Quality assessment of frying fats and fried snacks during continuous deep-fat frying at different large-scale producers

Formation of AGEs in Penaeus vannamei fried with high oleic acid sunflower oil

Here, we investigated the effects of frying process on the formation of advanced glycation end products (AGEs) in shrimps using Penaeus vannamei as the raw material. The results showed that the oil, malondialdehyde, fluorescent AGEs, carboxymethyl lysine (CML), methylglyoxal hydroimidazolone (MG-H1) and the outer layer carboxyethyl lysine (CEL) content was higher in the fried shrimps than that in the raw unfried shrimps. The outer layer CML, CEL and inner CEL, MG-H1 values all reached the maximum after the first batch of frying (22.43 mg/kg, 304.24 mg/kg, 83.76 mg/kg, and 169.42 mg/kg respectively). However, fluorescent AGEs and MG-H1 of the outer layer reached the maximum after the fifth and fourth batches of frying (1230.0 AU/g and 341.63 mg/kg). Malondialdehyde, fluorescent AGEs, CML, MG-H1, and CEL concentration in the fried shrimps firstly increased and then decreased to stabilization with more frying batches, with higher content in the outer layer of fried shrimps.

Enhancement of Oxidative Stability of Deep-Fried Sunflower Oil by Addition of Essential Oil of Amomum villosum Lour

In this study, the essential oil of the fruits of Amomum villosum Lour. (AVEO) was extracted through steam distillation and the components of the AVEO were analyzed using Gas Chromatography-Mass Spectrometry (GC-MS). Additionally, the antioxidant capacity in vitro of the AVEO was gauged using radical scavenging activity (DPPH, ABTS, superoxide anion) and ferric ion reducing antioxidant power (FRAP) assays; the antioxidant effect of a certain concentration of AVEO is even comparable to 0.08 mg/mL of butylated hydroxytoluene (BHT). Moreover, AVEO was applied to sunflower oil in a 30 h successive deep-frying experiment. Throughout the frying procedure, the sunflower oil-added antioxidant showed different degrees of benign changes in the physical and chemical parameters compared to the blank group, with 1 g/kg of AVEO being more consistent with 0.01 g/kg of tert-butyl hydroquinone (TBHQ), while 1.5 g/kg of essential oil revealed a stronger antioxidative capability. Meanwhile, the organoleptic characteristics of Chinese Maye, including its appearance, taste, flavor, and overall acceptability, were ameliorated when AVEO was added at 1.5 g/kg. Consequently, AVEO can be applied to substitute synthetic antioxidants as a natural antioxidant and flavoring agent during the deep-frying course of food.

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.

Study on the physicochemical and flavor characteristics of air frying and deep frying shrimp (crayfish) meat

This study aimed to compare the changes in the quality characteristics of air-fried (AF) shrimp meat and deep-fried (DF) shrimp meat at different frying temperatures (160, 170, 180, 190°C). Results showed that compared with DF, the moisture and fat content of air-fried shrimp meat (AFSM) was lower, while the protein content was higher. At the same frying temperature, the fat content of the AFSM was 4.26-6.58 g/100 g lower than that of the deep-fried shrimp meat (DFSM). The smell of the AFSM and DFSM was significantly different from that of the control group. The results of the electronic tongue showed that each of the two frying methods had its flavor profile. Gas chromatography-ion mobility spectrometry (GC-IMS) identified 48 compounds, and the content of volatile compounds detected in AFSM was lower than that in DFSM. Among them, the highest level of volatile compound content was found in the DF-190. E-2-pentenal, 2-heptenal (E), and methyl 2-methyl butanoate were identified only in DFSM. In addition, a total of 16 free amino acids (FAAs) were detected in shrimp meat. As judged by sensory evaluation, the AFSM at 170°C was the most popular among consumers.

Deep-frying oil induces cytotoxicity, inflammation and apoptosis on intestinal epithelial cells

BACKGROUND

Deep-frying oil has been found to cause inflammatory bowel disease (IBD). However, the molecular mechanism of the effect of deep-frying palm oil on IBD still remains undetermined.

