Oxidation Of Unsaturated Fatty Acids Research Articles

Disruption of Cell Membranes and Redox Homeostasis as an Antibacterial Mechanism of Dielectric Barrier Discharge Plasma against Fusarium oxysporum.

Direct barrier discharge (DBD) plasma is a potential antibacterial strategy for controlling Fusarium oxysporum (F. oxysporum) in the food industry. The aim of this study was to investigate the inhibitory effect and mechanism of action of DBD plasma on F. oxysporum. The result of the antibacterial effect curve shows that DBD plasma has a good inactivation effect on F. oxysporum. The DBD plasma treatment severely disrupted the cell membrane structure and resulted in the leakage of intracellular components. In addition, flow cytometry was used to observe intracellular reactive oxygen species (ROS) levels and mitochondrial membrane potential, and it was found that, after plasma treatment, intracellular ROS accumulation and mitochondrial damage were accompanied by a decrease in antioxidant enzyme activity. The results of free fatty acid metabolism indicate that the saturated fatty acid content increased and unsaturated fatty acid content decreased. Overall, the DBD plasma treatment led to the oxidation of unsaturated fatty acids, which altered the cell membrane fatty acid content, thereby inducing cell membrane damage. Meanwhile, DBD plasma-induced ROS penetrated the cell membrane and accumulated intracellularly, leading to the collapse of the antioxidant system and ultimately causing cell death. This study reveals the bactericidal effect and mechanism of the DBD treatment on F. oxysporum, which provides a possible strategy for the control of F. oxysporum.

Comparison of sea buckthorn fruit oil nanoemulsions stabilized by protein-polysaccharide conjugates prepared using β-glucan from various sources

To understand the influence of β-glucans structure on the emulsifying properties of protein-polysaccharide conjugates, sodium caseinate (NaCas) was utilized to form glycosylation conjugates with varying degrees of glycosylation (10.68–17.50%) using three β-glucans from bacteria, yeast, and oats. This process induced alterations in the secondary structure of protein. The nanoemulsions prepared with the glycosylated conjugates exhibited superior stability compared to those formulated solely with NaCas, particularly under conditions of drastic pH fluctuations and extended storage periods. The nanoemulsion prepared with the NaCas-Salecan conjugate demonstrated exceptional stability at pH 4 and 6, or storage for 20 days. Additionally, it significantly attenuated the oxidation of unsaturated fatty acids and exhibited the lowest levels of aggregation, flocculation, and free fatty acid release rate during in vitro digestion. This study suggested the potential of the NaCas-Salecan conjugates in enhancing the stability of nanoemulsions and facilitating the colorectal-targeted delivery of sea buckthorn fruit oil.

Prevention of the Quality Degradation of Antarctic Krill (Euphausia superba) Meal through Two-Stage Drying.

To achieve a krill meal of high quality, a two-stage drying involving hot-air drying and vacuum drying was investigated. Five experimental groups were established according to the different drying conditions in the second stage, including 95 °C and 101 kPa, 95 °C and 60 kPa, 75 °C and 101 kPa, 75 °C and 60 kPa, and 75 °C and 20 kPa. The results showed that reducing the drying temperature and vacuum pressure in the second stage had a significant impact on the drying characteristics, sensory quality, and bioactive compounds of krill meal. Among all five groups, the drying condition of 75 °C and 60 kPa maintained a high drying rate while preserving a phospholipid content of 30.01 mg/kg and an astaxanthin content of 37.41 mg/kg. It also effectively reduced the isomerization of astaxanthin and the oxidation of unsaturated fatty acids. These results suggested that the two-stage drying method may contribute to the production of high-quality krill meal.

