Simultaneous monitoring of the conventional qualitative indicators during frying of sunflower oil

Changes in the Quality of High-Oleic Sunflower Oil during the Frying of Shrimp (Litopenaeus vannamei)

Shrimp fried in vegetable oil is a very popular food, so it is important to study the changes in the quality of the oil during frying. In order to more precisely study the nature of frying oil during the cooking process, this study investigated the quality changes of high-oleic sunflower oil during the frying of South American white shrimp (Litopenaeus vannamei). The oxidation and hydrolysis products of frying oils were investigated by integrating the proton nuclear magnetic resonance technique with traditional oil evaluation indexes in an integrated manner. The results showed that the color difference as measured using the ΔE* value increased gradually during the process. Moreover, the acid value, carbonyl value, and total oxidation significantly increased with prolonged frying time. The major oxidation products formed during frying were (E,E)-2-alkenals, (E,E)-2,4-alkadienals, and E,E-conjugated hydroperoxides. This indicated that longer treatment times corresponded with an increased accumulation of aldehydes and ketones, and an increased degree of oxidative deterioration of the oil. However, the proportion of oleic acid in the frying oil increased with the frying of shrimp, reaching 80.05% after 24 h. These results contribute to our understanding of the oxidative deterioration of high-oleic oils during frying, and provide an important reference for the application properties of high-oleic oils.

Machine Learning-based Predictive Analysis of Total Polar Compounds (TPC) content in Frying Oils: A Comprehensive Electrochemical Study of 6 Types of Frying Oils with Various Frying Timepoints

Standard approaches to determining the total polar compounds (TPC) content in frying oils such as the chromatographic techniques are slow, bulky, and expensive. This paper presents the electrochemical analysis of 6 types of frying oils inclusive of 52 frying timepoints, without sample preparation. This is achieved via impedance spectroscopy to capture sample-specific electrical polarization states. To the best of our knowledge, this is a first-of-its-kind comprehensive study of various types of frying oils, with progressively increasing frying timepoints for each type. The principal component analysis distinguishes the frying timepoints well for all oil types. TPC prediction follows, involving supervised machine learning with sample-wise leave-one-out implementation. The R² values and mean absolute errors across the test samples measure 0.93-0.97 and 0.43-1.19 respectively. This work serves as a reference for electrochemical analysis of frying oils, with the potential for portable TPC predictors for rapid accurate screening of frying oils.

Quality Change in Camellia Oil during Intermittent Frying

Camellia oil with a high oleic acid content is widely used for frying. To comprehensively describe the quality change in camellia oil during frying, the changes in composition, deterioration indicators, and volatile profiles were investigated. The results showed that tocopherols mainly degraded in the early stage of frying, followed by unsaturated fatty acids (UFA). This caused the carbonyl value and total polar compounds level to significantly increase. Moreover, frying promoted the accumulation of volatile compounds in terms of type and abundance, especially aldehydes, which are related to the degradation of UFA. Principal component analysis showed that the frying of camellia oil was divided into three stages. First, the camellia oil with a heating time of 2.5-7.5 h showed excellent quality, where tocopherol played a major role in preventing the loss of UFA and was in the degradation acceleration stage. Subsequently, as tocopherol entered the degradation deceleration stage, the quality of camellia oil heated for 10.0-15.0 h presented a transition from good to deteriorated. Finally, tocopherol entered the degradation stagnation stage, and the quality of camellia oil heated for 17.5-25.0 h gradually deteriorated, accompanied by a high level of volatile compounds and deterioration indicators. Overall, this work comprehensively determined the deterioration of camellia oil during intermittent frying and offered valuable insights for its quality evaluation.

