Effect of clove extract pretreatment and drying conditions on lipid oxidation and sensory discrimination of dried omena (Rastrineobola argentea) fish

Sun‐drying is a low‐cost, low‐technology fish preservation method frequently employed in developing areas. However, the process promotes lipid oxidation and its associated undesired flavours and odours. This study investigated low‐technology solutions for impact on lipid oxidation and sensory attributes of oven‐dried omena fish (Rastrineobola argentea). Two oven‐drying conditions and four doses of clove water extract ‘dip’ pretreatments were studied in a complete factorial design. Lipid oxidation in dried fish was assessed by TBARS, peroxide value and fatty acid analysis by GC‐FID. Results showed that soaking in 10 g L^?1 clove water extract for 1 h and oven‐drying at 150 °C × 30 min significantly reduced TBARS and peroxide values in omena fish by 77% and 79%, respectively, and polyene index showed improved retention of long‐chain polyunsaturated fats, compared to original drying condition. Lastly, panellists of a triangle test were able to discriminate between biscuits made with the modified and original dried fish.     

Glycerol and Acetate Additions to Maximize Lipid Content in High-Density Cultures of Phagotrophic Alga Ochromonas danica

Waste organics conversion to algal lipid is environmentally friendly and it promotes sustainability. Achieving high-lipid content in cells is crucial to the economic feasibility of algal lipid production and collection. Here, a phagotrophic microalga Ochromonas danica was grown on waste ketchup and then stimulated to accumulate high-lipid content using glycerol and acetate. Individually, glycerol and acetate could increase lipid synthesis. Sequential glycerol-then-acetate addition was more effective; for an O. danica culture with 0.25 g L⁻¹ cells, the intracellular lipid content was increased to 70–80% (w/w) in 6–12 hours. However, acetate added at >1 g L⁻¹ damaged cells. For high-density (25 g L⁻¹) fermentations, glycerol and acetate addition strategies were evaluated to overcome this inhibition. Results indicated that glycerol could be added in batches or continuously as long as the amount was sufficient to satisfy the glycerol consumption rate of 6 mg (g cells-hour)⁻¹ while acetic acid needed to be added continuously, optimal at a rate of 0.27–0.30 g hour⁻¹ or 12–14 mg (g cells-hour)⁻¹. Intracellular lipid content could reach 70–80% after 2-day supplementation of glycerol and acetic acid. The methods of glycerol/acetate additions developed here enhance algal lipid production and enable effective conversion of organic wastes to algal lipids as sustainable bioproducts.     

Evolution of oxidative and structural characteristics of proteins,especially lipid transfer protein 1 (LTP1) in beer during forced-ageing

The evolution of oxidative and structural characteristics of proteins, especially lipid transfer protein 1 (LTP1), in beer during forced-ageing was examined. The oxidative characteristics of beer and proteins were evaluated by DPPH radical scavenging activity and ABTS radical cation scavenging activity. Results showed that the levels of proteins, thiols, LTP1 and antioxidant activity decreased gradually. This was accompanied by the degradation of macromolecular proteins in beer during forced-ageing. Results from circular dichroism (CD), Fourier-transform infrared spectroscopy (FTIR), surface hydrophobicity (S₀) and ζ-potential further indicated that the secondary and tertiary structure of LTP1 changed drastically during forced-ageing, with the reduction of the S₀, α-helix and β-sheet contents and the increase in negative ζ-potential and random coil. Thus, the proteins, especially LTP1, might play important roles in maintaining oxidative stability of beer.     

The production of volatile compounds in model casein systems with varying fat levels as affected by low-frequency ultrasound

The effects of low-frequency ultrasound on the production of volatile compounds in model casein protein systems containing various fat concentrations of 2%, 4% and 6% (w/w) were investigated. Ultrasound application was performed at 20 kHz for up to 10 min which corresponded to energy densities ranging from 9.54 to 190.8 J mL⁻¹. Similar volatile compounds were detected both in pure fat and mixtures of casein and fat (CF) systems. These volatiles belonged to the groups of aldehydes, ketones, esters, alcohols and hydrocarbons, which were the products of oxidation of lipids or protein degradation due to acoustic cavitation. The amount of fat in the casein systems had minor effects on the production of volatiles, whereas the production of volatile compounds was significantly affected by the ultrasound treatment. Short sonication times <5 min generated similar volatile profiles to the untreated samples. In contrast, prolonged sonication for 5 and 10 min considerably increased the production of volatile compounds and the amounts of fatty acids. Thus, the application of low–frequency ultrasound for short periods should be considered to minimise the production of volatile compounds which can ultimately affect the taste.     