Antioxidant Activity and Tyrosinase Inhibitor of Red Betel Leaf Extract

Red betel leaf (Piper Crocatum) contains flavonoids, tannins, steroids, and alkaloids, known to act as antioxidants. This study aimed to determine the antioxidant activity of red betel leaf extract. The solvents used for the extraction process are ethanol and n-hexane. The thiobarbituric acid (TBA) method was used to determine antioxidant activity. The results showed that the extract of 200 ppm inhibited fatty acid oxidation by 52.13%. No significant difference (α = 0.05) inhibition of unsaturated fatty acids oxidation between the sample and α-tocopherol at 200 ppm. The ethanol extract of red betel can inhibit the tyrosinase enzyme higher than the n-hexane extract of red betel, as seen from the IC50 value of the ethanol extract of red betel of 1655 ppm, while the IC50 value of n-hexane of red betel is 3090.56 ppm.

A Novel Strategy for the Demulsification of Peanut Oil Body by Caproic Acid.

The aqueous enzymatic method is a form of green oil extraction technology with limited industrial application, owing to the need for the demulsification of the oil body intermediate product. Existing demulsification methods have problems, including low demulsification rates and high costs, such that new methods are needed. The free fatty acids produced by lipid hydrolysis can affect the stability of peanut oil body (POB) at a certain concentration. After screening even-carbon fatty acids with carbon chain lengths below ten, caproic acid was selected for the demulsification of POB using response surface methodology and a Box-Behnken design. Under the optimal conditions (caproic acid concentration, 0.22%; solid-to-liquid ratio, 1:4.7 (w/v); time, 61 min; and temperature, 79 °C), a demulsification rate of 97.87% was achieved. Caproic acid not only adjusted the reaction system pH to cause the aggregation of the POB interfacial proteins, but also decreased the interfacial tension and viscoelasticity of the interfacial film with an increasing caproic acid concentration to realize POB demulsification. Compared to pressed oil and soxhlet-extracted oil, the acid value and peroxide value of the caproic acid demulsified oil were increased, while the unsaturated fatty acid content and oxidation induction time were decreased. However, the tocopherol and tocotrienol contents were higher than those of the soxhlet-extracted oil. This study provides a new method for the demulsification of POB.

Ferroptosis-Like Death in Microorganisms: A Novel Programmed Cell Death Following Lipid Peroxidation.

Ferroptosis is a new kind of programmed cell death of which occurrence in microorganisms is not clearly verified. The elevated level of reactive oxygen species (ROS) influences cellular metabolisms through highly reactive hydroxyl radical formation under the iron-dependent Fenton reaction. Iron contributes to ROS production and acts as a cofactor for lipoxygenase to catalyze poly unsaturated fatty acid (PUFA) oxidation, exerting oxidative damage in cells. While ferroptosis is known to take place only in mammalian cells, recent studies discovered the possible ferroptosis-like death in few specific microorganisms. Capacity of integrating PUFA into intracellular membrane phospholipid has been considered as a key factor in bacterial or fungal ferroptosis-like death. Vibrio species in bacteria and Saccharomyces cerevisiae in fungi exhibited certain characteristics. Therefore, this review focus on introducing the occurrence of ferroptosis-like death in microorganisms and investigating the mode of action underlying the cells based on contribution of lipid peroxidation and iron-dependent reaction.

Simultaneous Preparation of Chitin and Flavor Protein Hydrolysates from the By-Products of Shrimp Processing by One-Step Fermentation with Lactobacillus fermuntum.

One-step fermentation, inoculated with Lactobacillus fermentum (L. fermentum) in shrimp by-products, was carried out to obtain chitin and flavor protein hydrolysates at the same time. The fermentation conditions were optimized using response surface methodology, resulting in chitin with a demineralization rate of 89.48%, a deproteinization rate of 85.11%, and a chitin yield of 16.3%. The surface of chitin after fermentation was shown to be not dense, and there were a lot of pores. According to Fourier transform infrared spectroscopy and X-ray diffraction patterns, the fermented chitin belonged to α-chitin. More than 60 volatiles were identified from the fermentation broth after chitin extraction using gas chromatography-ion transfer spectrometry analysis. L. fermentum fermentation decreased the intensities of volatile compounds related to unsaturated fatty acid oxidation or amino acid deamination. By contrast, much more pleasant flavors related to fruity and roasted aroma were all enhanced in the fermentation broth. Our results suggest an efficient one-step fermentation technique to recover chitin and to increase aroma and flavor constituents from shrimp by-products.

