Volatile compound profiling from soybean oil in the heating process

Formation of lipid-derived volatile products through lipoxygenase (LOX)- and hydroperoxide lyase (HPL)- mediated pathway in oat, barley and soy bean

The aim of this study was to explore the formation of volatile lipid oxidation products by the lipoxygenase (LOX)-hydroperoxide lyase (HPL)-mediated pathway in oat, barley and soy bean. LOX activity was found only in barley and soy bean samples, but the lipase and HPL activity was detected in all samples. HPL showed particularly high activity with 13-hydroperoxides, while the activity was quite low when using 9-hydroperoxides, especially in the oat and barley. The optimum pH for HPL in different samples was similar, i.e., pH 6-7. In this condition, the volatile compounds formed dramatically with aldehydes and furans as the dominant products. Furthermore, a remarkable enzymatic degradation of lipids occurred during the preparation of food models with highly refined rapeseed oil (RO) and rapeseed oil fatty acid (ROFA) emulsions, where the ROFAs were more prone to oxidation than RO. This study shows the significance of lipid-degrading enzymes in plant-food flavour formation.

Contribution of lipid to the formation of characteristic volatile flavor of peanut oil

Lipid is an important precursor for volatile flavor formation, but it is not clear how to study the reactions involved in forming key volatile flavor compounds in peanut oil. In this paper, we innovatively established a flavor research model to investigate the contribution of different chemical reactions to the aroma compounds of peanut oil. The results showed that lipid participation in thermal reactions is necessary for forming major aroma compounds in hot-pressed peanut oil. Compared to the Maillard reaction, the lipid oxidation-Maillard reaction produces more compounds with 46 volatile substances identified. During the heating process, six new key substances were formed and the level of unsaturated fatty acids decreased by 7.28%. Among them, linoleic acid may be an important precursor for the formation of aroma components of hot-pressed peanut oil. Our study could provide theoretical guidance for understanding the volatile flavor mechanism of peanut oil and improving volatile flavor.

Bioactivity and volatile compound evaluation in sheep milk processed by ohmic heating

Ohmic heating may improve bioactive compounds and processing, ensuring food safety of beverages, liquid and pasty food, or liquid with solid pieces. Due to those traits, this study conducted a comparison between ohmic heating technology and conventional heating (CH), with a focus on assessing the impact of both methods on functional compounds (such as angiotensin-converting enzyme inhibition, α-amylase and α-glucosidase inhibition, and antioxidant activity) in both fresh and thawed raw sheep milk, which had been frozen for up to 3 mo. Different ohmic heating conditions were applied and compared to CH (3.33-8.33 V/cm vs. CH [73°C/15 s]). A total of 18 peptides with some functional activities were identified by MALDI-TOF mass spectrometry analysis. Ohmic heating samples presented the highest activities related to health, followed by CH and raw milk samples; antioxidant activity range was from 0.11% to 0.71%, antihypertensive activity ranged from 0.20% to 0.72%, and antidiabetic activity ranged from 0.21% to 0.79%. Of 51 volatile compounds detected, some were degraded by freezing, storing, and heating the sheep milk. This study showed for the first time that ohmic heating processing improved sheep milk bioactive peptides and preserved volatile compounds.

Density functional theory studies on the oleic acid thermal oxidation into volatile compounds

Oleic acid oxidation is one of the main sources of food flavor compounds. Volatile profiling was investigated using thermal desorption cryo-trapping combined with gas chromatography-mass spectrometry to analyze the volatile composition of oleic acid oxidation. A total of 43 volatile compounds, including aldehydes (11), ketones (2), alcohols (5), furans (2), acids (8), ester (12) and alkane (3) were identified from oleic acid during heating. Then, density functional theory (DFT) was applied to analyze the oxidative mechanism of oleic acid during heating. A total of 30 reactions were obtained and grouped into the peroxide (ROOH), alkoxy radical (RO•), and peroxide radical (ROO•) pathways. The structures of intermediates, transition states (TS), and products in each reaction were also determined. Results show that the branch chemical reactions were the key reactions in different reaction pathway. Moreover, the reaction priority of the thermal oxidation reaction of oleic acid was the peroxide radical mechanism > the peroxide mechanism > the alkoxy radical mechanism.

