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The present study aimed to investigate the impact of temperature on the quality attributes, particularly lipid oxidation and phospholipid molecular species, of Tai Lake whitebait during hot-air drying. Fresh samples of Tai Lake whitebait were subjected to heat treatment and were dried at temperatures of 40, 50, 60, and 70 °C for 12 h. The results indicated significant and continuous increases in peroxide values (POV), thiobarbituric acid reactive substances (TBARS), and saturated fatty acids (SFA) contents during hot-air drying, but reductions in monounsaturated fatty acids (MUFA). During the hot-air drying process, the mass fraction of triacylglycerol (TAG) and phospholipid (PoL) decreased, while the fractions of diacylglycerol (DAG), monoacylglycerol (MAG) and free fatty acid (FFA) increased. Furthermore, the drying treatment led to a more pronounced reduction in Phosphocholine (PC) content compared to phoethanolamine (PE). A total of 17 phosphatidylcholines (PC), 18 phosphatidylethanolamine (PE), 7 phosphatidylinositol (PI), and 9 phosphatidylserine (PS) molecular species were identified. By comprehensively considering the drying time and quality attributes, 50 °C was selected the ideal temperature for drying. The findings of the investigation revealed that thermal drying significantly influenced the quality attributes and lipid oxidation of Tai Lake whitebait. The insights gained from this study are valuable for improving the drying process for Tai Lake whitebait and enhancing its overall quality. • Lipid oxidation of whitebait were significantly affected by hot-air-drying. • Lipid composition of the Tai Lake whitebait were analyzed comprehensively. • Phospholipid classes in lipid of Tai Lake whitebait was identified. • 50 °C was determined to be the ideal drying temperature for Tai Lake whitebait. [ABSTRACT FROM AUTHOR]

In this study, the effects of different packaging techniques (normal and nitrogen atmosphere, and vacuum packaging) and different storage temperatures (4 and 20 °C) on lipid oxidation in in-shell and kernel walnuts of 'Chandler' and 'Sebin' varieties stored for 12 months were investigated. Free fatty acid, peroxide, p -anisidine, conjugated diene and triene values, hexanal contents, and fatty acid compositions of the walnuts were periodically determined during storage. Free fatty acid values of the samples stored at 20 °C were higher than those stored at 4 °C. Peroxide values of all samples fluctuated during storage but the values determined at the end were higher than their initial values. The highest hexanal and p -anisidine values were observed in the kernels packaged under normal atmosphere and stored at 20 °C. No significant changes were observed in conjugated triene values of the samples. Fatty acid composition was most stable in in-shell walnuts stored at 4 °C. Hexanal contents of the samples stored at 4 °C and the ones packaged under nitrogen and vacuum were remarkably lower than those of the samples packaged under air and stored at 20 °C. As a result, the oxidation reactions were strongly limited in in-shell walnuts of both varieties when stored at 4 °C for 12 months. It was determined that the factors affecting the oxidation reactions in walnuts were in a sequence of storage temperature > presence of the shell > variety > packaging technique. • The shell is a natural protective barrier of walnut against oxidation. • Oil oxidation in walnut was effectively limited when stored in-shell at 4 °C. • Packaging technique did not have significant effect on oxidative stability. • Oxidation progress in walnut varied depending on the variety. [ABSTRACT FROM AUTHOR]

[Display omitted] • The evolution of volatiles in the lean and fat portions of bacon showed different patterns. • The aroma compounds were mainly provided by lean portion, and the optimal drying time was 24 h. • Eight key aroma compounds derived from different lipid fractions and fatty acids. • Linoleic acid was vital for the generation of key aroma compounds in non-smoked bacon. This study explored the evolution of key aroma compounds and their lipid precursors in the lean (LN) and fat (FT) portions of non-smoked bacon during hot air drying. The results showed that the LN portion contained most of the aroma compounds in the bacon (>88%). The volatile content of the FT portion increased as the drying time increased, whereas that of the LN portion reached a maximum within 24 h and then decreased. Based on the highest volatile contents (4889.48 ± 202.06 µg/kg) and sensory scores, 24 h was considered the optimal drying time. For key aroma compounds, hexanal and 2,3-octanedione were derived from free fatty acids and polar lipids. Notably, 1-octen-3-ol was generated only from polar lipids in the FT and LN portions. The 2-undecenal and (E, E)-2,4-decadienal were produced by the oxidation of neutral lipids in the FT portion. Dihydro-5-pentyl-2(3H)-furanone was derived from polar lipids in the LN portion. Altogether, these findings provide theoretical insights into improving the aroma of bacon by optimizing raw material selection and processing methods. [ABSTRACT FROM AUTHOR]