Formation of free radicals in Chi-aroma Baijiu during aging process with fat pork

Soaking aged fat pork is a special aging process in the production of Chi-aroma Baijiu considered to involve the formation of free radicals. This study aimed to investigate the free radicals’ formation pathway in Chi-aroma Baijiu during aged fat pork soaking by using electron paramagnetic resonance (EPR) and spin trapping with 5,5-dimethyl-1-pyrrolin-n-oxide (DMPO). The alkyl radical adducts (DMPO-R) and hydroxyl radical adducts (DMPO-OH) were detected in Baijiu after soaking the fat pork for aging. During the preparation process of aged fat pork, alkoxy radicals adduct (DMPO-RO) were mainly detected since lipid oxidation. Oleic acid and linoleic acid, the two main unsaturated fatty acids in fat pork, produced alkoxy radicals in the oxidation process. The total amounts of spins in linoleic acid and oleic acid after 4-month oxidation treatment increased by 248.07 ± 26.65% and 34.17 ± 0.72% than 0-month. It indicated that the free radicals in aged Chi-aroma Baijiu were mainly derived from the two main unsaturated fatty acids in aged fat pork and linoleic acid had a stronger ability to produce free radicals than oleic acid. Alkoxy radicals (RO·) from fat pork reacted with ethanol in Baijiu to form alkyl radicals (R·). The peroxide bond of hydroperoxides from the oxidation of unsaturated fatty acid was cleaved to form hydroxyl radicals (·OH) that were transferred to Baijiu. The results provide theoretical guidance for the subsequent work of free radicals scavenging.

OXIDATIVE PROCESSES IN GRANULOSA CELLS OF COW OVARIAN FOLLICLES AT FOLLICULAR GROWTH

Article presents the research results on the respiratory activity and redox capacity of granulose layer cells of cow ovarian follicles under the physiological state of follicular growth. After the slaughter of the cows, the ovaries in physiological state of follicular growth were selected and the size of the follicles was evaluated. Cells of the granulosa layer were aspirated from small (< 4 mm), medium (4–7 mm) and large (> 7 mm) follicles and determined: intensity of oxygen absorption – polarographically, redox capacity – potentiometrically. K3[Fe(CN)6] was used as an extracellular electron acceptor. The share of oxygen consumed by aerobic glycolysis was determined by using sodium fluoride inhibitor, the NAD-dependent link of the mitochondrial electron transport chain - amytal, and the terminal (cytochrome oxidase) – sodium azide. The share of free-radical oxidation of unsaturated fatty acids in the realization of oxygen was detected by Na2EDTA.
 Granulosa cells from the ovary of follicular growth are characterized by respiratory activity and regenerative capacity, the intensity of which depends on the size of the follicles from which they are extracted. The highest values of the investigated indicators are characteristic of cells extracted from large follicles, lower – from small follicles, and the lowest values are from medium follicles. The high intensity of oxidative processes in granulosa from small follicles ensures the growth of oocytes, and from large follicles – maturation of the germ cell in the dominant follicle. At the same time, the increased intensity of oxygen consumption by the cells of small and dominant follicles is manifested against the background of limitations in electron acceptors in the extracellular environment.
 The use of inhibitors of ATP resynthesis of both glycolysis and individual links of the mitochondrial respiratory chain testify the activity of the indicated metabolic pathways in granulosa and the possibility of using alternative substrates to ensure the existence of cells. The main way of utilization of oxygen in the granulosa layer cells of small and large follicles is aerobic glycolysis, and from the medium there are alternative ways of supplying and using substrates. The largest flow of reducing equivalents into the extracellular space from the granulosa of a medium-sized follicle due to inhibition of glycolysis indicates that the source of the supply of reducing equivalents into the follicle cavity is glycolysis and this characterizes the dependence of the existence of cells on the indicated metabolic pathway.