Effects of quercetin on emissions of aldehydes from heated docosahexaenoic acid (DHA)-fortified soybean oil

Home cooking has been considered as an indoor pollution problem since cooking oil fumes contain various toxic chemicals such as aldehydes. Fortifying edible oils with docosahexaenoic acid (DHA) has been applied to enhance the nutritional value of oils. This study designed a frying simulation system and examined the effect of oil type, DHA fortification, heating time, and addition of natural antioxidant on the emissions of aldehydes from heated oils. Results showed that linseed oil had the highest total aldehyde emissions, followed by soybean oil, peanut oil, and palm oil. Fortifying soybean oil with DHA increased the toxic aldehydes emitted. Quercetin, a flavonoid, significantly reduced aldehydes emitted from DHA-fortified soybean oil (by up to 39.80%) to levels similar to those of normal soybean oil. Further analysis showed that DHA-fortified soybean oil with quercetin had a significantly higher DHA and unsaturated fatty acids (UFAs) content than the control oil at each heating time point. The result indicated that quercetin inhibited emissions of aldehydes, at least in part, by protecting UFAs from oxidation. Collectively, quercetin could be used as a natural additive in DHA-fortified and normal cooking oils to reduce aldehyde emissions, indoor air pollution, and preserve functional DHA and other UFAs.

Investigations on color and flavor formed by roasting sesame polysaccharide-protein mixtures

Roasting is an important operation to produce attractive colors and distinctive flavors during the production of sesame oil. To investigate the contributions of macromolecules to the color and flavor during roasting sesame seeds, water-soluble polysaccharides (WSP) and chelator-soluble polysaccharides (CSP) sequentially extracted from sesame hull were mixed with sesame protein isolate (SPI) at different ratios (1:1, 1:2, and 2:1, w/w), then the mixtures were roasted at 180 °C for 35 min. Results showed that WSP, CSP, and SPI degraded approximately at 150 °C and SPI had the highest thermal stability. According to monosaccharide/amino acid analysis, glucose and galacturonic acid showed the highest reduction rates, as well as lysine and arginine. CSP + SPI mixtures showed greater reactivity than WSP + SPI mixtures, resulting in a darker color and many more Maillard reaction products. The predominant volatiles of roasted WSP/CSP + SPI mixtures were aldehydes and heterocyclic compounds identified by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME/GC-MS). This work provides some new information about flavor and color development during roasting sesame seeds.

Thermomechanical Autovaporization (MFA) as a Deodorization Process of Palm Oil

Throughout the vegetable oil industry, there is a focus on eradicating the volatile molecules affecting the aroma or taste of the crude oil, whether it is natural or derived from the extraction process. Refining aims to reduce these compounds to a level acceptable to the consumer. In addition, the famous conventional operation of deodorization calls for high levels of temperature depending on the boiling point used to remove the atmospheric pressure of each molecule. The process implies a vacuum level between 10 to 80 kPa absolute pressure, a temperature generally between 190 and 240 °C, and a duration of 2 to 3 h. These conditions necessarily (inevitably) lead to a decrease in the quality of refined oil. Recently, the application of the Multi-Flash Autovaporization "MFA" operation has shown the possibility of eradicating volatile molecules while adopting relatively low temperature and time levels. Despite the high boiling temperature of the volatile organic compounds (VOC), MFA leads to good efficiency in reducing VOCs and preserving oil quality. The main odorant compounds in the crude palm oil were E-2-Hexenal, heptanal, octanal, nonanal, and decanal. Specific literature can indicate precise boiling temperatures under atmospheric pressure. In addition, many experimental studies have explained the evolution of each molecule and shown how they depend on the operating parameters (inlet oil pressure from 200 to 450 kPa and from 5 and 30 s time of each cycle, and the number of cycles up to 7), and how the empirical mathematical models describe the MFA deodorization, estimate the efficiency of the whole process, and optimize the operating parameters. In this research, the thermodynamic data of absolute pressure volatility versus temperature was used to better identify the removal rate (up to around 87%) implied by an abrupt pressure drop to a vacuum of 5 kPa for p = 450 kPa, t = 25 s/cycle, and the number of cycles (C = 6). The safeguarding of the fatty acid profile illustrated the maintenance of the oil quality.

Role of Lipids in Food Flavor Generation

Lipids in food are a source of essential fatty acids and also play a crucial role in flavor and off-flavor development. Lipids contribute to food flavor generation due to their degradation to volatile compounds during food processing, heating/cooking, and storage and/or interactions with other constituents developed from the Maillard reaction and Strecker degradation, among others. The degradation of lipids mainly occurs via autoxidation, photooxidation, and enzymatic oxidation, which produce a myriad of volatile compounds. The oxidation of unsaturated fatty acids generates hydroperoxides that then further break down to odor-active volatile secondary lipid oxidation products including aldehydes, alcohols, and ketones. In this contribution, a summary of the most relevant and recent findings on the production of volatile compounds from lipid degradation and Maillard reactions and their interaction has been compiled and discussed. In particular, the effects of processing such as cooking, drying, and fermentation as well as the storage of lipid-based foods on flavor generation are briefly discussed.

