. To evaluate the anti-inflammatory potential, the reaction mixture of 5 mL consisted of 3 mL of Tris–phosphate buffer saline solution (0.05 M, pH 6.5), 1 mL of BSA, and 1 mL of varying concentrations of oil extracts prepared by serial dilutions (0.625, 1.25, 2.5, 5, 10, and 20%). The control consisted of 1 mL of DMSO instead of the test sample. The reaction mixtures were incubated at 37 ± 2 °C for 15 min and then heated to 70 °C for 5 min. After cooling, the absorbance of the tested samples was measured using a UV/Vis spectrophotometer (GENESYS™ 180, Thermo Scientific™, Massachusetts, USA) at 660 nm using DMSO as a blank. The sucrose was used as a positive control. The results were expressed as percentage inhibition of protein thermal denaturation and calculated using the following equation:

$$\text{\% Inhibition of protein denaturation}\frac{\left(\text{Ac}-\text{As}\right)}{\text{Ac}} \times 100$$

where Ac: Absorbance of control, and As: Absorbance of sample.

Determination of phosphorus content

The total phosphorus content of cold pressed oils was estimated using the modified triacid extract vanadomolybdate method21. One mL of oil sample was mixed with 100 mL of distilled water and treated with 5 mL of a triple acid combination consisting of sulfuric (H2SO4), nitric (HNO3), and perchloric acid (HClO4) in a ratio of 2:9:1 to extract phosphorus. Then, 5 mL of triple acid extract was combined with 5 mL of Barton’s reagent (a solution containing ammonium molybdate and ammonium metavanadate in nitric acid), and the volume was made to 25 mL using water. The solution mixture was allowed to stand for 30 min until it turned yellow. The intensity of color formed was measured at 470 nm using a spectrophotometer (GENESYS™ 180, Thermo Scientific™, Massachusetts, USA). The phosphorus content of cold pressed oils was determined using a standard curve prepared with various phosphorus concentrations.

Statistical analysis

Descriptive statistics of parameters were graphically represented using a bar plot wherein the error bar represents the standard deviation (± SD) for the mean of three replications (n = 3), with a significant difference at P < 0.05. Analysis of variance (ANOVA) was performed on three independent measurements using SPSS. The principal component analysis (PCA) and Pearson correlation (r) analysis were used as a statistical measure that indicates the strength of association and direction of linear relationship between two continuous variables using the R program. The scores and loadings of data analyzed using PCA were displayed as biplots.

Results and discussion

Fatty acid profile of cold pressed oils

All tested oils showed a huge difference in their fatty acid composition, resulting in differences in total SFA, MUFA, and PUFA (Fig. 1A). The major fatty acids in tested oils were found to be lauric (C12:0), myristic (C14:0), palmitic (C16:0), oleic (C18:1), linoleic (C18:2) and erucic acid (C22:1), The SFAs ranged from 8 to 87%. Palmitic acid and stearic acid were the primary SFAs found in nearly all edible oils. Of all the oils studied, CoO contained the highest level of SFAs (87%), followed by PaO (52%) (Fig. 1B). Nevertheless, the most prevalent SFA in oils examined was lauric acid in CoO (44%), palmitic acid in PaO (45%), and stearic acid in SeO (6%). The CoO, with high SFAs, mostly consists of high amounts of lauric (44.14%) and myristic acid (20.33%) were in agreement with a previous study22. PaO stands out for its balanced fatty acid profile, with an equal proportion of SFAs (50%) and unsaturated fats (50%). Our results on the fatty acid composition of PaO are consistent with the reported range from 42–47% for palmitic acid and 37–41% for oleic acid23,24. The lowest SFAs were detected in AlO and MuO, and both had approximately 8%. SFAs enhance oil quality and stability by resisting oxidation and thermal degradation, while unsaturated fatty acids are vital for human health, reducing LDL cholesterol levels and improving cardiovascular health8.

Fig. 1
Fig. 1
Full size image

Heat map showing fatty acid composition of cold pressed oils (A), with blue indicating higher and yellow indicating lower percentages. Pie charts depict the percentage of saturated (B), monounsaturated (C), and polyunsaturated (D) fatty acids, with color gradients representing values from low (lighter color) to high (darker color).

The highest level of MUFAs was found in AlO with 66% followed by MuO, SeO, PaO, and GnO with 59%, 41%, 41% and 40%, respectively (Fig. 1C). While, the lowest MUFAs were detected in CoO, NiO, and SaO with approximately 8%, 14%, and 15%, respectively. The low SFA and high MUFA content of cold pressed AlO was consistent with previous findings on almond varieties cultivated from Turkey and Serbia25. The oleic acid was the major MUFA in all oils except MuO, for which erucic acid was the major MUFA. These findings were consistent with previous research showing that mustard oil contained high levels of erucic acid (42%), which amounts to 56% of the MUFAs26. The oils with low erucic acid were deemed safe and approved for human consumption, whereas oils with high erucic acid were preferred for industrial applications (Zealand, 2003). Elevated erucic acid levels in children have been associated with lipidosis and a rise in blood cholesterol, leading to myocardial dysfunction and, ultimately, a heart attack27. Similarly, SuO contains high levels of oleic (29.9%) and linoleic acid (58.3%), making up 88.2% of the total fatty acids which were in agreement with previous reports28,29. According to Codex Alimentarius, SuO was grouped into three categories based on oleic acid content: low (14–39.4%), medium (43.1–71.8%), and high (75–90.7%) oleic SuO (WHO, 2015). As per our results, it can be inferred that SuO tested is of low oleic variety.