RESULTS

In the present study, bioinformatics and cell biology were used to investigate the functions and signal pathway enrichments of differentially expressed genes. The bioinformatics analysis of three original microarray datasets (GSE73661, GSE75214 and GSE126124) in the NCBI-Gene Expression Omnibus database showed 17 down-regulated genes (logFC < 0) and 2 up-regulated genes (logFC > 0) existed in the enteritis tissue. Meanwhile, pathway enrichment and protein-protein interaction network analysis suggested that IBD is relevant to cytotoxicity, inflammation and apoptosis. Furthermore, Caco-2 cells were treated with the main oxidation products of deep-frying oil-total polar compounds (TPC) and its components (polymerized triglyceride, oxidized triglycerides and triglyceride degradation products) isolated from deep-frying oil. The flow cytometry experiment revealed that TPC and its components could induce apoptosis, especially for oxidized triglyceride. A quantitative polymerase chain reaction analysis demonstrated that TPC and its component could induce Caco-2 cell apoptosis through AQP8/CXCL1/TNIP3/IL-1.

CONCLUSION

The present study provides fundamental knowledge for understanding the effects of deep-frying oils on the cytotoxic and inflammatory of Caco-2 cells, in addition to clarifying the molecular function mechanism of deep-frying oil in IBD. © 2021 Society of Chemical Industry.

Monitoring of frying process in canola oil blend using fourier transform infrared and chemometrics techniques

The production of trans-fats and chemical changes during the process of frying are serious public health concerns and must be monitored efficiently. For this purpose, the canola oil was formulated with different ratio of extra virgin olive oil and palm olein using D-optimal mixture design, and the best formulation (67:22:11) based on free fatty acid (FFA) content, peroxide value (PV), and iodine value (IV) as responses was selected for multiple frying process. The data on FFA, PV, and IV along with Fourier transform-infrared (FT-IR) spectra were taken after each frying up to ten frying. The spectral data were preprocessed with standard normal variate followed by principal component analysis which is clearly showing the differentiation for various frying. Similarly, partial least square regression was applied to predict the FFA (0.37%-1.63%), PV (4.47-13.85 meqO2/kg), and IV (111.51-51.39 I2/100 g) which demonstrated high coefficient of determination (R2) 0.84, 0.83, and 0.81, respectively. It can be summarized that FT-IR can be used as a novel tool for fast and noninvasive quality determination of frying oils.

Molecular dynamics revealed the effect of epoxy group on triglyceride digestion

The digestion behavior of epoxy triglyceride, the main cytotoxic product of deep-frying oil, remains unknown, which may affect its biosafety. In this study, epoxy triglyceride (EGT) and triglyceride (GT) were used to reveal the effect of epoxy group on digestion. Digestibility rate analysis showed that the free fatty acids release rate of EGT was slower. To clarify this phenomenon, binding ability with salt ions in digestive juice and particle size were also been studied. Cluster size analysis indicated that epoxy group increased triglyceride particle size, resulting in smaller contact area between EGT and lipase. Interface behaviors displayed EGT decreased binding ability with salt ions in digestive juice. Spectroscopic analysis showed EGT caused the red shift of lipase peak, indicating that epoxy group changed lipase structure. Molecular dynamics simulation suggested EGT leads to loosen lipase structure. In conclusion, this study highlights that epoxy group could weaken the triglyceride digestion.

Oxidative stability of high oleic sunflower oil during deep-frying process of purple potato Purple Majesty

The behaviour of high oleic sunflower oil in deep frying process of purple potato Purple Majesty has been evaluated simulating a fast food cooking process. This oil was used for 8h/day for 6 days, filling up from the 2nd day. A discontinuous and prolonged procedure was tested. Free Fatty Acidity (FFA), Peroxide Value (PV), Total Polar Compounds (TPC), Fatty Acid (FA) composition, Volatile Organic Compounds (VOC) have been determined at different times in thermo-oxidized (T-OX) oil, and in frying oil. The FFA in T-OX oil samples showed values in the range 0.09%–0.24%, whereas in the frying oil values varied in a range between 0.09% and 0.16%. TPCs values varied from 1.76% to 38.24% in T-OX oils, whereas in frying oil used for frying purple potatoes (FOPP) showed values in the range from 1.76 to 29.13%. The peroxides values did not follow a regular pattern, both during thermo-oxidation and during frying. Among the Long Chain Fatty Acids (LCFAs), oleic acid was the most represented (84.13%). Short chain fatty acids (SCFAs) amount was 0.34% (octanoic acid). Medium chain fatty acids (MCFA) amount was 4.45% (palmitic acid). During the thermo-oxidation, the poly-unsaturated fatty acids (PUFA) amount decreased during the 48 h of heat treatment, reaching an amount of 6.21%. This determined the increase in short chain fatty acids (SCFA). Trans fatty acids increased with the frying time. Unsaturated fatty acids (UFA) reached the value of 90.19%; SFA was 9.79%, and octanoic acid was 0.20%. A correlation between TPC vs UFA/SFA and TPC vs C18:2/C16:0 was observed in the frying oil. The most abundant volatile compounds in frying oil (from 0 to 48 h) were the aldehydes produced by decomposition of hydroperoxides of oleic and linoleic acids.