Maternal oxidized soybean oil exposure in rats during lactation damages offspring kidneys via Nrf2/HO-1 and NF-κB signaling pathway

BACKGROUND

Cooking oil is an indispensable component of the human diet. However, oils usually undergo thermal oxidation. Oxidized soybean oil (OSO) has been shown to have detrimental effects on humans and has emerged as a root cause of many chronic diseases. The objective of this work was to evaluate the effects of puerpera exposure to OSO on kidney damage in the mother and offspring using lactating rats as an experimental model.

RESULTS

Pathological sections and ultrastructure showed that OSO exposure resulted in various levels of damage to lactating rats and their offspring. OSO induced oxidative stress in the kidneys of lactating rats, as evidenced by increased levels of hydrogen peroxide, interleukin (IL)-1β, and IL-8. OSO increased the activities of glutathione peroxidase and superoxide dismutase. OSO upregulated the expression of apoptosis-related genes, nuclear factor-erythroid 2-related factor 2 (Nrf2), and nuclear factor κB-related inflammatory factor genes. In the offspring of the OSO-exposed mothers, hydrogen peroxide, malondialdehyde, IL-6, and tumor necrosis factor-alpha contents were increased. Furthermore, OSO enhanced the levels of Nrf2, NAD(P)H quinone oxidoreductase 1, heme oxygenase 1, and p65 and decreased B-cell lymphoma 2.

CONCLUSION

These findings indicated that the kidneys of two generations of rats were compromised by oxidative damage when fed OSO during lactation. This study provides evidence for increasing the genes expression of the Nrf2/heme oxygenase 1 pathway to alleviate the kidney damage caused by OSO in the mother and offspring. © 2021 Society of Chemical Industry.

Optimization of Flash Extraction of Akebia trifoliata Seed Oil by the Box-Behnken Response Surface Methodology and Comparison of Oil Yields from Different Origins

The aim was to optimize the extraction process of Akebia trifoliata seed oil. Using Akebia trifoliata seed as raw material, the oil extraction rate was used as index. The effect of flash extraction on the yield of Akebia trifoliata seed oil was investigated. Taking the liquid-material ratio, extraction voltage, and extraction time as the investigation factors and the oil extraction rate of Akebia trifoliata seed as the response value and on the basis of the single-factor test, the extraction process of Akebia trifoliata seed oil was optimized by the Box-Behnken response surface method. The oil yields of Akebia trifoliata seeds from different origins in China were compared. The experimental results showed that the optimum technological conditions for flash extraction of Akebia trifoliata seed oil were as follows: liquid-material ratio, 12 : 1; extraction voltage, 150 V; extraction time, 90 s; and oil yield of Akebia trifoliata seed, 19.83%. For comparison, it is found that the oil yield of Akebia trifoliata seed produced in Qujing of Yunnan is relatively the highest, followed by Tongren of Guizhou and Zhangjiajie of Hunan; the oil yield of Akebia trifoliata seed produced in Shimian of Sichuan is the lowest. The flash extraction process of Akebia trifoliata seed oil is reasonable, and the oil yield of Akebia trifoliata seed produced in Qujing of Yunnan, China, is relatively the highest. It provides a theoretical and experimental reference for the research and development of Akebia trifoliata seed oil.

Study on the antioxidative mechanism of tocopherol loaded ethyl cellulose particles in thermal-oxidized soybean oil

Our previous study proposed preparation method of tocopherol (Toc) loaded ethyl cellulose (EC) particles as antioxidant due to instability of Toc under high temperature. The present study aimed to explore the antioxidant mechanism of loaded particles. Results showed that loaded particles prepared by EC of different viscosities (EC9, EC70, EC200) had antioxidative effect, and the antioxidant activity increased with EC viscosity. Fourier transform infrared analysis demonstrated that the interaction between EC and tocopherol was mainly hydrogen bond. Loaded particles retained effectively the thermal degradation of Toc and thus enhanced the antioxidant activity. Further investigation into thermal oxidation of EC inferred the possible antioxidative mechanism included two aspects. One was that Toc was fixed in the network structure of loaded particles formed by EC to provide a barrier for avoiding degradation. Another was that EC and Toc acted on different stages of lipid oxidation, playing the antioxidative effect together.