The highest levels of PUFAs were observed in SaO, NiO, and SuO, making up approximately 74%, 68%, and 54%, respectively (Fig. 1D). Linoleic acid, a major component of the PUFAs, makes up 71–75% of SaO30. The principal PUFA in NiO was linoleic acid, accounting for approximately 68%, consistent with previous findings31,32,33. In addition, MuO had the highest level of linolenic acid at 11%, whereas AlO had the lowest level at < 1% compared to the other tested oils25,26. The PUFA is widely recognized for its essential role in preserving the integrity of skin and cell membranes, as well as in supporting the immune system and production of eicosanoids34. The well-known benefits of ω3-PUFAs (linolenic acid) in reducing inflammation and possibly preventing heart disease, and pro-inflammatory effects of ω6-PUFAs (linolic acid) that can lead to inflammation, are widely recognized (Djuricic and Clader, 2021). Therefore, oils with a balanced ratio of ω6- and ω3- PUFAs are recommended for positive health benefits.

Nutritional quality indices of cold pressed oils

The nutrition quality indices viz., atherogenicity index (AI), thrombogenicity index (TI), and hypo- to hyper-cholesterolemic (HH) fatty acid ratio of cold pressed oils were calculated based on their fatty acid composition (Fig. 2). These indices provide more useful information for evaluating the nutritional value of oils than fatty acid composition. The nutritional quality indices varied among the cold pressed oils that were tested. Our results showed that CoO had the highest levels of AI and TI, with 10.66 and 5.24, respectively, compared to other oils tested. Following CoO, PaO exhibited the highest AI (1.02) and TI (2.12) among all the oils that were examined. Furthermore, the HH index of the CoO was 0.42, which was the lowest among the studied oils, followed by PaO with an HH index of 1.04, indicating their distinct characteristics. The highest levels of AI and TI were observed in cold pressed CoO and PaO, which could be due to high levels of SFAs such as lauric and palmitic acid, respectively. On the other hand, the other tested oils showed low levels of AI (0.2) and TI (0.5), leading to their low SFAs and high unsaturated fats. MuO had the lowest AI and TI, with values of 0.04 and 0.11, respectively. The highest HH value was observed in SuO (14), followed by AlO (13.51) > SaO (13.5) > MuO (13.31) > NiO > (9.1) > SeO (8.81) > GnO (6.4). An earlier study by Ulbricht et al. (1991) reported that CoO, PaO, and SuO had AI values of 13.63, 0.88, and 0.07, respectively, and TI values of 6.18, 2.07, and 0.28, respectively.

Fig. 2
Fig. 2
Full size image

Cone graph showing the atherogenicity (AI), thrombogenicity index (TI), and hypo- to hyper-cholesterolemic (HH) fatty acid ratio of cold pressed oils, based on fatty acid composition.

Over time, there has been intense debate over whether a diet rich in SFAs is associated with cardiovascular diseases. Although atherogenic and thrombogenic SFAs can lead to cardiovascular disease, MUFAs, PUFAs, dietary fibers, and antioxidants have a protective function (Ulbricht et al., 1991). However, several studies have suggested that SFAs with a carbon chain of ≤ C10 are unlikely to elevate cholesterol levels, while long-chain SFAs are believed to potentially increase the risk of atherosclerosis and blood clot formation more quickly than unsaturated fats35,36,37. In particular, it is the longer-chain SFAs like lauric, myristic, and palmitic acids that induced thrombogenicity in rats, leading to platelet aggregation triggered by thrombin37. Moreover, it is important to note that the stereotypic distribution of fatty acids within triacyl glycerides (TAGs) has a significant effect on their metabolic fate during digestion and absorption. In PaO, 70% of the Sn-1 and Sn-3 positions of TAGs are predominantly esterified with palmitic acid while the Sn-2 position is mainly esterified with oleic and linoleic acid38. Therefore, the nutritional value of oils is determined by not only their composition but also the stereospecific distribution of fatty acids in TAG. Hence, oils such as PaO, which have a balanced ratio of SFAs and MUFAs, are also considered to have high nutritional value due to the stereospecific distribution of unsaturated fats in the Sn-2 position23.

