核桃仁的酸败及抑制

针对核桃仁在储藏过程容易出现酸败变质的现象,对核桃仁酸败机理及其评价指标进行了分析.并对如何有效的抑制核桃仁酸败提出了一些解决方法,以便于人们对核桃仁的酸败进行控制.     

Color and Oxidative Rancidity of Gamma and Electron Beam-Irradiated Boneless Pork Chops

Color and oxidative rancidity were determined for chilled (3 ± 2°C) and frozen (?17 ± 3°C) boneless pork chops packaged in vacuum or air and irradiated to an absorbed dose of 0, 1.5 or 2.5 kGy (chilled) or 0, 2.5 or 3.85 kGy (frozen) of electron beam or cobalt⁶⁰ irradiation. Irradiation of vacuum-packaged chops produced redder, more stable (color and rancidity) product. More pronounced oxidative rancidity and less stable display color were noted for samples irradiated in aerobic packaging. Irradiation source had varying but limited effects on color and rancidity. Optimum packaging conditions can control color and rancidity changes in boneless chops, thereby enabling irradiation to be a useful intervention technology.     

关于罐装蛋白质粉产生异味的研究

目的利用正交试验结合气相色谱、质谱技术探究罐装蛋白质粉产生异常气味问题的原因及预防措施。方法利用顶空气质联用仪检测在不同温度、湿度下存放不同时间的罐装蛋白质粉中存在的挥发性呈味物质,从而查找出导致蛋白质粉产生异味的来源;利用气相色谱仪测定罐装蛋白质粉中脂肪酸的含量,从而查找蛋白质粉产生异味的原因。结果罐装蛋白质粉在一定条件下保持较高的湿度和温度,其存放时间越长,越容易产生挥发性呈味物质,而产生异味的罐装蛋白质粉的脂肪酸含量相对正常蛋白质粉较低。结论罐装蛋白质粉在高湿高温诱发下,其含有的脂肪酸容易与分子氧发生反应,导致酸败,生成一系列不良气味物质;控制好蛋白质粉的温度、湿度等保存条件可以有效地预防蛋白质粉中的脂肪酸酸败问题,从而保证蛋白质粉的营养价值。     

The effect of different paprika types on the ripening process and quality of dry sausages

The main objective of the study was to evaluate the effects of large amounts of paprika and different amounts of hot paprika on the ripening process of dry sausage. The sausages, called ‘chorizo’ were evaluated for changes in texture, colour and physico‐chemical parameters, including rancidity. The results show that when either paprika contents or concentrations of hot paprika were increased, compared with a control, the ripening process of dry sausages was accelerated, probably by the promotion of lactic acid bacteria growth, which, in turn, lead to a fast drop in pH and water activity. These effects cause a rapid development of texture when compared with a suitable control, with an optimal hardness being reached in less time. These products have greater colour intensity, which remains more stable, together with lower malonaldehyde contents than controls. It was shown that paprika, especially the hot variety, exerts a protective effect against rancidity.     

Effects of seed damage on the oxidative stability of poppy seed oil

This study was conducted to assess the reduction of life time and quality of poppy seeds considering a mechanical damage, which may occur during harvesting. Vienna, Vienna, Austria Poppy seeds were crushed to receive 90%, 80%, 70%, 60% and 50% intact seeds, the undamaged 100% intact seeds served as controls. The samples were stored at 40 °C for 175 d and oxidation experiments performed periodically by assessing conjugated dienes, p‐anisidine reactive products, the iodine value, the acid value and γ‐tocopherol content. With increasing degree of mechanical damage the shelf life declined, the oxidation products were formed more rapidly and the main antioxidant in poppy seeds γ‐tocopherol was consumed. Considering the reduction of life time by including all quality parameters the shelf life of the 10% damaged seeds was reduced by 50.5%. This reduction was reached up to 82% for the 50% damaged seeds compared to the control. A high correlation was found between the increase in oxidation products and the degradation of γ‐tocopherol. This study show that increased damage during harvesting (10‐50%) is responsible for a faster loss of product quality especially in seeds containing high amounts of polyunsaturated fatty acids like poppy seeds.     

Stability of Washed Frozen Mince from Channel Catfish Frames

ABSTRACT: Sodium citrate, sodium erythorbate, sodium citrate plus sodium erythorbate, sodium citrate plus sodium erythorbate, and polyphosphate were used in washed and unwashed channel catfish mince. Washing reduced (P 0.05) lipids and increased (P 0.05) Hunter 'L'value (lightness) of mince. Thiobarbituric reactive substances and free fatty-acid changes during frozen storage were reduced in the washed mince. Addition of antioxidants did not significantly improve the overall quality and shelf-life of the frozen mince. Washing did not have an effect on the fatty-acid composition of neutral and phospholipids in the mince.     

黄酒发酵过程中酸败现象的研究

黄酒发酵过程中经常会出现酸败的现象,发酵醪的特征是其中乳酸含量超标,原因是乳酸杆菌的非正常代谢造成的。对发酵醪镜检可以有效判断发酵是否正常。创造良好的工艺条件,确保酵母菌、乳酸菌等菌群平衡,保持糖化发酵平衡,是防治酸败的根本方法。     

Chemiluminescence as a method for oxidative rancidity assessment in autoxidized marine oils

Chemiluminescence based on light emission from excited oxygen species,e.g. singlet oxygen and triplet carbonyls, has been used to measure the oxidative rencidity of fish oils. The luminescence was recorded after sodium hypochlorite addition to the oils dissolved intert-butanol. In addition to high sensitivity and ability to detect small changes in rancidity, the method is fast and may be used as a supplement to the standard chemical methods for quality assessment and antioxidant evaluation. However, care has to be taken in interpretation of the chemiluminescence data of different fish oils, as the light emission depends on both the composition and the rancidity level of the oil. The autoxidized oils were also characterized by peroxide value, thiobarbituric acid value, anisidine value, Kreis rancidity index, iodine value, ultraviolet measurements, capillary gas chromatography, size-exclusion chromatography and sensoric evaluation.     

Volatile off-flavour compounds in desiccated coconut

Aliphatic methyl ketones and secondary alcohols have been isolated from desiccated coconut and shown to be responsible for the rancid off-flavour. Two series of compounds have been isolated. The series with an odd number of carbon atoms (C_5,7,9,11) comprising pentan-2-one, pentan-2-ol, heptan-2-one, heptan-2-ol, nonan-2-one, nonan-2-ol and undecan-2-one is derived from even chain fatty acids one carbon atom longer, present in the coconut oil by a modified β-oxidation due to growth of moulds. Heptan-2-one and nonan-2-one were present in the greatest concentration in the rancid coconut. These compounds gave an odour reminiscent of rancid almonds and turpentine respectively while heptan-2-ol and nonan-2-ol gave an odour similar to rancid coconut as well as a musty, stale odour. This type of off-flavour has been called ketonic rancidity and is an oxidative variation of the hydrolytic type of rancidity. The presence and origin of the even numbered series (C_6,8), hexan-2-one, hexan-2-ol and octan-2-one is discussed. The increase in C_5,6,7,8,9,11 oxidation products in the rancid samples occurred at the expense of C_8,10,12 short chain fatty acids.