A trout (Oncorhynchus mykiss) perfusion model approach to elucidate the role of blood removal for lipid oxidation and colour changes in ice-stored fish muscle

Whole body saline-perfused rainbow trout (Oncorhynchus mykiss) was ice-stored for 4 weeks and compared with unwashed/washed minces from unbled and bled trout in terms of rancid odour, peroxide value (PV), thiobarbituric acid reactive substances (TBARS) and redness loss. Muscle from saline-perfused fish, which had 72% less total haem, was deficient in rancid odour during the whole storage, while bled (54% less haem) and unbled samples developed rancid odour already after ~4 and 2 days; higher intensity without bleeding. PV/TBARS also developed in the order unbled > bled > perfused samples; however, PV/TBARS were not as completely prevented as rancid odour after perfusion. Saline washing (3 × 3 volumes) of unbled mince removed 84% haem and yielded the second most stable sample while saline washing (1 × 1 volumes) destabilised unbled mince, despite 64% haem removal. Concurrent antioxidant removal during washing of minces obviously counteracted the effect of blood removal and washing fish mince with small volumes of solution should be used with great care.     

铁死亡的机制及其在淋巴瘤中的研究进展

淋巴瘤是常见的血液系统恶性肿瘤，对人类健康造成极大的威胁。目前淋巴瘤的治疗方法包括化疗、分子靶向治疗、造血干细胞移植等，但耐药和复发难治仍是待解决的问题。铁死亡是新发现的一种细胞死亡模式，与铁依赖性的脂质过氧化损伤相关。靶向铁死亡为抑制淋巴瘤进展提供了新思路。本文从铁死亡的起始信号、中间事件、效应阶段、防御机制来阐述铁死亡的机制并回顾了铁死亡在淋巴瘤中的研究进展，为铁死亡在淋巴瘤治疗方法的应用方面提供新的思路。     

脂质氧化对肉制品中4 类有害物质形成影响的研究进展

肉制品加工过程中往往伴随着脂质氧化的发生，现有研究表明，脂质氧化能影响肉制品中杂环胺、N-亚硝基化合物、晚期糖基化终末产物及多环芳烃等有害物质的生成，这些物质的积累会降低肉制品的食用安全性并危害人体健康。本文综述了肉制品中脂质氧化的机制及氧化产物的反应活性、脂质氧化对肉制品中上述4 类有害物质形成的影响及相关控制措施，以期从控制脂质氧化的角度出发为肉制品安全性生产工艺提供参考。     

Development of a long‐life vacuum‐packaged ready‐to‐eat meat product based on a traditional Portuguese seasoned meat

Carne do alguidar is a Portuguese traditional pork fried meat, usually manufactured for self‐consumption purposes. This study developed a ready‐to‐eat (RTE) meat product, to meet today's consumers’ convenience, manufactured at the industrial scale evaluating its quality and shelf life, assessing the effect of vacuum packaging and the use of an antioxidant (50 ppm BHT) to enhance oxidative stability. Physicochemical and microbiological parameters were assessed, and a sensory analysis was performed. Interestingly, no significant differences were recorded between control (non‐BHT) and antioxidant (BHT) samples. Microbiological counts remained at low levels throughout the storage period, ensuring the product's required microbiological quality. At later storage stages, higher values of thiobarbituric acid‐reactive substances arose and off flavours and aromas were perceived. Still, overall appreciation was not affected until 12 months of storage and a significant depreciation was perceived only after 15 months. Fibrousness and rising of off flavours were negatively correlated with overall appreciation.     

Iron‐mediated lipid oxidation in 70% fish oil‐in‐water emulsions: effect of emulsifier type and pH

The objective of this study was to investigate the protective effect of five different emulsifiers on iron‐mediated lipid oxidation in 70% fish oil‐in‐water emulsions. The emulsifiers were either based on protein (whey protein isolate and sodium caseinate) or based on phospholipid (soy lecithin and two milk phospholipids with different phospholipid contents, MPL20 and MPL75). Lipid oxidation was studied at pH 4.5 and 7.0, and results were compared to lipid oxidation in neat fish oil. Results showed that all emulsions oxidised more than neat oil. Furthermore, emulsions prepared with proteins oxidised more at low pH than at high pH, and casein emulsions oxidised the least (Peroxide value (PV) at day 7 was 0.5–0.7 meq kg^?1). Among emulsions prepared with phospholipids, emulsions with MPL75 were the most oxidised followed by emulsions prepared with lecithin and MPL20. Thus, PV in MPL75 emulsions was 5.0–5.5 meq kg^?1 at day 7 compared with 0.9–1.9 meq kg^?1 in MPL20 emulsions.