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[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]

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

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]