Improving the Oxidation Stability and Shelf-Life of Peanut Oil by Addition of Rosemary Extract Combined with Vitamin C and Ascorbyl Palmitate

Rosemary extracts are natural antioxidants, which can be considered an alternative for synthetic antioxidants in the food industry. The aim of the present study was to evaluate the oxidation stability and shelf-life of rosemary extracts combined with vitamin C (VC) and ascorbyl palmitate (AP) in peanut oil stored at 65°C. Peanut oil with tertbutyl hydroquinone (TBHQ) and without additives served as positive and negative controls, respectively. The peroxide value (POV), thiobarbituric acid reactant (TBARs), conjugated diene (CD), and conjugated triene (CT) values of the peanut oil samples were evaluated during accelerated storage every 48 h. Among them, 0.23 g/kg rosemary extracts combined with 0.13 g/kg VC and 0.07 mg/kg AP exhibited the best oxidative stability. Additionally, the oxidation kinetics model predicated that the rosemary extracts combined with VC and AP could effectively prolong the shelf-life of peanut oil. In accelerated storage, the rosemary extracts combined with VC and AP not only inhibited peanut oil oxidation like chemical antioxidants, but also were safer than chemical antioxidants. Therefore, the rosemary extracts combined with VC and AP were an effective alternative to chemical antioxidants, which could improve the oxidation stability and shelf-life of peanut oil.

Effect of boiling and oven roasting on some physicochemical properties of sunflower seeds produced in Far North, Cameroon

The effects of different processing methods on proximate composition, total phenolic content, antioxidant activity, lipid oxidation, and mineral contents of sunflower seeds produced in Far North Region of Cameroon were evaluated. Mean moisture, ash, lipid, protein, fiber, and carbohydrate contents of raw sunflower seeds were 6.60%, 2.55%, 44.65%, 20.17%, 4.08%, and 21.25%, respectively. The changes in moisture, ash (excepted in boiled samples), lipid, protein, fiber, and carbohydrate (excepted in roasted samples) were found to be significant for all cooking methods. Ash and lipid contents of samples roasted at 120°C were found to be significant when compared with other cooking methods. Antioxidant activity increased with treatment. After processing, the acid, peroxide, and thiobarbituric acid values increased significantly, whereas iodine value decreased. The roasting process improved the induction time, and samples roasted at 120°C were found to have the highest induction time (2.29 ± 0.09 hr). Raw sunflower seeds were good sources of potassium (K), magnesium (Mg), calcium (Ca), iron (Fe), zinc (Zn), and manganese (Mn). Increase in contents of Ca, Mg, Zn, Cu, and Fe was observed during processing. Roasting compared with boiling appeared to be the best cooking method of sunflower seeds concerning nutrient content, antioxidant stability, and lipid stability.

Determination of the changes in sunflower oil during frying of leavened doughs using response surface methodology

In this study, the effect of dough salt content, frying temperature and time on the conjugated diene values, polymer triglyceride content, total polar material content, viscosity, and color values of the sunflower oil during frying of leavened doughs was determined using response surface methodology. Fifty repeated frying operations were applied in the same day at 160-200 °C for 1-5 min and doughs with 0-2% salt content. According to the results of the study, frying temperature, frying time and dough salt content were significantly (p < 0.05) affected total polar material content, polymer triglyceride content, viscosity and a* and b* color values of oil samples, whereas dough salt content did not affect the L* color values and conjugated diene value of oil significantly (p > 0.05). To minimize the oxidation products of frying oil, the frying process can be applied at 160 °C for 1 min using dough with 1.97% salt content.

The formation, determination and health implications of polar compounds in edible oils: Current status, challenges and perspectives

To effectively control the quality of edible oil, polar compounds in edible oils have been studied extensively in the past few decades, particularly in the field of frying. This article critically reviews the formation, determination, and health implications of the polar compounds in edible oils via comprehensive literature research. The challenges and perspectives of polar compounds in edible oils are also discussed. Three chemical reactions, including oxidation, hydrolysis, and polymerization, elaborate polar compound formation. Many techniques are used to determine the total polar compound content of edible oils, with comparative analysis; Fourier transform infrared technique is a relatively ideal method. A major obstacle for nutritional studies focused on polar compounds formed during frying is that few pure compounds have been quantified. To inhibit the formation of the polar compounds effectively, investigations into the applications of enzymatic method in developing new lipophilized antioxidants may be a new direction in research.

