Thermal oxidation mechanism of palmitic aicd.

The oxidation and degradation of fats lead to a decrease in the nutritional value of food and pose safety concerns. Saturated fatty acids also hold a significant position in the field of lipid oxidation. In this study, the oxidation products of methyl palmitate were investigated by using gas chromatography mass spectrometry (GC-MS). Seven monohydroperoxides and 72 secondary oxidation products were detected. Combined with density functional theory (DFT) calculations, the formation mechanisms of oxidation products can be summarized into four stages. The initial stage involved the formation of monohydroperoxides and alkanes, followed by the subsequent stage involving methyl x-oxo(hydroxy)hexadecanoates. The third stage involved the formation of methyl ketones, carboxylic acids, and aldehydes, while the final stage involved lactones. Meanwhile, methyl ketones were the most abundant oxidation product, approximately 25 times more abundant than aldehydes; the calculated results agreed well with the experimental results. The establishment of a comprehensive thermal oxidation mechanism for palmitic acid provided a new foundation for future lipid oxidation analyses.

An Insight into the Thermal Degradation Pathway of γ-Oryzanol and the Effect on the Oxidative Stability of Oil.

Thermal stability and antioxidant ability of γ-oryzanol in oil have been widely studied. However, further research is needed to explore its thermal degradation products and degradation pathways. The thermal degradation products of γ-oryzanol in stripped soybean oil were identified and quantified by employing high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) during heating at 180 °C. The results revealed that γ-oryzanol undergoes ester bond cleavage to form trans-ferulic acid and free sterols, and trans-ferulic acid generated intermediate compound 4-vinylguaiacol, which ultimately generated vanillin. Analysis of kinetic and thermodynamic parameters revealed the thermal stability ranking of the four components of γ-oryzanol as follows: CampFA > CAFA > 24MCAFA > SitoFA. Furthermore, γ-oryzanol exhibited superior antioxidant activity at lower temperatures. The results of this study provide a theoretical basis for a better understanding of the thermal stability and antioxidant properties of γ-oryzanol in oil under thermal oxidation conditions.

Mechanisms of the Formation of Nonvolatile and Volatile Oxidation Products from Methyl Linoleic Acid at High Temperatures.

The impact of the oxidation of linoleic acid cannot be overlooked in daily food consumption. This study used gas chromatography-mass spectrometry (GC-MS) to identify both nonvolatile oxidation products and volatile oxidation products of methyl linoleic acid at 180 °C and density function theory to investigate oxidation mechanisms. An analysis of nonvolatile oxidation products revealed the presence of three primary oxidation products. The three primary oxidation products were identified as hydroperoxides, peroxide-linked dimers, and heterocyclic compounds in a ratio of 2.70:1:3.69 (mmol/mmol/mmol). The volatile components of secondary oxidation products were found including aldehydes (40.77%), alkanes (19.89%), alcohols (9.02%), furans (6.11%), epoxides (0.46%), and acids (2.50%). DFT calculation proved that the secondary oxidation products mainly came from peroxides (77%). Finally, we look forward to our research contributing positively to lipid autoxidation and human health.

Zeaxanthin Combined with Tocopherol to Improve the Oxidative Stability of Chicken Oil.

Chicken oil is prone to oxidation due to the high content of unsaturated fatty acids. The interaction of antioxidants was affected by their concentration, ratio, and reaction system. In this article, mixtures of zeaxanthin and tocopherols (α-tocopherol and γ-tocopherol) were chosen to enhance the oxidative stability of chicken oil. The antioxidation of zeaxanthin with tocopherols was analyzed using the Rancimat test, the free radical scavenging capacity and the Schaal oven test (the variation of antioxidant content, PV and shelf life prediction). The optimal concentration of zeaxanthin determined by Rancimat in chicken oil was 20 mg/kg. The binary mixtures have a strong synergistic effect in the ABTS experiment, and the clearance rate was up to 99%, but antagonistic effect in ORAC. The degree of synergism between zeaxanthin and tocopherols was determined by ratio. The interaction between zeaxanthin and α-tocopherol was synergistic, while the types of interaction between zeaxanthin and γ-tocopherol were affected by concentration. The main synergistic interaction mechanism was the regeneration of tocopherol by zeaxanthin. Synergistic combinations of zeaxanthin with α-tocopherol and γ-tocopherol played a key role in the primary oxidation stage of the lipid. The best synergistic combination was A3 (zeaxanthin+α-tocopherol: 15+50 23 mg/kg), which could extend the shelf life of chicken oil (92.46 d) to 146.93 days. This work provides a reference for zeaxanthin and tocopherol to improve the oxidative stability of animal fat.

