碳酸氢钠与酶制剂共用制备无铝油条

为了开发新型无铝酶制剂膨松剂以取代传统含铝膨松剂,研究了葡萄糖氧化酶(GOD)、戊聚糖酶、脂肪酶和真菌α-淀粉酶4种酶制剂与小苏打复配在油条中的应用。采用感官评分、计算体积膨胀率和质构分析的方法对油条的品质进行了评估。结果显示:在面粉中添加酶制剂能有效改善油条产品的品质;GOD、戊聚糖酶、脂肪酶和真菌α-淀粉酶与小苏打共用的最佳添加量分别是80μg/g、80μg/g、20μg/g和40～80μg/g。其中以添加了GOD的产品感官评分总分和体积膨胀率最佳,其质构特性的各项参数指标达到传统含铝膨松剂配方的产品水平。     

Effects of extracts of spices on rumen methanogenesis,enzyme activities and fermentation of feeds in vitro

BACKGROUND: An experiment was conducted to study the effects of boiling water, methanol and ethanol extracts (0, 0.25 and 0.50 mL) of seeds of Foeniculum vulgare (fennel), flower buds of Syzygium aromaticum (clove), bulbs of Allium sativum (garlic), bulbs of Allium cepa (onion) and roots of Zingiber officinalis (ginger) on rumen methanogenesis, fibrolytic enzyme activities and fermentation characteristics in vitro. RESULTS: Ethanol and methanol extracts of fennel, clove and garlic at 0.50 mL and clove at 0.25 mL inhibited (P < 0.05) methane production. Carboxymethylcellulase activity was reduced (P < 0.05) by ethanol and methanol extracts (0.50 mL) of fennel and clove (0.25 and 0.50 mL). The extracts of clove reduced (0.25 and 0.50 mL) xylanase and acetylesterase activities, and the fennel extract (0.50 mL) reduced (P < 0.05) xylanase activity. However, the extracts of garlic (0.50 mL) increased (P < 0.05) acetylesterase activity. Concentrations of volatile fatty acids were reduced (P < 0.05) by the extracts of garlic and onion. The extracts of garlic caused a decrease (P < 0.05) in acetate:propionate ratio (A:P) at 0.50 mL, whereas A:P was increased (P < 0.05) by the inclusion of 0.50 mL extracts of clove. Methanol and ethanol extracts of clove decreased (P < 0.05) in vitro organic matter degradability. Extracts (0.50 mL) of clove decreased (P < 0.05) the numbers of total protozoa, small entodiniomorphs and holotrichs, whereas extracts of onion, ginger and garlic enhanced (P < 0.05) protozoal numbers (both entodiniomorphs and holotrichs). CONCLUSION: Ethanol and methanol extracts of fennel and garlic have potential to inhibit rumen methanogenesis without adversely affecting rumen fermentation. Copyright © 2009 Society of Chemical Industry     

Effects of chitosan coating on oxidative stress in bruised Yali pears (Pyrus bretschneideri Rehd.)

The protective effects of chitosan on oxidative stress in bruised Yali pears (Pyrus bretschneideri Rehd.) were investigated. The fruit were treated with 1.5% chitosan before or after damage, respectively, and then stored at 16 °C and 90% relative humidity. Postharvest quality, reactive oxygen species (ROS) and antioxidant enzymes were analysed. Results showed that bruise induced the accumulation of H₂O₂ and O^2?. However, chitosan treatments reduced the levels of ROS and delayed the decease of glutathione (GSH) content in bruised fruit. Meanwhile, activities of antioxidant enzymes, including catalase, peroxidases, superoxide dismutase, ascorbate peroxidase or GSH reductase was 40.7%, 98.1%, 62.3%, 127.8% or 23.8% higher in chitosan‐bruised fruit and 41.1%, 80.8%, 18.5%, 102.9% or 45.2%, respectively, higher in bruised‐chitosan fruit than untreated bruised fruit on the 15th day.     

海藻酸钠明胶协同固定化酵母生产ATP

采用海藻酸钠与明胶协同固定化酵母合成ATP,考察了海藻酸钠、明胶浓度、酵母包埋量、交联剂浓度与交联时间等因素对固定化酵母胶体的机械强度、合成ATP转化率的影响,以及葡萄糖与牛血清蛋白向固定化酵母胶体内扩散的状况。结果表明,利用非稳态传递模型计算得到葡萄糖的有效扩散系数为5.82×10~(10)m~2/s,而BSA(V)不能扩散进入该固定化颗粒。进一步考察反应条件的影响,确定优化的反应条件为固定化酵母400 g/L.蔗糖80 g/L,KH_2PO_416 g/L,K_2HPO_4 92 g/L,MgSO_4 8 g/L,腺20 g/L,在该条件下得转化率平均在90%以上。     

碳源对固定化黑曲霉生产柠檬酸影响的研究

以海藻酸钙为载体包埋固定化黑曲霉AspergillusnigerW1-2细胞，用于生产柠檬酸，研究了碳源（蔗糖、葡萄糖和乳糖）及其浓度对固定化细胞生产柠檬酸的影响。结果表明，最适宜的碳源为蔗糖，其次为葡萄糖，固定化细胞利用乳糖时只生成少量柠檬酸。利用固定化细胞生产柠檬酸时，最适蔗糖浓度为120g／l，较利用游离细胞低（140g／L），并且，蔗糖浓度对固定化细胞生产柠檬酸的影响较利用游离细胞更为明显。     