Quercetin Inhibited the Formation of Lipid Oxidation Products in Thermally Treated Soybean Oil by Trapping Intermediates

In this research, we studied the inhibitory mechanism of quercetin, one popular phenolic compound, against aldehyde formation in thermally treated soybean oil. It was found that quercetin reduced unsaturated aldehyde formation significantly, with the inhibitory effect decreased with the extension of the heating time. Meanwhile, quercetin had minimum effects on the fatty acid profile compared to untreated samples. Some new phenolic derivatives were formed in thermally treated soybean oil with quercetin, further analyzed by liquid chromatography-tandem mass spectrometry, and compared to newly synthesized derivatives (characterized by mass spectrometry and nuclear magnetic resonance spectroscopy). On the basis of their chemical structures, we proposed that quercetin reacted with 13-oxo-octadecadienoic acid, 10-oxo-hexadecenoic acid, and 10-oxo-octadecenoic acid formed from peroxidation of linoleic acid, palmitoleic acid, and oleic acid, respectively, to inhibit aldehyde formation. In addition, newly formed quercetin-3-O-hexanoate, quercetin-3-O-heptanoate, and quercetin-3-O-nonanoate showed weaker 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical cation scavenging activity and weaker antioxidant activity in soybean oil, which explained the decreased inhibitory activity of quercetin against aldehyde formation during heat treatment. More interesting, quercetin-3-O-hexanoate showed improved cellular antioxidant activity compared to the parent quercetin. Overall, quercetin inhibited the formation of lipid oxidation products in thermally treated soybean oil by reacting with early intermediates in the lipid oxidation reaction, and quercetin derivatives formed in the process could be with enhanced cellular antioxidant activity. Our results provide novel insight into the inhibitory mechanism of quercetin against the formation of lipid oxidation products.

Detection for Frying Times of Various Edible Oils Based on Near-Infrared Spectroscopy

Taking a variety of edible oils as the research object, including soybean oil, peanut oil, rapeseed oil, a method based on Near-Infrared Spectroscopy (NIRS) to identify the frying times is proposed to evaluate the quality of frying oil. Ten rounds of frying experiments are carried out for each of the three oils. The spectra of the first eight rounds are used to build the model, and the last two are used for model testing. First, all the original spectra are preprocessed using the first derivative (1D). Then, the correlation coefficient between the sequence of frying times and absorbance is calculated, and the characteristic wavelengths with a high correlation coefficient are extracted. Finally, a differential prediction model is established based on the characteristic wavelengths. The results show that the differential prediction model accurately predicts the frying times of various edible oils and provides a new method for quality inspection of frying oil, and the predicted accuracy of the frying times of three frying oils is 100% within the allowable range of error.

Antioxidant Effects of Green Tea Leaf Extract on Chemical properties of Corn Refined Oil of Microwave Fried Potatoes