Study of the Antioxidant Capacity and Oxidation Products of Resveratrol in Soybean Oil.

Resveratrol (3,5,4'-trihydroxystilbene), a naturally occurring polyphenol that is widely utilized in functional food due to its antioxidant, anti-inflammatory, anti-cancer and anti-aging properties. In the present study, the antioxidant capacity and oxidation products of resveratrol in soybean oil were investigated. The antioxidant activity of resveratrol was evaluated by employing various in vitro antioxidant assays such as DPPH scavenging activities, ferric reducing abilities (FRAP) and oxygen radical absorbance capacity (ORAC). Furthermore, monitoring the peroxide value and the acid value of soybean oil with the addition of 200-1000 µg/g of resveratrol at 60 and 180 °C. It was found that when the concentration of resveratrol in soybean oil was 600 µg/g, the antioxidant capacity was most effective. Resveratrol and its thermal degradation products were identified using liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS). There were seven nonvolatile oxidation products with mass-to-charge ratios of 138.03, 171.04, 185.10, 157.03, 436.13, 244.07 and 306.09 kg/C and two volatile oxidation products with mass-to-charge ratios of 100.05 and 158.13 kg/C were identified. The research findings may provide essential information for the development of resveratrol as functional oils in future.

Inhibiting Effects of Ginger and Rosemary on the Formation of Heterocyclic Amines, Polycyclic Aromatic Hydrocarbons, and Trans Fatty Acids in Fried Pork Balls.

The preparation of fried meat products is prone to the formation of large amounts of heterocyclic amines (HCAs), polycyclic aromatic hydrocarbons (PAHs), and trans fatty acids (TFAs), which are potential risks to human health. Spices contain natural antioxidants that can inhibit the oxidation of fats and oils and the formation of hazardous substances. In this experiment, the effect of adding different levels (0.25%, 0.75%, 1.25%) of ginger or rosemary during meatball preparation on the formation of HCAs, PAHs and TFAs in fried pork balls was investigated. The results showed that the addition of ginger and rosemary reduced the content of HCAs in fried pork balls compared to the control group (no added spices). The inhibition of total HCAs was 63% when 0.25% ginger was added, while the total HCA content was reduced to 59% when 0.25% rosemary was added. The addition of 0.25% and 0.75% rosemary reduced the PAH content in fried pork balls by 30% and 35%. In addition, ginger and rosemary showed significant inhibition of C20:1 11t in TFAs, with a maximum inhibition rate of 40%. Therefore, adding appropriate levels of ginger or rosemary to fried pork balls could simultaneously inhibit the formation of HCAs, PAHs, and TFAs.

Mechanism of the initial oxidation of monounsaturated fatty acids.

The development of detection technology prompts the need to elaborate on the theory behind the oxidation of unsaturated fatty acids. This study integrates the detection of monounsaturated fatty acid oxidation at 60 °C with computational simulations to provide an advanced theoretical basis for the formation of hydroperoxides and allyl. The results indicate that oxidation reaction led to increases of 3.4 mg/g for 8-hydroperoxy-trans-9-octadecenoate (trans8) and 2.7 mg/g for 9-hydroperoxy-trans-10-octadecenoate (trans9) and 10-hydroperoxy-trans-8-octadecenoate (trans10) despite low temperatures. The energy of peroxyl radical production was 0.36 kcal/mol and that of allylic isomerization was 78.52 kcal/mol, indicating the existence of two pathways for hydroperoxides formation: ß-fragmentation and the allylic isomerization. Structural equation modeling (SEM) verified the multistep competitive side reactions that occurred during oxidation. This finding provides a new basis for future analysis of lipid oxidation.

Impact of Heating Temperature and Fatty Acid Type on the Formation of Lipid Oxidation Products During Thermal Processing.

Thermal treatment of lipids rich in fatty acids contributes to the formation of lipid oxidation products (LOPs), which have potentially harmful effects on human health. This study included soybean oil (SO), palm oil (PO), olive oil (OO), and lard oil (LO) as the research objects, with an aim to investigate the impact of heating temperature and fatty acid type on the generation of LOPs (α-dicarbonyl compounds, malondialdehyde (MDA), α,ß-unsaturated aldehydes, and 16 volatile aldehydes). Results showed that LOPs increased significantly (p < 0.05) with the increase in temperature (100 ~ 200°C). Furthermore, the amount of 2,3-butanedione (159.53 µg/g), MDA (3.15 µg/g), 4-hydroxy-hexenal (3.03 µg/g), 2-butenal (292.18%), 2-pentenal (102.26%), hexanal (898.72%), and 2,4-heptadienal (E, E) (2182.05%) were more at 200°C in SO rich in polyunsaturated fatty acids (PUFAs) than other oils. Results from heat map analysis indicated that the 2, 4-heptadienal, and glyoxal related to the myristic acid of oil. Moreover, the MDA was in close association with PUFAs. Based on the effect of temperature and fatty acid type on the generation of LOPs, this study could serve as a control method to reduce harmful LOPs.