A preliminary study on the quality of street vended foods around a university in Kunming, China

The street vended foods (SVF) are very popular in China, particularly in highly adolescents populated regions such as schools. Food quality is a critical global issue, but there are few studies describe the quality assessment of SVF. In this study, the quality of SVF around a university in Kunming was evaluated, including the microbial quality, proximate composition, oil quality, and heavy metal content. Microbial results showed that the aerobic plate count (APC) and Escherichia coli (E. coli) counts ranged from 1.94 to 7.43 log CFU/g or ml, and 0.53 to 1.48 log CFU/g or ml, respectively. A portion of fried snack samples exceed the standard limit of acid value (AV) and peroxide value (POV), and the same result was observed in carbonyl group value (CGV), thiobarbituric acid (TBA) value, viscosity, and conductivity. The proximate composition of the fried snack samples varied widely, while the fat content was generally higher. The heavy metal analysis showed most samples met the safety standards, with the content of 12-51, 1-19, 12-73, and 11-88 μg/kg for As, Hg, Cd, and Pb, respectively. In conclusion, although the overall results of this study were satisfying, more attention should be given to the quality of SVF. Consequently, there is a need for additional measures to protect consumers, particularly young adults in college, from foodborne disease.

Characterization of Oil Uptake and Fatty Acid Composition of Pre-treated Potato Slices Fried in Sunflower and Olive Oils

In this study, the oil uptake and fatty acid composition of fried potato slices were determined. Some pre-treatments such as blanching, freezing, and blanching-freezing were applied to potato slices before frying while the untreated samples were used as a control. The frying process was carried out in sunflower and olive oils. The percentage oil uptake in slices varied from 4.26% to 10.35% when fried in sunflower oil. In the case of the control samples slices fried in olive oil contained high monounsaturated fatty acid (oleic acid) content (5.45%), and lesser oil uptake was observed than those processed in sunflower oil, which is rich in polyunsaturated fatty acid (linoleic acid is 5.99%) (p < 0.05). The oil uptake was also compared in the case of potato slices fried in two different oils after pre-treatments. The maximum oil uptake was observed in the case of blanched-frozen potatoes, whereas minimum oil uptake was observed in frozen only slices for both oils. The fatty acid contents in oils extracted from fried potato slices showed that the predominant fatty acids were palmitic, stearic, oleic, and linoleic acids. The best results were observed in frozen potato slices fried in both sunflower and olive oils.

Can the Image Processing Technique Be Potentially Used to Evaluate Quality of Frying Oil?

The objective of this study was to investigate the feasibility of a computer vision system (CVS) for assessing the contact angle of frying oil. The oil was used to fry carbohydrate- and protein-based foods for 40 h, and the oil was collected for measuring free fatty acids (FFA), peroxide value (PV), total polar materials (TPMs), and FOS reading (dielectric constant). The results showed that FFA linearly increased with frying time (R2 > 0.95) while the polynomial correlation between TPMs and FOS reading as a result of time was observed (R2 > 0.97). The contact angle obtained from CVS was highly correlated with all chemical qualities (R2 > 0.94), except PV. In addition, the contact angle models could be used to adequately predict FFA, TPMs, and FOS reading of frying oil (R2 > 0.91). This result suggested that the image processing technique through CVS could be an appropriate alternative to chemical analysis, especially for small- and medium-scale industrial frying.