Iodine value of cold pressed oils

Iodine value (IV) is used to assess oil stability to oxidation, the extent to which a product has been adulterated, and the degree of unsaturation in oils. The IV for cold pressed oils ranged from 15 to 141 (Fig. 3A). The lowest IV was observed in CoO (15), aligning with a previous study that reported a range of 5 to 14 (Idu et al., 2020). On the other hand, the highest IV value was recorded for SaO (141), which was lower than the previously reported range of 166 to 190 across different cultivars7. Furthermore, SuO (123), GnO (104), MuO (79), and NiO (131) had IV consistent with previous results of 127, 111, 95, and 132, respectively39,40,Pardeshi et al., 2020; Bhatnagar & Gopala, 2015). Similarly, IV of SeO (110) and PaO (48) were consistent with earlier studies which reported IV ranging from 60 to 112 and 40 to 57, respectively (Davoodi et al., 202041;. The IV of the cold pressed AlO was approximately 102 and ranged from 96 to 10142. Therefore, the iodine value (IV) observed in the present study showed a positive correlation with the degree of unsaturation in the oils, as reflected in their fatty acid composition (Fig. 1).

Fig. 3
Fig. 3
Full size image

Biochemical and oxidative properties of cold pressed oils: (A) iodine value (IV), (B) saponification value (SV), (C) acid value (AV), (D) free fatty acid (% oleic acid), (E) peroxide value (PV), (F) para-anisidine value (p-AV), (G) total oxidation state (TOTOX), (H) conjugated dienes (CD), and conjugated triene (CT). Data expressed as mean ± SD of three replications (n = 3).

Saponification value of cold pressed oils

The saponification value (SV), an indicator of the average molecular weight of fatty acids in oils, ranged from approximately 163 to 231 mg KOH/g in the cold-pressed oils analyzed (Fig. 3B). MuO exhibited the lowest SV (163 mg KOH/g), while CoO showed the highest (231 mg KOH/g), consistent with previous findings by Pardeshi et al. (2020) and Idu et al.22, respectively. PaO (218 mg KOH/g) and SaO (210 mg KOH/g) also displayed high SVs, aligning with values reported by Song et al.7 and Raji et al.41. NiO presented a higher SV than previously reported by Bhatnagar & Gopala (2015), likely due to genotypic variation affecting fatty acid composition. The SV values for AlO, SeO, and GnO were consistent with earlier studies43,44,45, indicating strong agreement across different data sources.

Acid value of cold pressed oils

The acid value (AV) of the cold-pressed oils ranged from approximately 0.3 to 11 mg KOH/g, with corresponding free fatty acid (FFA) levels between 0.23% and 5.88% (Fig. 3C and 4D). Most oils fell within the permissible limits set by Codex standards for cold-pressed oils, indicating stability and suitability for consumption. PaO exhibited the highest AV (11.8 mg KOH/g), slightly exceeding the Codex limit of 10 mg KOH/g for virgin PaO. However, this value aligns with reports by Bahadi et al.46, who observed AVs as high as 19–21 mg KOH/g. In contrast, SuO showed the lowest AV (0.47 mg KOH/g), consistent with earlier findings that highlight AV variability due to genotype and environmental factors (Kostadinovic & Mitrev, 201328).

Fig. 4
Fig. 4
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(A) Total carotene content (TCC), (B) total phenolic content (TPC), (C) total flavonoid content (TFC), (D) in vitro antioxidant activity, and (E) total phosphorus content of nine cold pressed vegetable oils. Data expressed as mean ± SD of three replications (n = 3).

AlO had an AV of 1 mg KOH/g, aligning with the reported range of 1.17–2.21 mg KOH/g for cold-pressed AlO44, and slightly higher than the values observed in solvent-extracted oils. CoO displayed an AV of 3.3 mg KOH/g, which is comparable to values reported for cold-pressed CoO and slightly higher than its hot-pressed counterpart22. SeO had an AV of 1.4 mg KOH/g, marginally exceeding the previously reported range of 0.86–1.12 mg KOH/g43. Variations in AV across the oils may result from differences in raw material quality, harvest timing, storage, seed handling, and extraction methods11.

Peroxide value of cold pressed oils

The peroxide value (PV) of the cold-pressed oils ranged from approximately 5 to 22 mEq O₂/kg (Fig. 3E). Most oils fell within the Codex (1999) permissible limit of ≤ 15.00 mEq O₂/kg for virgin and cold-pressed oils, indicating good quality and low levels of primary oxidation. The lowest PVs were observed in AlO (4.66 mEq O₂/kg) and CoO (4.79 mEq O₂/kg), suggesting minimal oxidation, consistent with previous findings44,47. PaO had a PV of 13 mEq O₂/kg, which is within expected limits, though previous studies have reported higher values under different storage conditions48.