[Display omitted] • Toasted wheat bran protects RP in oil better from oxidation than native wheat bran. • A high bran-to-oil ratio lowers the stabilisation of vitamin A by native wheat bran. • High vitamin A and oil levels limit vitamin A stabilisation by toasted wheat bran. • Toasting reduces the capacity of wheat bran to protect lipids from oxidation. • Vitamin A acts as a pro-oxidant when mixed with oil and toasted wheat bran. Wheat bran stabilises vitamin A (retinyl palmitate, RP) in oil during storage, but the stabilisation mechanism remains unknown. We here studied the effect of the concentration of RP in oil (0.1–2%) and of RP-enriched oil in the system (5–50%) on the RP retention during accelerated storage of systems with native and toasted wheat bran. Generally, toasted bran showed better RP stabilisation than native bran. After four weeks of storage, up to 65% RP was retained in toasted bran systems, whereas the RP retention for native bran was below 10%. For native bran, a higher oil-to-bran ratio and, thus, a lower wheat lipase level resulted in better RP retention. For toasted bran, combined high oil and high RP concentrations resulted in the lowest RP retention. We, therefore, conclude that wheat bran protects RP and lipids from oxidation. This protection is reduced by the pro-oxidative effect of RP, lipid oxidation and lipase. [ABSTRACT FROM AUTHOR]

Summary: Lipid degradation caused by lipolysis and oxidation plays an important role in the evolution of final product quality of cured silver carp. This study aimed to determine the impact of exogenous lipase (ExL) on lipolysis and lipid oxidation during the wet‐curing and dry‐ripening of silver carp inoculated with mixed starter cultures. The addition of ExL to silver carp increased the hydrolysis of total lipids and phospholipids. The free fatty acids (FFAs) content during wet‐curing was significantly higher in the ExL‐treated group compared with the control. Increased FFA accumulation contributed to a high level of conjugated dienes, peroxides and thiobarbituric acid‐reactive substances in the ExL‐treated group, indicating that the lipid oxidation was improved by the addition of ExL. Increased neutral lipase, acid lipase and phospholipase activities during the wet‐curing stage might explain the more extensive release of FFAs in the presence of ExL. The addition of ExL promotes the hydrolysis and oxidation of lipids in cured silver carp. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to study the effect of kiwifruit juice and tumbling in improving tenderness and to access antioxidant potential of kiwifruit juice. Design/methodology/approach: Three treatment groups were made: Spent hen meat was subjected to still marination (SM) and tumbling marination (TM). This meat was used for preparation of whole muscle chicken nuggets and compared with control (without marination) nuggets (Con). These treatments were subjected to analysis of physicochemical characteristics, textural quality, lipid oxidation and sensory quality. Findings: SM and TM exhibited higher moisture content and lower protein and fat content than Control SM and TM showed significant (p = 0.132) reduction in firmness from 5.1 to 2.3 and 1.2 Kg/cm2, respectively, and toughness from 14.1 to 6.2 and 3.3 Kg-sec/cm2, respectively, as observed by Warner-Bratzler shear and improvement in texture profile values. Sensory scores for texture, juiciness and overall acceptability were also better for SM and TM. Significant (p = 0.007) reduction was observed in lipid oxidation parameters of SM and TM. Thiobarbituric acid (TBA) values (on 0 day) for SM and TM were 0.18 and 0.15 as compared to 0.28 mg/kg of malonaldehyde for control. Peroxide values (PV) were also lower for SM and TM as 0.44 and 0.33, which were lesser than control (0.62 meq. peroxide/kg). The values for PV, TBA and free fatty acid increased with increase in storage period in all treatment groups. However, the antioxidant activity of kiwifruit juice persisted during whole storage period evidenced by lower values of lipid oxidation parameters for SM and TM than Control at each storage interval. Research limitations/implications: Further research may be carried out to compare the tenderizing potential of kiwifruit juice with other plant proteases and physical tenderizing techniques. Spent hen meat utilization can be done with greater efficiency by using such techniques in meat caterings. Practical implications: Spent hen meat utilization can done with greater efficiency by using such techniques in meat caterings. Originality/value: Marination with kiwifruit juice improved the quality characteristics of chicken nuggets made from spent hen meat without altering its sensory quality. Tumbling was found to be beneficial in enhancing the tenderizing effect. Therefore, marination with kiwifruit juice can be used as a processing technology to use spent hen meat in preparing value added products. [ABSTRACT FROM AUTHOR]