Effect of frying and storage on oxidative quality of conjugated linoleic-acid-rich soybean oil produced by photoisomerization using plantain as a model system

BACKGROUND

Conjugated linoleic acid (CLA) is known to have beneficial properties to health. Naturally, in foods it is found in very low concentrations, and so these beneficial properties cannot be obtained. This study investigated the enrichment of soybean oil by photoisomerization, as well as assessing its oxidative stability during the frying process using plantain slices as a model system and after a storage period of 20 days at 60 °C.

RESULTS

The oxidative stability of soybean oil enriched with CLA by photoirradiation was measured based on the peroxide, p-anisidine, and Totox values, as well as by the polyphenol content, tocopherol content and DPPH^· scavenging capacity. The results obtained showed that a substantial amount of CLA was obtained by photoirradiation (31.73%). The oxidative stability values of the oil enriched with CLA showed good stability during a frying cycle; however, this stability decreased when it was stored and during the final frying cycles.

CONCLUSIONS

The results obtained indicated that photoirradiation is a good technique for obtaining oils enriched with CLA, and in this way CLA can be incorporated into foods; however, it is necessary to add antioxidants to improve their stability. © 2019 Society of Chemical Industry.

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.

Frying stability of sunflower oil blended with jujube (Ziziphus mauritiana Lam.) leaf extract

The aim of present study was to compare the effects of ultrasound‐assisted and microwave‐assisted extraction with solvent extraction method on antioxidant activities of jujube (Ziziphus mauritiana Lam.) leaf extracts in stability of sunflower oil during deep frying. The antioxidant activities of the extracts were evaluated by using 2, 2‐diphenyl‐1‐picrylhydrazyl (DPPH˙) radical scavenging and β‐carotene bleaching assays. Ultrasound‐assisted extraction was the most effective method on antioxidant activities of extracts and extraction yield of phenolic compounds compared to other extraction techniques. Protective effect of methanol–water extract of jujube leaf obtained with ultrasound‐assisted extraction (ULMW) at 500 and 700 ppm in stability of sunflower oil was compared to synthetic antioxidants by measuring total polar compounds (TPC), carbonyl value (CV), peroxide value (PV), free fatty acids (FFA), oxidative stability index (OSI), conjugated dienes (CD), and trienes values (CT). Results showed ULMW at 700 ppm had higher stabilization efficiency than synthetic antioxidants.

Rapid and Sensitive Determination of Lipid Oxidation Using the Reagent Kit Based on Spectrophotometry (FOODLABfatSystem)

The reliability and availability of FOODLABfatsystem for determining acid value (AV) and peroxide value (POV) were assessed during the hydrolytic rancidification and lipid oxidation of edible oils. This reagent kit based on spectrophotometry was compared to the official methods (ISO 660 and 3960 protocols) based on manual titration employing the standard mixture for the simulated oxidation models and edible oils during the thermally induced oxidation at 180°C. The linear regression line of standard mixture and the significant difference of thermally oxidized time course study determined between them showed high correlations (R2=0.998andp<0.05) in both AVs and POVs. Considering ISO protocols with a probability of human error in manual titration, the rapidness and simplicity of the reagent kit based on spectrophotometry make it a promising alternative to monitor the lipid oxidation of edible oils and lipid-containing foods.

Changes of Major Antioxidant Compounds and Radical Scavenging Activity of Palm Oil and Rice Bran Oil during Deep-Frying

Changes in antioxidant properties and degradation of bioactives in palm oil (PO) and rice bran oil (RBO) during deep-frying were investigated. The alpha (α)-tocopherol, gamma (γ)-tocotrienol and γ-oryzanol contents of the deep-fried oils were monitored using high performance liquid chromatography, and antioxidant activity was determined using 2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging activity. Results revealed that the antioxidant activity of PO decreased significantly (p < 0.05), while that of RBO was preserved after deep-frying of fries. As expected, the concentration of α-tocopherol in PO and γ-tocotrienol in both PO and RBO decreased significantly (p < 0.05) with increased frying. Results also showed that γ-tocotrienol was found to be more susceptible to degradation compared to that of α-tocopherol in both PO and RBO. Interestingly, no significant degradation of α-tocopherol was observed in RBO. It is suggested that the presence of γ-oryzanol and γ-tocotrienol in RBO may have a protective effect on α-tocopherol during deep-frying.