SuO (9.29 mEq O₂/kg), GnO (7.08 mEq O₂/kg), and MuO (9.07 mEq O₂/kg) also remained within acceptable limits, with minor deviations compared to earlier research39,Pardeshi et al., 2020). SeO and SaO exhibited slightly elevated PVs, likely influenced by genetic and storage-related factors49,50. NiO, however, exceeded the Codex limit with a PV of 22.36 mEq O₂/kg, potentially due to increased moisture content or light exposure, as suggested by Bhatnagar & Gopala (2014). Overall, while most oils demonstrated acceptable oxidative stability, variations in PV were evident and may be attributed to differences in processing, storage, and oil composition.

Para-anisidine value of cold pressed oils

The p-Anisidine value (p-AV) of the tested cold-pressed oils ranged from 0.02 to 6 (Fig. 3F). A low p-AV indicates minimal secondary oxidation; however, it alone may not reflect overall oil quality, as hydroperoxides decompose into more stable aldehydes and ketones during secondary oxidation51. Therefore, p-AV should be interpreted alongside the PV for a comprehensive assessment of oxidative stability. In this study, most oils had a p-AV ≤ 0.5, suggesting minimal secondary oxidation and good quality. CoO had the lowest p-AV (0.02), indicating negligible oxidation, while PaO recorded the highest (6), reflecting substantial oxidation. The p-AV values of SeO (0.22) and SaO (0.13) aligned with previous reports52,53, whereas SuO (0.09) showed a lower value than earlier findings40. AlO and CoO exhibited lower p-AVs compared to prior studies44,54. Similarly, crude GnO and MuO had lower p-AVs than previously reported, likely due to differences in storage and extraction methods (Roshni et al., 2019,Pardeshi et al., 2020. Overall, the results confirm that most of the oils analyzed underwent minimal secondary oxidation, supporting their high quality.

Total oxidation index of cold pressed oils

The TOTOX index, which combines peroxide value (PV) and p-Anisidine value (p-AV), provides a comprehensive measure of both primary and secondary oxidation, reflecting the overall oxidative stability of oils (Roshni et al., 2019). In this study, the TOTOX index of cold-pressed oils ranged from approximately 9 to 45 (Fig. 3G). Most oils showed values between 10 and 20, indicating early signs of oxidation. A TOTOX index below 10 is indicative of fresh, high-quality oil, while values between 10 and 20 suggest the onset of oxidation; values above 20 denote rancidity and unsuitability for culinary use55. AlO (9.43) and CoO (9.6) had the lowest TOTOX indices, reflecting low levels of both PV and p-AV and confirming their superior quality. The TOTOX value of AlO was consistent with previous reports (8–9).

In contrast, NiO (45) and PaO (32) exhibited the highest TOTOX indices due to elevated PV and p-AV, indicating significant oxidation and poor quality, likely stemming from the presence of aldehydes and hydroperoxides in unrefined oils. SuO (19) and MuO (19) had higher TOTOX values than reported in earlier studies (Gagour et al., 202240,56,), possibly due to variations in hybrids or pre-pressing treatments. Similarly, GnO (14) showed a higher TOTOX index compared to the previous study by El et al. (2023), which may be attributed to seed processing methods such as roasting. The TOTOX index of SaO (14) fell within the range previously reported by Longoria-Sanchez et al.57, suggesting moderate oxidation. Overall, oils with TOTOX values above 20 exhibited signs of spoilage, while those below this threshold retained acceptable quality.

Conjugated dienes and conjugated trienes of cold pressed oils

The K232 and K268 extinction coefficients are important indicators of primary and secondary oxidation in oils, representing the presence of conjugated fatty acid dienes (CD) and trienes (CT), respectively58. In this study, K232 values ranged from 1.23 to 3.87, and K268 values from 0.02 to 1.74 (Fig. 3H), reflecting varying levels of oxidation across cold-pressed oils. CoO exhibited the lowest K232 (1.23) and K268 (0.02) values, correlating with its low PV, p-AV, and TOTOX indices, indicating minimal oxidation. However, these values were slightly higher than those previously reported by Sharanke & Sivakanthan59. In contrast, NiO showed the highest K232 (3.87) and K268 (1.74) values, suggesting advanced oxidation and poor quality, supported by its elevated PV, p-AV, and TOTOX indices.

Other oils with high extinction values included SaO (K232 = 3.54; K268 = 0.93), SuO (K232 = 3.17; K268 = 0.27), and MuO (K232 = 3.17; K268 = 0.39), while PaO showed intermediate values (K232 = 1.83; K268 = 0.71). These findings align with previous studies that observed similar trends in fresh cold-pressed oils (Bhatnagar & Gopala, 201552;). Oils with high PUFA content tend to have elevated K232 and K268 values due to increased formation of CD and CT during oxidation58. AlO (K232 = 2.37,K268 = 0.11) and GnO (K232 = 0.9–2.2; K268 = 0.02–0.18) showed values consistent with earlier reports60,El et al., 2023). A positive correlation was observed between higher K232 and K268 values and increased oxidation indicators (PV, p-AV, TOTOX), suggesting that antioxidants in cold-pressed oils may limit CT formation and enhance oxidative stability. Conversely, impurities in mechanically pressed oils could contribute to elevated oxidation products, resulting in higher extinction values.