In order to investigate the generation of aroma in Chinese bacon (unsmoked), the changes of lipolysis, lipid oxidation, and volatile compounds derived from lipid oxidation (VCDFLO) during processing were analyzed. The results showed that acid lipase activity decreased during the entire process, while neutral lipase and lipoxygenase (LOX) increased from raw meat to the 1 day of dry-ripening then decreased. Phospholipase increased during dry-curing then decreased during dry-ripening. Thiobarbituric acid reactive substances increased from raw meat to the 7 days of dry-ripening thereafter decreased. Total free fatty acids increased at the end of 1 day of dry-ripening and decreased subsequently. Thirty-five VCDFLO were identified; the total peak area of these compounds increased by almost double at the 4 days of dry-ripening than raw meat and indicated 47.37-50.85% of total 78 volatile compounds in the final products. In conclusion, VCDFLO generation was attributed to lipid-related enzymes and contributed mainly to the aroma. Practical applications: Chinese bacon (unsmoked) usually produced from high intramuscular fat pork has more intense and long-lasting aroma, since intramuscular triglycerides are good precursors for most volatile compounds. Understanding the mechanism of aroma formation related to lipid oxidation could help us to improve the product quality and optimize the duration of processing. Therefore, the present work identified the characteristic flavor compounds and provided the changing regularity of these compounds at various stages to facilitate the generation of them by regulating lipases and lipoxygenase (LOX) activities. The work showed that neutral lipase and lipoxygenase (LOX) played important roles during dry-curing and dry-ripening. The regulation of lipases and LOX activities can facilitate the generation of volatile compounds of Chinese bacon (unsmoked). [ABSTRACT FROM AUTHOR]

The preservative properties of waste liquor obtained from octopus (Octopus vulgaris) cooking were investigated. Three different concentrations (high, medium, and low) of octopus cooking liquor (OCL) were included, respectively, in the aqueous packaging medium employed for mackerel (Scomber colias) canning. As a result, the canning process led to an increase (p < 0.05) of lipid content, lipid oxidation (development of fluorescent compounds and thiobarbituric acid reactive substances, TBARS), lipid hydrolysis (formation of free fatty acids, FFA) and ω3/ω6 ratio in fish muscle. In all canned samples, primary (peroxides) and secondary (TBARS) levels of lipid oxidation were low. Remarkably, the presence in the packaging medium of the high and medium OCL concentrations led to lower (p < 0.05) lipid oxidation development (fluorescent compound and TBARS detection, respectively). Furthermore, an increasing OCL presence led to an average decrease of peroxide and FFA content and to an average increase of the polyene index (PI). All OCL-packaged muscle showed lower average values of saturated fatty acids and ω3/ω6 ratio and higher average values of PI and monounsaturated fatty acid presence. This study provides a first approach to novel and beneficial use of the present marine waste to inhibit lipid damage of commercial canned fish. [ABSTRACT FROM AUTHOR]

Abstract: Vibrational spectroscopy (mid FTIR and FT-Raman) was used to monitor lipids extracted from hake fillets during frozen storage. Kramer shear resistance was used as a marker of texture changes and lipid damage was also investigated by following the development of conjugated dienes and free fatty acids by spectrophotometric methods. Results show that the intensity of the free fatty acid carboxylic ν(Ceasured by ATR-FTIR spectroscopy can be used for monitoring the development of lipid hydrolysis in hake lipids. Changes in the Raman ν(Ching region (1658cm−1 band), partially attributed to conjugated dienes development, were the only observed spectroscopic alterations related to lipid oxidation of hake lipids during frozen storage at −10°C. The high correlation of free fatty acids with instrumental texture and the disappearance of the ν as(PO2 −) band are consistent with membrane lipid hydrolysis being one of the factors directly related with toughening of lean fish flesh. [Copyright &y& Elsevier]

Abstract: Free fatty acids are strong prooxidants in both bulk and emulsified oils. Addition of oleic acid to an oil-in-water emulsions increased lipid hydroperoxide and hexanal formation at free fatty acid concentrations as low as 0.1% of the lipid. The prooxidant effect of free fatty acids was dependent on fatty acid type with lipid oxidation rates being in the order of linolenic

Free fatty acids (FFA) and lipid and protein oxidation changes during ripening were studied in Torta del Casar cheese. This cheese with protected designation of origin (PDO) is made from raw ewe milk and uses vegetable rennet. Cheeses were analysed at four different stages of ripening at 1, 30, 60 and 90 days. Most FFA significantly increased throughout maturation, except valeric and margaric acids. Acetic acid content increased during ripening and was the most abundant FFA in Torta del Casar cheese at the end of ripening. Short chain fatty acids (SCFA) showed an important increase throughout maturation, especially butyric, isovaleric and isobutyric acids. Lipid oxidation values significantly increased during the first month and decreased in the last 2 months of maturation; however, protein oxidation did not significantly change during ripening. Changes in FFA, especially SCFA, could have great importance in Torta del Casar cheese final characteristics; however, oxidative reactions did not play an important role. [ABSTRACT FROM AUTHOR]