Introduction: Oxygen, light, heat, metal ions, and enzymes are among the agents that oxidize oils, fats, and high-fat food products which result in oxidative spoilage. Due to the toxicity and cancer risk of oxidative agents, the use of synthetic antioxidants is important for delaying the oxidation processes. The purpose of this study was to evaluate the protective effect of natural antioxidants including green tea leaf extract and butylated hydroxytoluene (BHT) on the oxidation of the corn refined oil of microwave-heated fried potatoes. Methods: To this end, corn refined oil and corn oil were treated with green tea leaf extracts (i.e., 200, 400, 600, and 800 ppm), followed by treating the oils with a combination of green tea leaf extract (600 ppm) and BHT (200 ppm). The samples with no anti-oxidant treatments were used as the controls. Eventually, several parameters related to the corn oils were determined, including peroxide content, acidity, polar compounds, and ionic bond conjugates. Results: Based on the results, significant increases were observed in peroxide, acidity, polar compounds, and ionic bond conjugates in the corn refined oil of microwave fried potatoes (P<0.05). On the other hand, the results showed that the heating process reduced peroxide content (P<0.05). However, acidity increased significantly during the heating process (P>0.05) and the lowest acid value was observed in the mixture of 600 ppm of the green tea leaf with 200 ppm of the BHT. There was no significant difference between the control group and the samples treated with 200 ppm of the green leaf extract (P<0.05) in terms of polar components. In addition, a significant decrease was found in the conjugated dienes by increasing the green tea leaf extract concentration (P<0.05). Finally, the highest protection was achieved in the oils that were treated with a combination of green tea leaf extract and BHT. Conclusion: In general, the green tea leaf extract and BHT have antioxidant activities that make them suitable agents for use in food protection industries.

Investigation on the quality diversity and quality-FTIR characteristic relationship of sunflower seed oils

Forty-one sunflower seed oil (SSO) products were collected to investigate their quality parameters before and after high-temperature and short-time (HTST) cooking, including peroxide value (PV), acid value (AV) and fatty acid (FA) composition. Their Fourier-transform infrared (FTIR) spectra were then scanned to explore the parameter-FTIR characteristic relationship using chemometrics with multiple linear regression (MLR) analysis. The PV and AV of uncooked products were in the range of 1.49-6.29 mmol kg-1 and 0.04-0.31 mg g-1, with the variation coefficient of 36.47% and 146.82%, respectively. They were mainly composed of palmitic acid (2.39-3.33%), stearic acid (1.76-2.54%), oleic acid (10.02-24.77%) and linoleic acid (66.42-83.62%). The parameter changes caused by HTST cooking were slight. SSO products from different countries might have significantly different FA composition, especially linoleic acid content (P < 0.05), and those with different shelf times might differ in PV (P < 0.05). In addition, the FTIR spectra of cooked and uncooked SSO showed the similarity degree values ranging from 0.67 to 0.97 and 0.72 to 0.97, respectively. All the spectra exhibited the characteristic bands of -C-H, -C[double bond, length as m-dash]O, -C-O- and [double bond, length as m-dash]CH2, in which 11 common bands as independent variables were selected to establish various FTIR characteristic-quality relationship models. The models of palmitic acid, oleic acid and linoleic acid were acceptable for their content predictions. Moreover, the cooked oils and uncooked oils could be completely distinguished by orthogonal partial least squares discriminant analysis due to the cooking-caused changes in FTIR spectrum. Production place and shelf time were the important factors related to the quality diversity of SSO, and FTIR spectroscopy combined with chemometrics was feasible for the simultaneous determination of various quality parameters.

Rapid Assessment of Deep Frying Oil Quality as Well as Water and Fat Contents in French Fries by Low-Field Nuclear Magnetic Resonance

Most of the health hazards in fried foods are related to unqualified frying oil and excessive oil content. In this study, the feasibility of using low-field nuclear magnetic resonance techniques (LF-NMR) for analysis of the water and oil contents in French fries, as well as simultaneous evaluation of frying oil quality during deep frying, was investigated. Three proton populations were identified and successfully assigned to water and oil relaxation signals. Significant correlation between the T₂ relaxation parameters ( A_water and RC_oil) and the water and oil content was acquired. MRI could visualize the changes of signal intensity and spatial distribution, as well as the internal structural changes during frying. Using the correlation model built by multiple regression analysis, the total polar compounds content of the frying oil could be successfully predicted by LF-NMR relaxation characteristics, which indicates that LF-NMR was an effective method to monitor the quality of frying oil.