Multiple Recognition-Based Sensor for Pesticide Residues.

The use of pesticides is gradually increasing to improve the yield and quality of crops. However, excessive pesticide use has led to a dramatic pollution increase in the environment and agricultural products, posing severe human health risks. Therefore, rapid, sensitive pesticide detection is essential. Various pesticides detection methods and products have been developed in recent years. This brief review summarized the point-of-care testing (POCT) detection of pesticides based on multiple recognition, including protein-, aptamer-, nanomaterial-, and macrocycle-based recognition. The review aimed to address the growing demands for regulating and destroying pesticides or other adverse agriculture-related applications in the real world.

Effect of tempered procedures on the crystallization behavior of different positions of cocoa butter products.

The effects of tempered procedures (well and under-tempered) on the crystalline behaves of cocoa butter were elaborated through detecting crystalline structure and compositions of crystals located at different positions of cocoa butter products in this study. The under-tempered products couldn't form crystalline structures as uniform as the well-tempered ones, whose internal contained more low saturated triacylglycerol and structurally unstable crystals. The low saturated triacylglycerol further created the diverse microstructure and thermal properties between center and outer part of cocoa butter products. During storage, the concentration differences drive migration of low saturated triacylglycerol from center to outer part of the product. Although this reduces the differences in triacylglycerol composition, it results in the polymorphism conversion between ß'-IV and ß-VI form and the fat bloom formation. This work indicates that the monitor for crystalline properties of different positions in cocoa butter products helps the chocolate industry to control formation of fat bloom.

Effects of Human, Caprine, and Bovine Milk Fat Globules on Microbiota Adhesion and Gut Microecology.

Milk fat is an essential nutrient for infant development. The effects and mechanisms of human, caprine, and bovine milk fat globules (MFGs) on the gut microbiota were investigated in this study. Human MFGs enhance the efficacy of probiotics by inhibiting pathogen function. Akkermansia and Bifidobacterium were identified as the dominant microbiota by human MFGs. Mucin and complement inhibitory proteins in human MFGs were found to inhibit different pathogens. Caprine MFGs directly promoted the colonization of probiotics and the emergence of the biomarker Allobaculum. Mucin 1 in caprine MFGs was primarily responsible for inducing probiotic adhesion. Bovine MFGs increased the abundance of Oscillospira, which reduces the risk of obesity. Due to the enrichment of cell-cell junction proteins and the lack of mucin, the regulation of gut microecology by bovine MFGs was not readily apparent. In short, this study paves the way for the development of functional infant formula.

Dairy Processing Affects the Gut Digestion and Microecology by Changing the Structure and Composition of Milk Fat Globules.

Milk fat globules (MFGs) are the major source of energy for infants' dietary intake. In this study, the effects of changes in the structure and composition of MFG after dairy processing on lipolysis and immune regulation were investigated. Pasteurized MFG tends to form protein aggregates to prevent lipolysis. However, the aggregate is rich in neutrophil degranulation products, which are effective in killing pathogens. Homogenized MFG has the lowest hydrolysis rate due to the reconstituted anti-lipase barrier and exposed apolipoprotein. Simultaneously, the reconstituted barrier can compensate for the lack of the complement cascade. Spray-dried MFG had the highest hydrolysis rate attributable to the disrupted MFG barrier and the release of lipoprotein lipase and endothelial lipase. The immunomodulatory properties of spray-dried MFG proteins are mainly mediated by the toll-like receptor (TLR) signaling pathway. This research provides the improvement basis of dairy processing and functional infant formulas.

Effects of Low-melting-point Fractions of Cocoa Butter on Rice Bran Wax-corn Oil Mixtures: Thermal, Crystallization and Rheological Properties.