The Impact of Fat Deterioration on Formation of Acrylamide in Fried Foods

AbstractThe current study investigates to what extent the reaction products of thermal degradation directly influence acrylamide formation in French fries. The frying tests at 170 and 180 °C are carried out with rapeseed oil for 32 h with 128 frying cycles. Acrylamide content in French fries is determined by LC‐MS/MS. Oxidative and thermal degradation is followed by measuring total polar compounds (TPC), di‐ and polymerized triacylglycerols (DPTG), monomer oxidized triacylglycerols (MONOX), p‐anisidine value (AnV), mono and di‐acyl‐glycerols (MAG and DAG), acid value (AV), epoxy fatty acids, iodine value (IV), saponification value, and fatty acid composition. During frying, the nature and degradation level of the frying medium have a direct impact on acrylamide formation. It can be shown that the pH‐dependent reaction is strongly inhibited at acid values above 0.5 mg KOH g−1 oil. Acidity measured as AV or FFA is mainly caused by oxidation, and less so by hydrolysis of triacylglycerols (TAG) as assumed up to now. Obviously, acid functional groups formed by oxidation of unsaturated fatty acids bound in TAG can act not only as catalyst for dimerization of TAG but also interact with asparagine as most important precursor for acrylamide formation so that no reaction with carbonyl groups for the formation of acrylamide is necessary.Practical applications: The same acidic functional groups that are known to catalyze the formation of dimeric TAG under frying conditions (160–190 °C, access of oxygen) in a nonradical mechanism apparently can also deactivate asparagine by protonization as a potential precursor for the formation of acrylamide. It is recommended not to reduce acidity of used frying oil by active filter aids below AV ≥ 0.5 as it helps to reduce acrylamide contamination of fried food.

Curcumin-loaded emulsions stabilized by the succinylated Antarctic krill proteins: Establishment of photodynamic inactivation to preserve salmon

The succinylated Antarctic krill proteins (SAKP) were fabricated using the ultrasound, and the curcumin-loaded emulsions stabilized by SAKP were selected as photosensitizers to construct a photodynamic inactivation (PDI) system to preserve salmon during storage at 4 °C. The SAKP treated with 200 W ultrasound (SAKP-U-200) presented an expanded and flexible structure, a decreased particle size from 465 nm to 358 nm, an increased surface hydrophobicity from 207.1 to 411.5, and its interface absorption capacity was increased by ∼8.0%, which displayed a superior encapsulation and emulsification ability compared with the other succinylated proteins. The emulsions stabilized by SAKP-U-200 efficiently loaded curcumin, and the established PDI mediated by the coating photosensitizers potently inactivated the bacteria in salmon by ∼3.0 Log10 CFU/g (99.9%) after the illumination of 18.72 J/cm2. Meanwhile, the PDI inhibited the changes of color and pH, maintained the integrity of muscle fibers, and reduced the water loss of salmon during the post-treatment storage. Notably, the PDI treatment inhibited the degradation of proteins by ∼7.7%, and decreased the oxidation of unsaturated fatty acids by ∼21%. Therefore, this study expands the application of PDI in preserving the storage quality of aquatic products.

Metabolomic analysis reveals the responses of docosahexaenoic-acid-producing Schizochytrium under hyposalinity conditions

The heterotrophic Schizochytrium sp. has been utilized to produce docosahexaenoic acids commercially in recent years. However, the high salinity required for Schizochytrium growth and docosahexaenoic acid production could result in salt-induced bioreactor corrosion and high downstream water treatment costs. Thus, exploring the physiological and metabolomic changes of Schizochytrium exposed to low-salt condition is beneficial for developing strategies of reducing the salt concentration during fermentation. In this study, Schizochytrium was exposed to 20, 10, 8, or 6 g/L of sea salt and the responses were determined. It was discovered that biomass accumulation was decreased, while starch and fatty acid was increased, especially unsaturated fatty acid accumulation in Schizochytrium, along with the salt concentration decrease. In addition, the metabolomic analysis showed that the intracellular pool sizes of NADPH, CoA, and ADP-GCS were significantly increased, while those of PEP and Ac-CoA were decreased, consistent with the content changes of fatty acid, starch, and biomass under hyposaline stress. The metabolomic analysis combined with further biochemical evidence revealed that fatty acid content elevation involved strengthening pentose phosphate pathway to provide more NADPH content; elevating CoA content to provide more precursors; upregulating inositol content, which was later demonstrated to enhance fatty acid accumulation; and activating the antioxidant system to reduce oxidation of unsaturated fatty acid caused by the reactive oxidative stress level. Finally, decreased content of glycerol, an important osmoregulator, along with enhanced cell wall polysaccharides, were also discovered in Schizochytrium as an adaptation to low-salt growth conditions. Our paper provides important guidelines for engineering Schizochytrium for low-salt cultivation in the future.