Total carotene content of cold pressed oils

The total carotenoid content (TCC) of cold-pressed oils showed considerable variation, ranging from approximately 3 mg BCE/kg in CoO to 812 mg BCE/kg in PaO (Fig. 4A). CoO had the lowest TCC (3 mg BCE/kg), followed by AlO (6 mg BCE/kg) and GnO (9 mg BCE/kg). These low values are in line with earlier reports, though GnO exhibited slightly higher TCC than previously documented, possibly due to genotypic and processing differences39,El et al., 2023). AlO and GnO’s TCC values were consistent with earlier findings (0.68 and 0.42 mg BCE/kg, respectively) (Al et al., 2018), though GnO again showed a higher value than expected.

Most other oils had modest TCC values, averaging around 15 mg BCE/kg. SuO and MuO displayed slightly elevated TCC compared to previous reports (3 and 19 mg BCE/kg, respectively)39, reinforcing the influence of genotype and extraction method on carotenoid levels. NiO had a TCC of 13 mg BCE/kg, lower than the 40.5 mg BCE/kg reported by Bhatnagar & Gopala (2015), but in agreement with Deme et al.31, who observed a range of 2 to 8 μmol/g. SaO exhibited a TCC of 15 mg BCE/kg, below the 8 to 20 mg/g range found in earlier studies (Ben et al., 2015). PaO stood out with the highest TCC (812 mg BCE/kg), followed by MuO (102 mg BCE/kg). PaO’s carotenoid levels have been reported to range from 200 to 1600 mg BCE/kg depending on genotype61, underscoring its value as a rich source of carotenoids. This wide variability highlights the critical role of genetic background and production conditions in determining carotenoid content in cold-pressed oils61,62.

Total phenolic content of cold pressed oils

The total phenolic content (TPC) of cold-pressed oils varied widely, ranging from 1.68 mg GAE/100 g in AlO to 30 mg GAE/100 g in SeO (Fig. 4B). AlO exhibited the lowest TPC, consistent with earlier findings (Al et al., 2018), while SeO showed the highest (133 mg GAE/kg), aligning with reports by Kostadinovic & Mitrev (2013). Oils such as PaO (22.56 mg GAE/100 g), SaO (21.27 mg GAE/100 g), and MuO (10.26 mg GAE/100 g) also displayed relatively high TPC levels. Notably, PaO’s TPC exceeded values reported for crude palm oil63, suggesting its higher antioxidant content may contribute to reduced levels of oxidation products (CD and CT). MuO’s TPC was in line with the 14–30 mg SAE/g range reported by Thiyam-Holländer et al.64, while SaO’s values (80–144 mg/kg, genotype-dependent) agreed with Ben et al. (2015).

Conversely, NiO (7.21 mg GAE/100 g), CoO (5.31 mg GAE/100 g), GnO (3.98 mg GAE/100 g), and SuO (3.87 mg GAE/100 g) had TPCs below 10 mg GAE/100 g. CoO’s value aligned with findings by Mudiyanselage & Wickramasinghe65, while SuO’s (61 mg GAE/kg) was consistent with Kostadinovic & Mitrev (2013). GnO’s TPC obtained by cold pressing (5.31 mg GAE/100 g) was lower than Soxhlet extraction (6.84 mg/100 g), likely due to better solubility of phenolics in solvents66. The observed variation in TPC across oils highlights the influence of genotype, extraction methods, and processing conditions on phenolic content. Higher TPC values in oils like SeO and PaO underscore their antioxidant potential, with SeO’s phenolic profile strongly associated with its antioxidant capacity (Kostadinovic & Mitrev, 2013). These findings reinforce the role of processing techniques in shaping both phenolic content and oxidative stability in cold-pressed oils.

Total flavonoid content of the cold pressed oils

Figure 4C illustrates the total flavonoid content (TFC) of cold-pressed oils, ranging from 0.03 to 1.58 mg CE/g of oil. AlO exhibited the lowest TFC (0.03 mg CE/g), aligning with earlier reports (1.13 mg/100 g; Al et al., 2018). In contrast, PaO showed the highest TFC (1.58 mg CE/g), which correlated with its lower CT values and reduced levels of oxidation products. However, this value was notably lower than the 18 mg QE/g reported for crude palm oil63. CoO (1.44 mg CE/g) and SeO (1.27 mg CE/g) also demonstrated high flavonoid content. CoO’s TFC exceeded earlier findings (10–20 mg QE/100 mL67), while SeO’s value aligned with Hamitri et al. (2020), who observed higher quercetin levels in cold-pressed SeO (2.5 mg QE/100 mL) compared to its refined counterpart (1.2 mg QE/100 mL).