Abstract: The oxidative stability of lipids in processed quinoa was investigated in this study. Ground quinoa was subjected to accelerated aging for 30 days at 25, 35, 45, and 55°C. Three samples were removed from each temperature treatment every 3 days. Free fatty acids, conjugated diene hydroperoxides, and hexanal were used as indicators of lipid oxidation. Storage time and temperature had significant effects (p ⩽0.05) on all three parameters, while the interaction between storage time and temperature was not significant for conjugated diene hydroperoxides produced. The results from these tests suggest that quinoa lipids are stable for the period of time studied. With vitamin E as a naturally antioxidant occurring abundantly in quinoa, the potential for quinoa to be a new oilseed could be enhanced. This study provided some preliminary information on the oxidative stability of quinoa. [Copyright &y& Elsevier]

• A mixture of free fatty acids inhibited lipid oxidation in ground, turkey thigh. • Oleic acid and linoleic acid could convert hemoglobin to hemichrome in spectra. • Increased number of double bonds in FFA facilitated hemichrome formation. • ESR spectra indicates the heme-Fe was in a low-spin state after Hb reacted with FFA. • Hemichrome formation due to added FFA diminished the lipid oxidation capacity of Hb. The pro-oxidant and anti-oxidant effects of free fatty acids (FFA) in meat remain ambiguous. To clarify the role of FFA in lipid oxidation of muscle food, the FFA was added into two systems (turkey mince and washed turkey muscle (WTM)) and lipid oxidation was investigated. A mixture of FFA inhibited lipid oxidation in both systems. The absorbance spectrum of oxyHb and metHb was determined in the presence of C18:1 and C18:2. Conversion to hemichrome spectra was observed and was particularly rapid when metHb was mixed with C18:2. C18:2 was also reacted with metHb followed by a chromatography step to remove unbound C18:2, and termed 'modified Hb'. Electron spin resonance (ESR) spectra of the modified Hb was indicative of hemichrome formation. The modified Hb did not promote lipid oxidation in washed turkey muscle during storage. This suggested that hemichrome formation due to added FFA diminished the lipid oxidation capacity of Hb. [ABSTRACT FROM AUTHOR]

• Understanding of the endogenous factors which effect lipid oxidation are needed. • Myoglobin promoted lipid oxidation in WCM but not WPM. • Two phospholipids (polyenoic indexes: 282, 24) showed similar oxidation rate in WPM. • Muscle microstructure plays critical roles in Mb-mediated lipid oxidation. • Accessibility of phospholipids to Mb was more important than its unsaturation. The roles of lipid oxidation substrates and muscle microstructure in lipid oxidation were investigated in two muscle models (cod and pig). Added myoglobin (Mb) promoted lipid oxidation in washed cod muscle (WCM) but not in washed pig muscle (WPM). The differing microstructure of WCM e.g. more exposed fat cells or membrane of muscle cells compared to the "denseness" or "wrapped" structure of WPM, may have contributed to the better ability of Mb to facilitate lipid oxidation in the WCM. Added phospholipids with polyenoic indexes of 282 and 24 activated Mb as an oxidant similarly in WPM while added neutral lipids and added free fatty acids had little effect. It is suggested that muscle microstructure and accessibility of Mb to phospholipids play critical roles in relation to Mb-mediated lipid oxidation while the degree of unsaturation in the phospholipids was less important. [ABSTRACT FROM AUTHOR]

• Optimum pH values of faba bean lipase and lipoxygenase (LOX) were characterised. • Faba bean had higher lipase activity than oat with triacylglycerols as substrates. • Specific profiles of volatiles from linoleic and α-linolenic acids for faba bean. • Lipid oxidation occurred during preparation of extracts and emulsions. • pH and addition of oil or fatty acids to extracts had a major effect on reactions. Faba bean can respond to the need for plant-based proteins for human consumption. The aim of this work was to study the role of lipid-modifying enzymes in faba bean in causing off-flavour compounds during processing. The faba bean exhibited high lipase and lipoxygenase (LOX) activities, with pH optima being 8.0 and 6.0, respectively. Faba bean LOX preferred free fatty acids (FFAs) over triacylglycerols as substrates, and together with other LOX pathway enzymes, it formed specific volatile products, as measured using headspace solid-phase microextraction–gas chromatography. During the preparation of the food models (i.e. the extracts and emulsions), enzymatic lipid oxidation occurred. The inclusion in the emulsions of rapeseed oil, especially of rapeseed oil FFAs, remarkably increased the amounts of volatile products. The largest quantities of products were formed in food models at pH 6.4, which is close to the pH optimum of LOX. Further studies on lipase in food models are needed. [ABSTRACT FROM AUTHOR]