Interrogating Raisin Associated Unsaturated Fatty Acid Derived Volatile Compounds Using HS-SPME with GC-MS.

This study proposed to investigate the generation mechanism of raisins-derived volatile compounds during unsaturated fatty acids oxidation (UFAO) using a mixture of fatty acids (FAs) and four individual FA at different time intervals (0, 4, 8, 12, 16, and 20 days; 60 °C). During the sun-drying of 'Thompson Seedless' grapes (Vitis vinifera L.), a total of 39 UFAO-derived volatiles were characterized by the GC-MS. Firstly a pH value of 4.2 was optimized to proceed with a raisin drying-like UFAO model reaction. Afterward, GC-MS quantification revealed 45 UFAO-derived volatiles, and the maximum numbers of compounds were identified in the interaction of all FAs (39) following linoleic acid (29), erucic acid (27), oleic acid (25), and linolenic acid (27). Pentanoic acid, (E,E)-2,4-octadienal, and n-decanoic acid were only quantified in all FAs, linoleic acid, and erucic acid, respectively. This study showed that all FAs reactions were found to be responsible for the generation of a greater number of UFAO-derived volatiles with higher concentrations.

Effects of low‐pressure radio‐frequency cold plasma on the biochemical parameters and fatty acid profile of wheat flours

AbstractBackground and ObjectivesCold plasma (CP) treatment is a promising way to remove mycotoxins from cereal kernels, although its effects on nutrient contents remain unclear. This study evaluates the biochemical parameters, gelatinization properties, and fatty acid profile of Chinese hard‐white wheat flour treated with low‐pressure radio‐frequency (RF) CP (13.56 MHz, 140 Pa, helium or oxygen, 120 W, 0–180 s, 70 g sample).Findings120 W oxygen and helium plasma respectively required 90 and 120 s treatment to remove 50% deoxynivalenol (DON) from hard‐white wheat flour samples with 1.22 μg/g DON. A General Linear Model–Univariate analysis shows that oxygen and helium plasma both significantly increased water absorption rate, conductivity, and contents of reducing sugars, amylose, soluble protein, and saturated fatty acids in wheat flours but decreased the contents of soluble amino acids, total, unsaturated, mono‐unsaturated and poly‐unsaturated fatty acids, and enthalpy of gelatinization, and kept gelatinization peak temperature. At the same treatment time, helium plasma induced a higher water absorption rate, conductivity, and contents of pentosan and sulfhydryl groups in wheat flours than oxygen plasma. Oxygen plasma induced more reductions in mono‐ and poly‐unsaturated fatty acids in wheat flours than helium plasma. Compared with the untreated samples, helium plasma increased the values of water SRC, NaHCO3 SRC, and sucrose SRC, but decreased the lactic acid SRC, suggesting that the flour functional polymers were modified by helium plasma treatment, but oxygen plasma kept these four SRC values and did not significantly alter the functional polymers in wheat flour.ConclusionThe treatment with low‐pressure RF CP can increase hydrophilicity, and unsaturated fatty acid oxidation in wheat flours while kept starch gelatinization, and helium plasma can modify the flour's functional polymers.Significance and NoveltyThe suitable helium CP treatment (low‐pressure RF, 120 W, and 90–120 s) is a promising way to reduce the contaminants of wheat flours and improve their functional properties.