Other oils exhibited moderate to low TFC levels: NiO (0.72 mg CE/g), MuO (0.62 mg CE/g), GnO (0.59 mg CE/g), SaO (0.27 mg CE/g), and SuO (0.16 mg CE/g). NiO’s TFC was higher than the range previously reported for Niger seed (5.32–15.98 μg/g; Padhi et al., 2023). MuO’s TFC (4 mg QE/g for white and 6 mg QE/g for black variants) showed some deviation but remained within expected values68. SaO’s TFC was notably lower than the 4.60–7.25 mg/g range reported for various safflower genotypes69. The wide variation in TFC among oils underscores their differing antioxidant capacities. PaO, despite being lower than previously reported values, exhibited the highest flavonoid content among the tested oils, enhancing its antioxidant potential. CoO and SeO also stood out with substantial flavonoid levels, with SeO maintaining higher quercetin content relative to refined versions. Moderate TFC values observed in NiO, MuO, and GnO could be attributed to differences in genotype, extraction method, or environmental conditions. These results highlight the intricate interplay between oil composition, extraction practices, and cultivation factors in shaping the antioxidant profiles of cold-pressed oils.

Antioxidant potential of cold pressed Oils

Figure 4D shows that the antioxidant activity of cold-pressed oils ranged from 33 to 81 mg TE/kg. Among the oils, PaO exhibited the lowest activity (32.65 mg TE/kg), while CoO had the highest (80.75 mg TE/kg). High antioxidant activities were also recorded in SeO (76 mg TE/kg), SaO (72 mg TE/kg), SuO (65 mg TE/kg), MuO (64 mg TE/kg), AlO (63 mg TE/kg), NiO (59 mg TE/kg), and GnO (47 mg TE/kg).

These findings differ from previous reports; for example, Kumar and Krishna70 noted scavenging activities for CoO ranging from 11 to 50%. Similarly, cold-pressed SeO (74%) exhibited higher activity than the 24% for refined SeO and 35% for unrefined SeO reported by Hamitri et al. (2020). The antioxidant activity of AlO (56%) was also greater than the 27.81% inhibition previously observed, and GnO’s activity (32%) exceeded the 11.43% reported by Al et al. (2018). For GnO, variations in activity—from 7 to 50%—have been attributed to differences in pre-pressing treatments, such as roasting (El et al., 2023). NiO’s activity (50%) was consistent with earlier studies that highlighted enhanced scavenging for solvent-extracted oils rich in bioactive compounds like tocopherols, phenolics, sterols, and carotenoids (Bhatnagar & Gopala, 2014).

Overall, the variation in antioxidant activity can be attributed to agronomic, genetic, and environmental conditions, as well as differences in processing and extraction methods. CoO’s superior performance underscores the potential advantages of cold-pressed over refined oils, while the high activity of SeO further illustrates the benefits of using unrefined oil. Additionally, the improved antioxidant potentials observed for AlO and GnO, alongside the influence of pre-pressing treatments and extraction solvents, emphasize the importance of standardized methodologies for accurately assessing and comparing the antioxidant properties of cold-pressed oils.

Total phosphorus content of cold pressed oils

Phosphorus in vegetable oils is predominantly found as phospholipids, and its concentration is influenced by both the source of the oil and the extraction method used. In this study, the total phosphorus content of cold-pressed oils (Fig. 4E) ranged from 176 ppm in MuO to about 472 ppm in PaO. All the oils, being unrefined and cold-pressed, demonstrated relatively high phosphorus levels, with PaO recording the highest (472 ppm), followed by GnO (311 ppm). NiO and SeO each had phosphorus contents around 243 ppm.

The elevated phosphorus levels, especially in PaO, are likely due to its high phospholipid content, a trait common in crude and unrefined oils. Phospholipids in such oils are often associated with FFAs and trace metals, which can compromise oil quality by affecting its stability, color, and flavor71. In the case of PaO, the moisture present in the mesocarp may contribute to the formation of hydratable phospholipids, which can become insoluble in the oil72. This aligns with observations by Gibon et al.73, who reported that phosphorus in PaO exists largely as inorganic phosphates, with phosphatides making up 10–30% of the total phosphorus content. The phosphorus content in other oils was also notable: AlO and SaO had 216 ppm, SuO contained 190 ppm, and CoO 210 ppm. These values confirm that phospholipids are significant components across various cold-pressed oils, not just in PaO.

Given that high phosphorus levels often exceed 10 ppm are undesirable in edible oils due to their adverse effects on processing and stability, refining steps like degumming are essential. As recommended by Cesarini et al.74, effective degumming is crucial to reduce phosphorus levels to below 10 ppm, thereby enhancing oil quality and safety. These results underscore the importance of degumming, especially for oils intended for consumption, as phospholipids not only affect physical properties but can also interfere with further refining processes and shorten shelf life.

