A novel compound, 7,10-dihydroxy-8(E)-octadecenoic acid from oleic acid by bioconversion

Sixty-two cultures from the Agricultural Research Service (ARS) Culture Collection and 10 cultures isolated from soil and water samples in Illinois were screened for their ability to convert agricultural oils to value-added industrial chemicals. A new compound, 7,10-dihydroxy-8(E)-octadecenoic acid (DOD), was produced from oleic acid at a yield of greater than 60% by bacterial strain PR3 which was isolated from a water sample in Morton, IL. To our knowledge, DOD has not been previously reported. The optimum time, pH and temperature for the production of DOD were 2 days, 7.0, and 30°C, respectively. The production of DOD is unique in that it involves hydroxylation at two positions and rearrangement of the double bond of the substrate molecule.     

黄酒及其酸败组分的高效毛细管电泳检测方法的研究

黄酒生产与陈化过程中发生酸败变质,是黄酒业面临的头等难题。本文中以黄酒原酒为对象,从检测波长、缓冲液组成、分离电压等方面对高效毛细管区带电泳法检测黄酒组分的条件进行研究。结果表明,选择检测波长215nm、0.075nmol/L的pH=10.0的磷酸氢二钠-四硼酸钠缓冲液、分离电压8kV检测,可以得到理想的黄酒原酒、黄酒料酒与酸败黄酒原酒的高效毛细管区带电泳图谱。通过对比分析,确定导致酸败的可能组分峰位于保留时间27.0³1.0min区段。研究结果为黄酒酸败组分的检出、质量标准构建及黄酒生产过程中的质量控制奠定基础,具有一定的应用价值。      

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。     

Physicochemical Properties of Surimi Seafood as Affected by Electron Beam and Heat

Physicochemical changes of surimi seafood under electron beam (e‐beam) and heat were investigated. Heat caused color browning and texture softening. E‐beam (up to 4 kGy) deteriorated neither color nor texture when the sample temperatures were between 5 and 23°C. However, firmer texture was measured when samples were treated by e‐beam while frozen. None of the treatments changed rancidity of surimi seafood within the parameters tested. Heat, as compared with e‐beam, generated the same headspace volatiles, however, to a greater extent. E‐beam was determined to be an excellent pasteurization alternative for surimi seafood in terms of retention of fresh‐like physicochemical attributes.     

Influence of γ-irradiation and ice storage on fat oxidation in three Indian fish

The influence of low-dose γ-irradiation (up to 5 kGy) on fat oxidation in skin and flesh fractions of some commercially important fishes (Indian mackerel, white pomfret and seer) during ice storage was examined. Thiobarbituric acid (TBA) values increased in both control and irradiated fish particularly in mackerel and seer meat. In mackerel, the TBA values declined towards later part of storage. Pomfret skin, but not mackerel and seer skin, showed radiation-induced oxidation, which increased further during ice storage.     

Natural Products Inhibit Oxidative Rancidity in Salted Cooked Ground Fish

The extent of lipid oxidation in salted cooked ground fish treated with several natural products (polyphenols, dried spices and fresh spices) was measured by the production of thiobarbituric acid reactive sub-stances (TBARS). The fresh spices, ginger and tumeric, were more potent than garlic and onion (at 10% conc) in inhibiting lipid oxidation in salted cooked ground fish. The order of antioxidative potency of the dried spices was: cloves > cinnamon > cumin ～ black pepper > fennel ～ foenugreek. The dried spices were more effective antiox-idants than fresh spices. The polyphenols were the most potent group of natural antioxidants. The order of potency of the polyphenols (0.01% concentration) was: ellagic acid > tannic acid > myricetin > quercetin.     

去皮椒盐油炸花生货架寿命的研究

通过对去皮椒盐油炸花生的加速氧化试验，建立了计算其在任一贮藏温度下货架寿命的回归方程。此外，还对包装工艺和包装材料同货架寿命之间的关系作了探讨。     

High-pressure effects on lipid oxidation

Rendered pork fat (0.44 water activity, A_w) was subjected to high-pressure treatment of 800 MPa for 20 min at 19°C prior to storage at 4, 25, and 50°C. In all cases, high pressure-treated samples oxidized more rapidly (had a shorter induction period) as shown by the peroxide value (PV), 2-thiobarbituric acid value, and ultraviolet absorbance. The effect was less marked at lower pressures. In contrast, at all water activities outside the range of 0.40–0.55, the PV of the high pressure-treated pork fat was lower than control samples stored similarly, and the PV of rancid fat decreased slightly on pressure treatment at 19°C, but not at higher temperatures. This effect may explain the observed inhibition of oxidation at most water activities. At 0.40–0.55 A_w, other factors, such as the liberation of transition metals, may override the destruction of peroxides.     

Solubility and viscosity of herring (Clupea harengus) proteins as affected by freezing and frozen storage

ABSTRACT:  The aim of this work was to evaluate the effects of freezing and frozen storage at –24 °C on the quality of Icelandic herring fillets, focusing on protein solubility and viscosity at pH 2.7 and 11 used for pH-aided protein isolation. The evaluation of quality was based on chemical analyses, protein degradation measurements, and changes in protein solubility and viscosity at pH 2.7 and 11 after up to 6-mo frozen storage of the herring fillets. Lipid oxidation measured as TBARS values increased significantly during the frozen storage ( P < 0.05). Protein solubility at pH 2.7 decreased during frozen storage for 6 mo, where the solubility was about 10% lower after 6-mo frozen storage compared to the beginning ( P < 0.05). At pH 11, the solubility became approximately 15% lower after 6-mo frozen storage compared to initial solubility ( P < 0.05). Viscosity, measured at pH 2.7, increased after 3 mo of frozen storage ( P < 0.05). At pH 11, the viscosity increased significantly after 1-wk frozen storage, compared to fresh herring fillets, but did not increase significantly with further storage ( P < 0.05). Changes found in solubility and viscosity indicated protein degradation due to freezing and frozen storage. SDS-PAGE analysis did not reveal any protein cross-linking or aggregation formation, either with frozen storage or due to exposure to low pH.     

Antioxidant activity of lipid-soluble phenolic diterpenes from rosemary

A high-performance liquid chromatography method for analyzing the phenolic diterpenes present in rosemary (Rosmarinus officinalis L.) and commercial rosemary extracts is reported. Carnosic acid was the major phenolic diterpene present in rosemary leaves, with lesser amounts of 12-methoxycarnosic acid and carnosol. Several commercial rosemary extracts also were analyzed by this method, and in addition to these three compounds other phenolic diterpenes, such as 7-methoxyrosmanol, 7-methoxy-epirosmanol, and rosmanol, were found in some samples. These latter three compounds seem to be artifacts, produced from carnosic acid by oxidation and cyclization. The major phenolic diterpenes were isolated, and their relative antioxidatn activities in soybean oil were measured by the Rancimat. The potency of carnosic acid was more than twice that of any other compound. The antioxidant activity of pure carnosic acid was compared to butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), and tertiary butylhydroquinone (TBHQ) and was several times greater than BHT and BHA but less than TBHQ. Nuclear magnetic resonance data for several of the compounds that were incompletely characterized in previous literature are reported.