The fatty acid compositions, polymorphism, solid fat content (SFC), thermal properties, microstructure and rheological properties of fat blends of rice bran wax and corn oil (RWC) with low-melting-point fractions of cocoa butter (LFCB) in the range of 20-50% were investigated. With the raising content of LFCB, the hardness, SFC, storage modulus (G') and loss modulus (G'') of blend samples increased. The unsaturated fatty acids of blend samples with different LFCB proportion were in the range of 60.42% to 71.25%. Two kinds of polymorphism were observed in blend samples, which were ß'-Form and ß-Form. During the crystallization process, the rice bran wax was first crystallized, and then induced a part of LFCB formed ß'-Form crystals and another LFCB formed the ß-Form crystals. The results show that the addition of LFCB could improve the plasticity of fat blends and reduce the difference in properties between them and commercial shortening.

The Effect of Cooling Rate on the Microstructure and Macroscopic Properties of Rice Bran Wax Oleogels.

The main purpose of this paper is to study the microstructure and macroscopic characteristics of rice bran wax (RBW) oleogels at a cooling rate of 1°C/min and 10°C/min by polarized light microscopy, X-ray diffraction, differential scanning calorimetry, texture analyzer, and micro rheometer. The oleogels of soybean oil were prepared by RBW in concentrations of 5%, 7.5%, 10%, 15% and 20% (wt/wt). The results of this study indicated that the concentration of RBW and cooling rates were affected by the crystal size and spatial distribution of these crystals. For the same RBW concentration, oleogels contained smaller crystals when cooled at 10°C/min compared to 1°C/min. And the oleogels obtained at a rate of 10°C/min exhibited a tighter crystal network, lower melting point, harder texture, and energy storage modulus. These results demonstrated the impact of cooling rate on the rheological behavior, nucleation, and crystallization process.

Zeaxanthin in Soybean Oil: Impact of Oxidative Stability, Degradation Pattern, and Product Analysis.

In this study, the antioxidant capacity and oxidative stability of zeaxanthin with different concentrations in soybean oil were evaluated. The oxidative or isomerization products of zeaxanthin were monitored during oxidation for 12 h at 110 °C. It was found that the ability to scavenge the free radicals (DPPH, FRAP, and ABTS) was dependent upon the concentration of zeaxanthin. However, antioxidation of zeaxanthin was observed when the concentration was less than 50 µg/g. When the concentration exceeded 50 µg/g, zeaxanthin acted as a pro-oxidant. There were three kinds of non-volatile products of zeaxanthin that were detected: (a) Z-violaxanthin, (b) 9-Z-zeaxanthin, and (c) 13-Z-zeaxanthin, and it was found that the content of 13-Z-zeaxanthin formed by isomerization was the highest. In addition, the linear ketone (6-methyl-3,5-heptadien-2-one) and cyclic volatile products (3-hydroxy-ß-cyclocitral, 3-hydroxy-5,6-epoxy-7,8-dihydro-ß-ionone, and 3-hydroxy-ß-ionone) formed by in situ oxidative cleavage were identified.

The Relations between Minor Components and Antioxidant Capacity of Five Fruits and Vegetables Seed Oils in China.

The seed of five fruits and vegetables, which are often eaten by Chinese people, were selected as research objects to study the physicochemical properties, nutritional ingredients and antioxidant capacity of their seed oils. The fatty acid results indicated that the oleic acid was the main unsaturated fatty acid in almond oil and celery seed oil (content of 64.10% and 62.96%, respectively), and the wax gourd seed oil, watermelon seed oil and pumpkin seed oil were linoleic acid as the main unsaturated fatty acid (content of 72.45%, 76.77% and 47.35%, respectively). Unsaturated fatty acids are mainly located at the sn-2 position of the triacylglycerol (TAG), whereas saturated fatty acids are mainly located at the sn-1, 3 positions for the five seed oils. The pumpkin seed oil had certain advantages in terms of phytosterols and squalene (3716 and 2732 mg/kg, respectively). The high content of polyphenol for celery seed oil exhibits higher medicinal value. Polyphenols, and brassicasterols were have significant correlation with antioxidant capacity (p < 0.05, r = 0.890-0.998). The significant differences in nutrient composition between these fruits and vegetables seed oils indicate their unique value as food.

Molecular Reaction Mechanism for the Formation of 3-Chloropropanediol Esters in Oils and Fats.

