植物油循环充氮工艺研究

油脂的氧化酸败速度与溶于油脂中的氧量有关,油脂的吸氧量可达其体积的15%~150%或质量的0.02%~0.2%,利用溶气泵的高强度气液混合特性,将99.99%的氮气在氮气压力0.05~0.15 MPa、流量5.0~150.0 L/min条件下,与植物油进行充分循环混合12~24 h,强行替换、排出油脂中吸收的氧气,以提高植物油的储存稳定性,并有效防止PET包装瓶的瘪瓶现象。     

Catalysis of Lipid Oxidation by Iron from an Insoluble Fraction of Beef Diaphragm Muscle

An insoluble fraction of beef diaphragm muscle was found to catalyze lipid oxidation in the presence of reducing compounds. Ascorbate (100 μM) catalyzed the formation of thiobarbituric acid reactive substances 3.3, 8.3 and 7.3-fold more effectively than cysteine, superoxide and NADPH, respectively. Ascorbate/insoluble fraction-catalyzed lipid oxidation was inhibited bv EDTA, ceruloolasmin, catalase and superoxide dismutase indicating the iivolvemknt of iron, hydrogen peroxide and superoxide anion. Both lipid oxidation and the release of iron from the insoluble fraction increased with increasing pH (5.0–7.0) in the presence of ascorbate. Iron bound to the insoluble components of beef muscle could be involved in catalysis of lipid oxidation.     

罗非鱼下脚料酶解液风味改善的研究

采用多酶复合酶解罗非鱼下脚料,考察不同添加剂和酶解时间对酶解液风味的影响。研究表明添加量分别为30、50 mg/kg的焦磷酸钠和茶多酚能够抑制酶解液中脂肪酸的氧化酸败而改善其脂肪酸败味。延长酶解时间至48 h,酶解液苦味值有所下降。对其总氨基酸以及游离氨基酸、可溶性蛋白和肽链疏水值(Q值)进行分析和感官鉴定。结果表明,48 h酶解液甜味氨基酸含量为1 178.05 mg/100 mL较36 h提高30%,而Q值为945.89 Cal/mol远小于1 300 Cal/mol,和感官分析结果一致。     

以糌粑为原料的华夫饼干货架期研究

为明确以糌粑为原料的华夫饼干的货架期,将华夫饼分别贮存于50和70℃条件下进行货架期加速实验,对华夫饼进行感官评价、质构测定和过氧化值测定,比较加速实验条件下华夫饼的货架期。并在此基础上,通过添加特丁基对苯二酚（Tertiary butylhydroquinone,TBHQ）比较其对防止糌粑华夫饼干氧化哈败的效果。结果发现,50℃加速条件下存放12 d后,糌粑华夫饼干的品质迅速下降,产品硬度下降49.53%,脆度下降58.02%,过氧化值上升0.84倍;70℃时品质下降更严重。综合过氧化值与感官评价,确定过氧化值达0.086 g/100 g时,华夫饼干开始出现明显哈败味,由此作为贮藏终点预测产品在常温（20℃）下的货架期仅为30 d。当原料中添加TBHQ后,华夫饼过氧化值增速放缓,说明TBHQ对糌粑饼干的氧化反应起到一定的阻止作用。经预测,添加0.2 g/kg TBHQ后糌粑华夫饼干的货架期（常温20℃）可达66 d。     

Furanoid fatty acids in oils from soybeans lacking lipoxygenase isoenzymes

The concentrations of 10, 13-epoxy-11, 12-dimethyloctadeca-10, 12-dienoic acid (F20) and 12,15-epoxy-13, 14-dimethyleicosa-12, 14-dienoic acid (F22) were determined by a stable isotope dilution assay in oils extracted from the soybean cultivar Century and from five soybean genotypes that lacked one or two of the three lipoxygenase isoenzymes. The concentrations of F20 and F22 ranged between 190–225 mg/kg oil and 91–132 mg/kg oil, respectively. The concentration differences were not correlated to the differences in lipoxygenase activities of the soybeans.     

Shelf-life dating of fish meats in terms of oxidative rancidity as measured by chemiluminescence

Chemiluminescence of fresh minced meats of six fish species was measured in order to examine the applicability of chemiluminescence in the prediction of shelf life. The chemiluminescence intensity of fresh fish meats was increased in proportion to the measuring temperature and differed significantly among fish meats. The shelf life of fish meats was estimated based on oxidative deterioration as measured by peroxide, carbonyl and thiobarbituric acid values, as well as sensory evaluation during storage of the fish meats at 0°C. It was observed that the shelf life of minced fish meats as judged by oxidative deterioration significantly correlated with chemiluminescence intensity of the fresh meats. The chemiluminescence method was shown to be very available for the prediction of the shelf life of fish meat.     

An investigation of rancidity inhibition during frozen storage of Wels catfish (Silurus glanis) fillets by previous ascorbic and citric acid treatment

The effect of preliminary ascorbic and citric acid (AA and CA, respectively) soaking treatments on the rancidity development in Wels catfish ( Silurus glanis ) fillets during further frozen storage (−18 °C; up to 6 months) was studied. Rancidity development was measured by biochemical quality indices (formation of free fatty acids, peroxides and secondary oxidation products) and compared with sensory analysis (appearance, rancid odour and consistency) and general chemical analyses (pH, expressible moisture and heme iron contents). When compared with control samples, AA- and CA-treated samples showed a lower ( P  < 0.05) formation of primary and secondary lipid oxidation compounds that was corroborated by a longer ( P  < 0.05) shelf-life time as a result of a lower rancid odour formation. According to these results, control samples showed a higher ( P  < 0.05) heme iron breakdown (months 3–6) and a lower ( P  < 0.05) water-holding capacity (higher expressible moisture value) (month 6).     

Effect of previous gutting on rancidity development in horse mackerel (Trachurus trachurus) during frozen storage at −20 °C

Gutting was applied to fresh horse mackerel (Trachurus trachurus) to study its effect on rancidity development during a prolonged frozen storage (up to 12 months at −20°C). To do so, chemical (free fatty acids, FFA; peroxide value, PV; thiobarbituric acid index, TBA-i; fluorescence ratio, FR) and sensory (odour and taste) analyses were carried out. The results showed that the gutting of horse mackerel led to a higher degree of oxidation in the frozen product, according to the chemical (PV, TBA-i and FR) and sensory (odour and taste) analyses. However, a lower extent of lipid hydrolysis (FFA formation) was detected at the end of the storage (twelfth month) as a result of gutting. It is concluded that the gutting of a medium-fat fish species such as horse mackerel is not recommended as previous treatment to frozen storage.