In vitro anti-inflammatory potential of cold pressed oils

The anti-denaturation potential of cold-pressed oils decreased with increasing concentration of extract, as shown in Table 1. The concentration of extract from 0.625 to 5 mg/mL increased the anti-denaturation of protein in AlO from 19 to 60%, but decreased beyond 5 mg/mL. Most of the oils showed anti-denaturation potential at concentrations below 0.625 mg/mL. PaO exhibited the highest anti-denaturation at 66%, while NiO showed the lowest at 13%. Increasing concentrations above 0.625 mg/mL led to a decrease in the anti-denaturation potential. After PaO, CoO, and SeO exhibited the higher anti-denaturation potential of 42% and 31%, respectively, at 0.625 mg/mL. Inflammation is a complex biological response to harmful stimuli and involves various physiological processes such as redness, heat, and pain75. Protein denaturation plays a significant role in the inflammatory response, as denatured proteins can contribute to cellular dysfunction. Non-steroidal anti-inflammatory drugs (NSAIDs) are known to inhibit protein denaturation and the cyclooxygenase (COX) enzyme76, providing evidence for the potential therapeutic effect of inhibiting protein denaturation in inflammation.

Table 1 Bovine serum albumin thermal denaturation inhibition (anti-inflammatory) potential of DMSO extracts from nine different cold pressed vegetable oils.
Full size table

Cold-pressed oils retain bioactive compounds such as phenols, flavonoids, tocopherols, and carotenes, which are believed to have anti-inflammatory properties. In particular, tocotrienols from PaO have been reported to exhibit anti-inflammatory effects by reducing oxidative stress, modulating inflammatory pathways, and protecting against infection77. Additionally, the bioactive compounds in PaO may help mitigate protein denaturation by interacting with proteins, maintaining their original structure and function. Our study demonstrates that DMSO extracts of cold-pressed oils exhibit concentration-dependent anti-denaturation properties. PaO exhibited the strongest anti-denaturation potential, likely due to its high bioactive compound content, followed by CoO and SeO. These results suggest that cold-pressed oils may provide beneficial effects in preventing protein denaturation, a key factor in inflammation. Further research is necessary to fully explore the mechanisms behind these effects and evaluate the therapeutic potential of these oils in inflammation-related diseases.

Principal component analysis

Principal component analysis (PCA) was conducted on a matrix comprising the phytochemical, nutritional, and antioxidant properties of the studied cold-pressed oils. The PCA biplot (Fig. 5) illustrates the relationships between the nine cold-pressed oils and dependent variables, such as MUFAs, PUFAs, TCC, p-AV, FFA, AV, TFC, TPC, TOTOX, PV, CT, CD, AI, TI, IV, SP and DPPH radical scavenging activity.

Fig. 5
Fig. 5
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Principal component analysis biplot of scores and loadings for phytochemical, nutritional, and antioxidant properties of nine cold pressed oils. Variables include TCC (total carotene content), p-AV (para-anisidine value), FFA (free fatty acid), AV (acid value), TFC (total flavonoid content), TPC (total phenolic content), TOTOX (total oxidation state), PV (peroxide value), CT (conjugated triene), CD (conjugated diene), AI (atherogenicity index), TI (thrombogenicity index), HH (hypo-to-hyper-cholesterolemia ratio), IV (iodine value), SP (saponification value), EV (ester value), SFAs (saturated fatty acids), MUFAs (monounsaturated fatty acids), PUFAs (polyunsaturated fatty acids), and DPPH (2,2-diphenyl-1-picrylhydrazyl method).

The first two principal components, PC1 and PC2, accounted for 72.2% of the total variance in the dataset (PC1 = 46.2%, PC2 = 26%). PC1 exhibited negative correlations with MUFAs (−0.0508), PUFAs (−0.2684), IV (−0.2846), HH (−0.3014), PV (−0.0526), TOTOX (−0.0091), CD (−0.2701), and CT (−0.0786). It was positively correlated with the AI (0.1982), TI (0.2619), SFAs (0.2859), and SV (0.2411). Similarly, PC2 was positively correlated with DPPH radical scavenging activity (0.2969), while it was inversely related to TPC (−0.1946), TFC (−0.0357), TCC (−0.2620), p-AV (−0.2652), phosphorus content (−0.2663), FFA (−0.1908), and AV (−0.1908).

The PCA biplot results indicate a clear distinction between the studied oils based on their phytochemical, nutritional, and antioxidant characteristics. The clustering of the oils suggests that their botanical origin and the materials used significantly influence their overall profile. The positive correlations of PC1 with SFAs, AI, TI, and SV highlight the oils with higher concentrations of saturated fatty acids, while the negative correlations with MUFAs, PUFAs, IV, and TOTOX indicate oils that may be more susceptible to oxidation but provide greater antioxidant potential. On the other hand, PC2’s positive correlation with DPPH-free radical scavenging activity and negative correlations with TPC, TFC, and TCC suggest a division in oils based on their antioxidant capacity and phenolic content. These findings demonstrate that the studied oils can be grouped into four distinct categories, which align with differences in their source material and botanical origin. This classification offers insights into how the phytochemical and nutritional properties, along with antioxidant capacity, vary across different oils, providing a basis for selecting oils based on specific health benefits or applications.