Preservation of biological materials under desiccation

A number of life forms, including seeds, certain nematodes, bacterial and fungal spores, and cysts of certain crustaceans, show an ability to survive desiccation. The present article reviews the literature available on this subject and critically evaluates the evidence for various mechanisms that may be responsible for these phenomena. Specific mechanisms considered include vitrification (glass formation) by sugars and other polyhydroxy compounds that are accumulated by the desiccated structures, specific effects of polyhydroxy compounds on membranes, effect of “compatible solutes” on conformation of key proteins, as well as other biochemical mechanisms.

The article presents potential applications relevant to food technology and to biotechnology and reviews the research required to materialize more effective use of desiccation in food and biopreservation.     

Mechanism of preventive action of Viburnum dilatatum Thunb (gamazumi) crude extract on oxidative damage in rats subjected to stress

The fruit of Viburnum dilatatum Thunb (gamazumi) has been shown to prevent oxidative injury induced by water immersion restraint stress (WIRS) in rats. In this study the effect of gamazumi crude extract (GCE) on antioxidant enzymatic activities in the plasma, liver and stomach of rats with WIRS was investigated to elucidate the mechanism of prevention of oxidative injury. Ulcer formation and lipid peroxidation were inhibited in rats supplied GCE for 2 weeks in comparison with rats supplied water. Although the activities of plasma, hepatic and gastric antioxidant enzymes in rats given water were decreased by WIRS, only slight changes were observed in rats given GCE. There was no difference in enzymatic activities between the water and GCE groups not subjected to WIRS. Furthermore, ferrous ascorbate‐induced oxidation in hepatic homogenate from rats given GCE was inhibited. These results suggest that ingestion of GCE does not induce antioxidant enzymes and that the absorbed antioxidant components of GCE have a direct effect on oxidative injury in the body. Copyright © 2003 Society of Chemical Industry     

磷酸根离子对固定化酵母细胞传质效果改善的研究

利用磷酸根离子对海藻酸钙凝胶有软化、破坏作用的原理,来处理用海藻酸钠-PVA混合载体包埋制得的固定化细胞颗粒,可有效降低凝胶结构的紧密程度,增强其通透性,获得较好的传质效果,通过扫描电镜对凝胶颗粒结构的袁征证实了实验效果。实验得出最好的磷酸根离子处理方式为：用0．8mol／L KH2PO4浸泡固定化细胞颗粒24h后再进行发酵生产。最后用多批次发酵实验验证了用磷酸根离子处理后的固定化酵母细胞的产酒、机械性能的稳定性。     

果寡糖对肥育猪生长及肠道菌群等的影响

本试验研究了饲粮中添加果寡糖对"杜长加”肥育猪生长及肠道菌群和消化酶活性的影响.与对照组相比,肥育猪日粮中添加0.50%和0.75%果寡糖使日增重分别提高了9.67%(P＜0.01)和10.67%(P＜0.01),使料重比分别降低了8.19%(P＜0.01)和7.60%(P＜0.05);添加0.50%和0.75%果寡糖使结肠中双歧杆菌、乳酸杆菌数分别增加了299.49%(P＜0.01)和314.81%(P＜0.01),97.40%(P＜0.05)和141.67%(P＜0.05),并使结肠内容物pH值分别降低了0.50(P＜0.05)和0.90个单位(P＜0.01).添加果寡糖使结肠中大肠杆菌数、梭菌数下降,十二指肠内容物中总蛋白水解酶、胰蛋白酶、淀粉酶活性提高,果寡糖对胰脏中消化酶活性的影响不显著.     

Bifidobacterium carbohydrases-their role in breakdown and synthesis of (potential) prebiotics

There is an increasing interest to positively influence the human intestinal microbiota through the diet by the use of prebiotics and/or probiotics. It is anticipated that this will balance the microbial composition in the gastrointestinal tract in favor of health promoting genera such as Bifidobacterium and Lactobacillus. Carbohydrates like non-digestible oligosaccharides are potential prebiotics. To understand how these bacteria can grow on these carbon sources, knowledge of the carbohydrate-modifying enzymes is needed. Little is known about the carbohydrate-modifying enzymes of bifidobacteria. The genome sequence of Bifidobacterium adolescentis and Bifidobacterium longum biotype longum has been completed and it was observed that for B. longum biotype longum more than 8% of the annotated genes were involved in carbohydrate metabolism. In addition more sequence data of individual carbohydrases from other Bifidobacterium spp. became available. Besides the degradation of (potential) prebiotics by bifidobacterial glycoside hydrolases, we will focus in this review on the possibilities to produce new classes of non-digestible oligosaccharides by showing the presence and (transglycosylation) activity of the most important carbohydrate modifying enzymes in bifidobacteria. Approaches to use and improve carbohydrate-modifying enzymes in prebiotic design will be discussed.