Evolution of Frying Oil Quality Using Fourier Transform Near-Infrared (FT-NIR) Spectroscopy

This study assesses the capacity of a Fourier transform near-infrared (FT-NIR) spectrometer operating in the range 4500-12 000 cm^-1 (833.33-2222.22 nm) to provide quantitative predictions for the parameters of acidity (AV), p-anisidine (pAV), total polar materials (TPM), peroxide value (PV), and oxidative stability index (OSI). 562 samples of frying oil were analyzed from 14 distinct types of oil. The calibrations obtained accounted for 96%, 95%, 99%, 92%, and 91% of the AV, pAV, TPM, PV, and OSI variations in the study set and the similarity between the standard error of laboratory (RMSEP) values and the reference method errors (RMSEL), enabling the authors to conclude that NIR technology has the capacity to replace traditional methods in thermo-oxidative degradation studies in frying oils.

Electronic nose guided determination of frying disposal time of sunflower oil using fuzzy logic analysis

An electronic nose (e-nose), having 18 metal oxide semiconductor (MOS) sensors, guided determination of frying disposal time of sunflower oil is reported. The ranking and screening of MOS sensors, specific for volatile organic compounds, was performed using fuzzy logic. A correlation was examined between rancidity indices of fried oil (total polar compounds (TPC), and triglyceride dimers-polymers (TGDP), among others) and e-nose based odor index. Fuzzy logic screened 6 MOS sensors (LY2/G, LY2/AA, LY2/GH, LY2/gCT1, T30/1, and P30/1) to deconvolute the rancid fried oils using hierarchical clustering on principal component space. A good relationship was noted between rancidity indices and odor index (R²>0.85). Based on maximum discard limits of rancidity indices (25% TPC and 10% TGDP), the frying disposal time of 15.2h (TPC) vs. 15.8h (e-nose) and 15.5h (TGDP) vs. 16.3h (e-nose) was determined. The demonstrated methodology holds a potential extension to different fried oils and products.

Evaluation of antioxidant activity of loquat fruit (Eriobotrya japonica lindl.) skin and the feasibility of their application to improve the oxidative stability of soybean oil

The effects of ultrasound-assisted, supercritical CO2 and solvent extraction techniques on antioxidant activity of loqua (Eriobotrya japonica Lindl.) skin extract in oxidation stability of soybean oil was evaluated. The antioxidant efficacy of extracts was determined using 2, 2-diphenyl-1-picrylhydrazyl (DPPH(•)) radical scavenging capacity, β-carotene/linoleic acid, and Rancimat test system. Results showed that solvent extract of loquat fruit skin at 400 ppm had the highest antioxidant activity compared to ultrasound-assisted and supercritical CO2 extracts. Further, solvent extraction was the most effective method for extraction of phenolic compounds. Protective effects of extracts in stabilization of soybean oil during both frying and storage conditions were tested and compared to tert-butyl hydroquinone (TBHQ) by measuring their peroxide value, free fatty acids, conjugated dienes and trienes value. During frying process solvent extract of skin at 400 ppm (SOEA) exhibited stronger antioxidant activity in oil compared to other oil samples, but this antioxidant potential was lower than TBHQ in storage conditions. Present study showed that loquat fruit skin is a good source of natural antioxidant compounds, and has the potential to be used as a substitute for synthetic antioxidants in vegetable oils.

Stability of Silica- and Enzyme-Treated Palm Oil Under Deep Frying Conditions

The oxidative and thermal stability of low diglycerides palm oil produced via silica treatment (sPO) and enzymatic treatment (ePO) compared with standard quality palm oil (SQ) and premium quality palm oil (PQ) was investigated. Both of the oils displayed better oxidative stability compared with SQ as well as significantly higher (P < 0.05) thermal resistance and oxidative strength than SQ and PQ due to lower amounts of partial glycerides. Although the initial induction periods (IPs) of sPO and ePO were significantly lower compared with SQ and PQ, both the oils showed slower drops in their IP values. The darkening effect after frying was significantly (P < 0.05) slower in sPO compared with SQ, PQ, and ePO. Besides, there is no difference p > 0.05 in the rate of FFA formation between sPO and PQ. The anisidine value and peroxide values were lowest in sPO, followed by ePO, PQ, and SQ.