Effect of sodium alginate coatings enriched with α-tocopherol on quality of fresh walnut kernels

Lipid oxidation of unsaturated fatty acids is the main cause of quality reduction in nuts. To protect the quality of walnut kernels, edible coatings play an important role. Fresh kernels were coated with sodium alginate added with α-tocopherol at concentrations 0.25, 0.5 and 0.75% (w/v) and assessed for moisture content, weight loss percentage, firmness, oxidative stability, nutraceutical potential, color and microbial stability. The results showed that coatings significantly reduced weight loss percentage (20.17 to 11.88 %), peroxide value (2.5 to 1.84 meq o2 /kg), free fatty acid content (1.4 to 0.9 % oleic acid) and microbial count (3.2 to 1.9 log cfu/g) compared to control. In addition, coatings effectively retained total phenolic content (0.88 to 1.07 GAE g−1), DPPH radical scavenging activity (60.13 to 75.12%) and maintained firmness (1.8 to 2.5 N). Alginate enriched emulsion coatings preserved the kernel pellicle color (L* and b*) value and presented high overall acceptable score than the control. Therefore, it is determined that sodium alginate enriched with antioxidants coating could be used as a natural preservative coating material to maintain the postharvest quality of fresh walnut kernels.

Effects of Surface Treatment with Thymol on the Lipid Oxidation Processes, Fatty Acid Profile and Color of Sliced Salami during Refrigerated Storage.

The oxidation of unsaturated fatty acids and the adverse transformation of pigments from meat and spices are the primary causes of chemical degradation in processed meat products. Thymol is found in a variety of plant extracts that have been proven to effectively inhibit or slow down oxidative processes. The objective of our study was to determine whether thymol treatment of the surface of sliced paprika salami could be applied to inhibit lipid oxidation and color change during refrigerated storage. During eight weeks of storage, the malondialdehyde (MDA) levels and the ratios of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), and n6/n3 in thymol-treated salami remained unchanged (p ≥ 0.05), whereas in the controls, the MDA levels increased by approximately twelvefold and the ratio of SFAs in the lipid fraction increased (p < 0.001), while the ratio of PUFAs decreased (p < 0.001). The application of thymol prevented decrease in yellowness (b*) of the slices and reduced decreases in redness (a*) and brightness (chroma).

Fish By-Product Valorization as Source of Bioactive Compounds for Food Enrichment: Characterization, Suitability and Shelf Life.

Fish processing generates many by-products, which are mainly destined for aquaculture feed. However, these by-products have interesting nutritional properties and could still be used for human consumption, thus promoting circular economy. Therefore, this study focused on evaluating the shelf life of mechanically deboned and dried meat (MDDM) of sea bass based on the lipid oxidation criterion (TBARS). The effect of a tocopherol-based antioxidant was also evaluated, and changes in the fatty acid profile were studied. For that, samples with and without antioxidant were stored at three temperatures (37, 55, and 65 °C) for 50 days. This allowed its modelling according to the Arrhenius model. The results showed a shelf life for MDDM of 220 days at 20 °C without the addition of antioxidant. When antioxidant was added, a high protective effect against oxidation and preservation of unsaturated fatty acids was perceived, avoiding nutritional losses and negative sensory effects, reducing EPA and DHA losses by 75% and 72%, respectively. In conclusion, the stability of MDDM from sea bass was demonstrated, making possible its incorporation into other food matrices.

Variations in Antioxidant Capacity, Oxidative Stability, and Physicochemical Quality Parameters of Walnut (Juglans regia) Oil with Roasting and Accelerated Storage Conditions.