Correlation analysis among properties of cold pressed oils

Pearson correlation analysis was performed to examine the degree of linear relationships among the phytochemical, nutritional, and antioxidant properties of the cold-pressed oils. The relatively low correlation coefficients observed between MUFA, PUFA, IV, HH, PV, TOTOX, CD, and CT in the principal component analysis suggest that these variables contribute independently and may have complex, less direct interactions in the overall variability among cold pressed oils. However, the results revealed significant correlations between several parameters, as shown in Fig. 6. A significant positive correlation (p < 0.05) was found between the HH ratio and the PUFAs, IV, and CD values. This indicates that oils with higher PUFAs, IV, and CD values may have a more favorable effect on cholesterol regulation. Additionally, CT showed a highly significant positive correlation (p < 0.01) with PV and TOTOX, suggesting that oils with higher CT may also exhibit higher oxidation levels, which could impact their shelf life and nutritional stability. On the other hand, TCC displayed a highly significant positive correlation with p-AV, FFA, AV, and phosphorus content. This suggests that oils with higher TCC may also exhibit higher p-AV and phosphorus content, which could influence their oxidative stability and potential health effects. Furthermore, a negative correlation was observed between TFC and HH, DPPH radical scavenging activity, and phosphorus content. This indicates that oils with higher TFC may have lower levels of HH and phosphorus, as well as reduced antioxidant activity.

Fig. 6
Fig. 6
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Pearson correlation analysis showing the correlation coefficients and associations between oil parameters. Positive correlations are highlighted in blue, and negative correlations in red. Significant values are indicated as *P < 0.05, **P < 0.01, ***P < 0.001, with ns denoting non-significance. Variables include TCC (total carotene content), p-AV (para-anisidine value), FFA (free fatty acid), AV (acid value), TFC (total flavonoid content), TPC (total phenolic content), TOTOX (total oxidation state), PV (peroxide value), CT (conjugated triene), CD (conjugated diene), AI (atherogenicity index), TI (thrombogenicity index), HH (hypo-to-hyper-cholesterolemia ratio), IV (iodine value), SP (saponification value), EV (ester value), SFAs (saturated fatty acids), MUFAs (monounsaturated fatty acids), PUFAs (polyunsaturated fatty acids), and DPPH (2,2-diphenyl-1-picrylhydrazyl).

TI showed a negative correlation with HH, CD, PUFAs, and IV at a significant difference (p < 0.01), which suggests that oils with higher TI may have a different antioxidant and stability profile compared to those with lower TI values. These results highlight the intricate relationships between the various phytochemical, nutritional, and antioxidant properties of cold-pressed oils. The observed correlations provide a deeper understanding of how these properties interrelate, which is crucial for selecting oils based on their health benefits, oxidative stability, and nutritional quality.

Conclusion

In the current study, we compared the phytochemical, nutritional, in vitro antioxidant, and anti-inflammatory properties of nine different cold pressed oils. This study stands out by integrating comprehensive fatty acid profiling with a robust evaluation of minor bioactive compounds such as phenolics, flavonoids, carotenoids, and phosphorus content using validated analytical methods, including GC-FID, spectrophotometric assays, and antioxidant activity assays, thereby providing a multidimensional assessment of cold-pressed oil quality and health implications that has been scarcely addressed in prior literature. We estimated the nutritional value and quality indices such as atherogenicity index, thrombogenicity index, and hypo- to hyper-cholesterolemic fatty acid ratio in cold pressed oils. Typically, these indices are largely derived from the fatty acid composition of cold pressed oils. However, cold pressed oils also contain several other minor bioactive compounds that possess a variety of beneficial roles in the biological system. For instance, PaO contains exceptionally high carotene content in addition to a balanced saturated-to-unsaturated fatty acid ratio, providing added nutritional and health benefits to human beings. Similarly, SeO is characterized by high phenolic and flavonoid content, resulting in strong DPPH anti-radical scavenging properties that improve oxidative stability and oil quality. Furthermore, these compounds protect unsaturated fatty acids from oxidative damage. Interestingly, our results also demonstrated that cold pressed oils can significantly contribute to the anti-inflammatory properties. Thus, minor components of the cold pressed oils played a crucial role in determining the overall nutritional quality and stability of oils. The quality of cold pressed oils was influenced by various factors such as source of raw material, genotype, time of harvest, storage, moisture content, pre-processing, extraction method, extraction solvent, etc. Due to increased consumer awareness for healthier foods, cold pressed oils have become popular choices for consumers as they are seen as economically secure options with beneficial minor compounds and nutritional value. The results of the present investigation demonstrated that cold pressed oils contain important bioactive compounds like antioxidants and nutrients, which help in enhancing the quality and nutritional value of oils. Moreover, our study suggests that incorporating a variety of oils into one’s diet, either through rotation or blending, to fulfill daily energy needs from total fats can offer advantages over individual oils in terms of nutritional and health benefits. Further studies are needed to explore this concept and confirm its potential advantages.