Oxidation in Low Moisture Foods as a Function of Surface Lipids and Fat Content

The development of volatile off-flavor compounds in soy protein isolates and plant meat during storage

The off-flavor associated with soy protein isolate (SPI) has negatively impacted the full acceptance of plant meat. This study investigated the factors that contribute to the development of volatile compounds as well as the volatile compounds responsible for the off-flavors. The main objective of this study was to investigate the formation of volatile off-flavor compounds in soy protein isolates and plant meat during storage. The samples were stored at 4 ± 0.5 °C, 25 ± 2 °C, and 37 ± 1 °C for durations of 0, 2, 4, 6, and 8 weeks, respectively. They were investigated using physicochemical properties, sensory, electronic nose (E-nose), and gas chromatography-mass spectrometry (GC-MS). The volatile off-flavor compounds were identified and plant meat exhibited significantly higher levels of off-flavors than SPI. Oil bodies, excessive moisture, elevated temperature, and extended storage were recognized as the main factors contributing to the development of off-flavors. Therefore, the extended storage of SPI and plant meat resulted in a continuous reaction that eventually caused the development of volatile off-flavor compounds.

Inclusion of Pineapple By-Products as Natural Antioxidant Sources in Diets for European Sea Bass (Dicentrarchus labrax)

This study investigates the effects of pineapple by-products on feed preservation during storage at two different temperatures (25 °C and 4 °C) and on European sea bass (Dicentrarchus labrax) stress resistance. Four isoproteic, isolipidic, and isoenergetic diets were manufactured: CTRL-negative control, commercial diet without added antioxidants; VITE-positive control, CTRL diet with 100 mg kg-1 of vitamin E; and P2 and S2-VITE diet with 2% pineapple peel or stem flour, respectively. The fish (13.5 ± 0.8 g) were split into four replicate groups per diet and fed ad libitum for 12 weeks, after which they were subjected to a stress challenge of air exposure (1 min) followed by confinement (5 min, 100 kg m-3). Despite storage time lowering the antioxidant properties of all diets, P2 and S2 showed increased antioxidant capacity (DPPH•, ABTS•+, and ORAC) before and after storage. The diets were well accepted by the fish, and the VITE-fed fish showed significantly lower lipid peroxidation values in the liver and muscle compared to all remaining diets. However, pineapple by-product inclusion did not result in increased fish stress resistance. Further optimization is required for the successful use of pineapple by-products as natural antioxidants in aquafeeds.

Effects of Temperature on the Microbial Growth and Quality of Unsealed Dry Pet Food during Storage

Dry pet food is a convenient option for pet owners, but its storage conditions can impact its microbial growth and quality. In this study, we examined the effects of storage temperature on the quality and microbial growth of dry pet food. The pet food was stored at 25°C and 35°C, respectively, and samples were analyzed on days 0, 30, 90, and 120 for microbial growth and quality attributes such as pH, color, lipid oxidation, and volatile basic nitrogen. While no initial microbial growth was observed due to the low water content and water activity, quality attributes showed changes over time. However, the changes were negligible, indicating that dry pet food remains feedable for up to 120 days even at a storage temperature of 35°C. These findings suggest that dry pet food can be safely stored at room temperature or up to 35°C without compromising its quality.

Lipid oxidation in foods and its implications on proteins

Lipids in foods are sensitive to various environmental conditions. Under light or high temperatures, free radicals could be formed due to lipid oxidation, leading to the formation of unstable food system. Proteins are sensitive to free radicals, which could cause protein oxidation and aggregation. Protein aggregation significantly affects protein physicochemical characteristics and biological functions, such as digestibility, foaming characteristics, and bioavailability, further reducing the edible and storage quality of food. This review provided an overview of lipid oxidation in foods; its implications on protein oxidation; and the assessment methods of lipid oxidation, protein oxidation, and protein aggregation. Protein functions before and after aggregation in foods were compared, and a discussion for future research on lipid or protein oxidation in foods was presented.

Role of Solid Fat Content in Oxidative Stability of Low-Moisture Cracker Systems

Lipid oxidation is a major pathway for the chemical deterioration of low-moisture foods. Little is known about how the physical properties of the fat used in crackers impact lipid oxidation kinetics. Fully hydrogenated soybean fat + interesterified soybean oil, fully hydrogenated soybean fat + sunflower oil, fully hydrogenated soybean oil, and soybean oil and interesterified fat alone were formulated to have varying solid fat content (SFC) at 55 °C but the same linoleic acid and tocopherol contents, so the fats had similar susceptibility to oxidation. A fluorescence probe showed that lipid mobility increased with decreasing SFC in both cracker doughs and fat blends, suggesting the probe could be used to monitor SFC directly in foods. Decreasing SFC decreased oxidation in crackers. Crackers made from interesterified fat (13.7% SFC) were more oxidatively stable (hexanal lag phase = 33 days) than crackers made from fat blends (hexanal lag phase = 24 days). These results suggest that blended fats result in regions of liquid oil high in unsaturated fatty acids within a food product prone to oxidation. Conversely, interesterified fats where unsaturated and saturated fatty acids are more evenly distributed on the triacylglycerols are more stable. Thus, interesterified fats could allow for the formulation of products higher in unsaturated fatty acids to improve nutritional profiles without sacrificing shelf life.

The effect of roasting, storage temperature, and ethanoic basil (Ocimum basilicum L.) extract on the oxidative stability of crude sesame (Sesamum indicum L.) oil

Sesame (Sesamum indicum L.) is an annual oilseed crop that is widely used for crude sesame oil (CSO) extraction. CSO is unrefined, thus, may impact the storage stability due to the uncontrolled processing and handling conditions, and absence of preservatives. The purpose of this study intends to analyze the fatty acid profile and oxidative stability of CSO. In a complete randomized (2*2*2) factorial design, clean sesame seeds (3.92% moisture content) were used for oil extraction with/without roasting treatment (200°C). The fatty acid profile and oxidative value of the CSO were analyzed. The roasted sesame seed oil extraction yield was higher (50.9%) and composed of 83.15% unsaturated fatty acids with an omega-6 to omega-3 ratio of 95.3. The ratio of polyunsaturated fatty acids (PUFAs) to saturated fatty acids (SFAs) was 2.9, while the moisture content of the CSO was 0.37%, exceeding the tolerable limit. The predominant fatty acids of CSO include palmitic, stearic, oleic, and linoleic acids. Elevated thermal condition during processing and handling speeding up oxidation exceeded the tolerable limit after 25 days of storage, while the ethanoic basil extract was found to inhibit oxidation in the range of 16.38%-90% (p-value < .05). The peroxide value (PV), para-anisidine value (p-AV), and total oxidation (TOTOX) value of CSO with 50 ppm (parts per million) basil extract were detected within the range of 0.29-3.92, 0.75-2.59, and 1.57-8.6 milliequivalents (meq) O2/kg oil, respectively, below the tolerable limit. Nevertheless, basil extract's antioxidant property was declined during prolonged storage, in particular, at elevated temperature. The use of organic extracts of locally available sweet basil herb is capable of mitigating oxidation and substituting inorganic antioxidant for a healthier diet.