Walnut oil, like all vegetable oils, is chemically unstable because of the sensitivity of its unsaturated fatty acids to the oxidation phenomenon. This phenomenon is based on a succession of chemical reactions, under the influence of temperature or storage conditions, that always lead to a considerable change in the quality of the oil by promoting the oxidation of unsaturated fatty acids through the degradation of their C-C double bonds, leading to the formation of secondary oxidation products that reduce the nutritional values of the oil. This research examines the oxidative stability of roasted and unroasted cold-pressed walnut oils under accelerated storage conditions. The oxidative stability of both oils was evaluated using physicochemical parameters: chemical composition (fatty acids, phytosterols, and tocopherols), pigment content (chlorophyll and carotenoids), specific extinction coefficients (K232 and K270), and quality indicators (acid and peroxide value) as well as the evaluation of radical scavenging activity by the DPPH method. The changes in these parameters were evaluated within 60 days at 60 ± 2 °C. The results showed that the levels of total phytosterols, the parameters of the acid and peroxide value, K232 and K270, increased slightly for both oils as well as the total tocopherol content and the antioxidant activity affected by the roasting process. In contrast, the fatty acid profiles did not change considerably during the 60 days of our study. After two months of oil treatment at 60 °C, the studied oils still showed an excellent physicochemical profile, which allows us to conclude that these oils are stable and can withstand such conditions. This may be due to the considerable content of tocopherols (vitamin E), which acts as an antioxidant.

Composition, formation mechanism, and removal method of off-odor in soymilk products.

Soybean is a protein-rich material for plant-based products, and its application in soymilk products is limited due to its off-odor such as beany. In order to explore a solution to address this issue, composition, formation mechanism, and removal methods of the off-odor produced in the processing of soymilk products are comprehensively described in this paper. The main off-odor compounds in soymilk products include hexanal, hexanol, 1-octene-3-ol, (E,E)-2, 4-decadienal, 2-pentylfuran, (E,E)-2,4-nonadienal, (E)-2-nonenal, (E) -2-hexenal, and so on. These odor compounds are mainly produced by the enzymatic and nonenzymatic oxidation of unsaturated fatty acids. At present, physical methods are used to remove off-odor in the industrial production of soymilk products, of which heat treatment is still the most effective. With the development of no beany soybean breeding technology, the combination of multiple methods will become a technical trend for removing off-odor. Some new research directions are also explored about removal methods, which can provide a theoretical reference for the production and technical research of soymilk products.

Effects of phenanthrene on the essential oil composition and leaf metabolome in peppermint plants (Mentha piperita L.)

Polycyclic aromatic hydrocarbons (PAHs) are an important type of persistent organic pollutant that endangers soil ecosystems and human health. Cultivating aromatic plants in PAH-contaminated soils is considered a safe and sustainable phytoremediation strategy to mitigate PAH soil pollution. However, the impact of PAHs on plant essential oils and the metabolic responses within aromatic plants remain unclear. In this study, we investigated the effects of the model PAH phenanthrene (Phe) on the chemical composition of essential oils in the ubiquitous aromatic plant peppermint (Mentha piperita L.) using gas chromatography-mass spectrometry (GC-MS). A total of 56 essential oil components were identified in the plants, among which the ratios of 21 components were significantly altered by Phe exposure. However, the fundamental components of peppermint essential oils including menthol, menthone, menthofuran, and pulegone did not exhibit considerable changes in levels. Thus, Phe stress may have little effect on the primary characteristics of peppermint essential oils. We also evaluated the effects of Phe treatment on metabolome dynamics within peppermint leaves by detecting metabolites in leaves treated with Phe for 0, 1, 3, 5, and 7 days (d) using non-targeted metabolomics. Compared with their corresponding control groups, 26 key different metabolites in the Phe-treated groups were identified and annotated via enrichment analysis with the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Enriched metabolites were primarily involved in the oxidation of unsaturated fatty acids (UFAs), phenylpropanoid metabolism, amino acids, and the formation of vitamin C and caffeine. Phe treatment significantly promoted the oxidation of UFAs, phenylpropanoid metabolism, and histidine production in the first three days of Phe treatment. After 3 d, Phe gradually suppressed the oxidation of UFAs and L-glutamic acid production, while promoting phenylpropanoid metabolism, in addition to the synthesis of vitamin C and caffeine. The dynamic changes in metabolic pathway functioning in Phe-treated peppermint leaves reveal adaptive defensive mechanisms to mitigate Phe stress. This study provides new insights into the responses of aromatic plants toward PAH stress, while also providing a reference for the application of aromatic plants in the phytoremediation of PAH-contaminated soils.