A simplified FTIR chemometric method for simultaneous determination of four oxidation parameters of frying canola oil

Transmission Fourier transform infrared (FTIR) spectroscopic method using 100 μm KCl cell was applied for the determination of total polar compounds (TPC), carbonyl value (CV), conjugated diene (CD) and conjugated triene (CT) in canola oil (CLO) during potato chips frying at 180 °C. The calibration models were developed for TPC, CV, CD and CT using partial least square (PLS) chemometric technique. Excellent regression coefficients (R(2)) and root mean square error of prediction values for TPC, CV, CD and CT were found to be 0.999, 0.992, 0.998 and 0.999 and 0.809, 0.690, 1.26 and 0.735, respectively. The developed calibration models were applied on samples of canola oil drawn during potato chips frying process. A linear relationship was obtained between CD and TPC with a good correlation of coefficient (R(2)=0.9816). Results of the study clearly indicated that transmission FTIR-PLS method could be used for quick and precise evaluation of oxidative changes during the frying process without using any organic solvent.

Influence of extraction techniques on antioxidant properties and bioactive compounds of loquat fruit (Eriobotrya japonica Lindl.) skin and pulp extracts

In this study, the bioactive compounds of loquat fruit (Eriobotrya japonica Lindl.) skin and pulp extracted by two extraction methods (solvent and ultrasound-assisted) with three solvents (ethanol, water and ethanol-water) were compared to supercritical fluid extraction. The antioxidant activities of skin and pulp extracts were evaluated and compared to tertiary butylhydroquinone (TBHQ) using 2, 2-diphenyl-1-picrylhydrazyl (DPPH˙) radical scavenging, β-carotene bleaching, and the Rancimat assays. In DPPH assay solvent extracts of skin by ethanol (SSE) and ethanol-water (SSEW) showed strong inhibitory activity. The SSEW also showed the highest inhibition percentage of 85.58% by the β-carotene bleaching assay and longest induction time of 4.78 h by the Rancimat method. The large amount of tocopherols and phenolics contained in the skin extract may cause its strong antioxidant ability. The results indicated that the solvent extraction with ethanol-water produced the maximum extraction yield of phenolic and tocopherol compounds from loquat fruit skin and pulp. Furthermore, solvent extraction was the most effective in antioxidant activity of the extracts compared to other extraction techniques.

Antioxidant activity of raspberry (Rubus fruticosus) leaves extract and its effect on oxidative stability of sunflower oil

Efficacy of R. fruticosus leaves extract in stabilizing sunflower oil during accelerated storage has been studied. Extracts of R. fruticosus were prepared in different solvents which methanolic extract yield with 15.43 % was higher than water and acetone ones (11.87 and 6.62 %, respectively). Methanolic extract was chosen to evaluate its thermal stability at 70 °C in sunflower oil, due to the highest yield, antioxidant and antiradical potential and also high content of phenolic compounds campared to other solvents. So, different concentrations of methanolic extract (200, 400, 600, 800 and 1,000 ppm) were added to sunflower oil. BHA and BHT at 200 ppm served as standards besides the control. Peroxide value (PV) and thiobarbituric acid (TBA) were taken as parameters for evaluation of effectiveness of R. fruticosus leaves extract in stabilization of sunflower oil. Moreover, antioxidant activity index (AAI) of the extract at 120 °C at rancimat were conducted. Results from different parameters were in agreement with each other, suggesting the highest efficiency of 1,000 ppm of the extract followed by BHT, BHA and other concentrations of the extract. Results reveal the R. fruticosus leaves extract to be a potent antioxidant for stabilization of sunflower oil.