3-Chloro-1,2-propanediol fatty acid esters (3-MCPD esters) are a group of process-induced contaminants that form during the refining and heating of fats and oils. In this study, a combined method of simulated deodorization and computational simulation was used to explore the precursor substance and the generation path of 3-MCPD esters. From the results, 3-MCPD esters reached a content level of 2.268 mg/kg when the diacylglyceride (DAG) content was 4% and temperature was 220 °C. A good correlation was observed between DAG and 3-MCPD ester contents ( y = 0.0612 x2 - 1.6376 x + 10.558 [ R2 = 0.958]). There were three pathways for the formation of 3-MCPD esters: (A) a direct nucleophilic substitution reaction, (B) an indirect nucleophilic substitution reaction, and (C) a mechanism of an intermediate (glycidyl ester) from the calculation of Gaussian software at the B3LYP/6-31+g** level. The data showed that the ester-based direct nucleophilic substitution reaction was the most likely reaction pathway. The energy barriers for the formation of the 3-MCPD esters dipalmitin, diolein, and dilinolein were 74.261, 66.017, and 59.856 kJ/mol, respectively, indicating that the formation process of 3-MCPD esters is a high-temperature endothermic process. Therefore, by controlling the introduction of precursor (DAG) and reducing the temperature, 3-MCPD ester formation was prevented.

Mechanisms of isomerization and oxidation in heated trilinolein by DFT method.

In order to investigate the molecular mechanisms of the heat-induced cis/trans isomerization and oxidative cleavage of trilinolein, a highly purified sample was heated at a range of temperatures (120, 140, 160, 180, 200, 220 °C) for 5 h. The reaction process of cis/trans isomerization of C18:2 was studied by a combination of the gas chromatogram (GC) method with density functional theory (DFT). When trilinolein was heated to 180 °C, a small amount of trans/trans C18:2 was obtained (0.074 mg g-1). As the temperature increased to 220 °C, the amount of trans C18:2 reached 0.198 mg g-1. This study shows that C18:2-9c12t and C18:2-9t12c were the main trans fatty acids in heated trilinolein. The molecular mechanisms of isomerization and oxidative cleavage were verified by Gaussian 09 W software. All the geometry was optimized using DFT at the B3LYP/6-31*G level. The energy difference between cis and trans linoleic acid was equal to 6.2 kJ mol-1. Therefore, vegetable oil with a higher linoleic acid content should be maintained at 140 °C or less to avoid the formation of trans linoleic acid.

Cationic amphiphilic microfibrillated cellulose (MFC) for potential use for bile acid sorption.

In this work, Micro-fibrillated Cellulose (MFC) was cationically modified by quaternary ammonium groups with different chemical structures aiming to improve the sorption capacity to bile acid. The in-vitro bile acid sorption was performed by investigating various factors, such as quaternary ammonium group content and length of its alkyl substituent of the modified cationic MFC (CMFC), ionic strength, initial concentration and hydrophobicity of bile acid. The results showed that the sorption behavior of the modified CMFC was strongly influenced by the quaternary ammonium group content and the lengths of its alkyl substituent, the sorption capacity for the modified CMFC with a C18 alkyl substituent, was approximately 50% of that of Cholestyramine. The experimental isotherm results were well fitted into the Temkin model. The effect of salts in the solution was smaller for the bile acid sorption onto the hydrophobic CMFC than the CMFC. It was also found that the binding capacity of CMFC was higher for more hydrophobic deoxycholate in comparison with cholate.

Mechanism of formation of trans fatty acids under heating conditions in triolein.

To elucidate the relationship between heat-induced cis/trans isomerization and reaction temperature and energy in unsaturated lipids, we investigated the molecular mechanism of the heat-induced cis/trans isomerization of 18:1 isomers. Triolein (18:1,9c) was heated at two range temperatures (130, 160, 190, 220 °C and 135, 140, 145, 150, 155 °C) and analyzed by the gas chromatography (GC) method. When the heating temperature increased to 150 °C, the amount of trans 18:1n-9 changed from 0.0897 mg/g oil (1 h) to 0.1700 mg/g oil (3 h). This study shows that the cis to trans isomerization may occur at 150 °C. The formation of fatty acid isomers followed a proton transfer route. All key geometries, transition states, intermediates, and bond dissociation energies (BDE) were optimized at the B3LYP/6-31G* level for the density functional theory (DFT). The zero-point energy corrections of the isomers were carried out using calculations at the B3LYP/6-311++G** level. The calculated energy difference between the cis and trans oleic acid was equal to 7.6 kJ/mol, and the energy barriers of the transition from cis 18:1n-9 to trans 18:1n-9 were 294.5 kJ/mol. The intrinsic reaction coordinates (IRCs) were obtained to be used as an expression of the reaction route and to analyze the transition states and intermediates. The study results suggest that the heating temperature should be kept under 150 °C, to avoid the risk of trans fatty acid (TFA) intake in daily food.