利用SDS-PAGE法检测火腿肠中大豆蛋白的含量

利用SDS-聚丙烯酰胺凝胶电泳(SDS-PAGE)结合凝胶成像来分析测定火腿肠中大豆分离蛋白的含量.试验得出电泳分离肉制品中大豆分离蛋白的优化条件为:浓缩胶为5%、分离胶为12%、上样量为20μL、初始电压为80 V,进入分离胶层后电压100 V.大豆蛋白含量在0~6%范围内与其酸性A3亚基线性相关,回归方程为Y=2.760 9X-0.383 8,相关系数为0.994 1.     

Venom variation and chemoreception of the viperid Agkistrodon contortrix: evidence for adaptation?

Previous studies of chemoreceptive behavior in vipers suggest that snakes focus on the scent of envenomated tissue to track their prey following envenomation. Other studies have indicated a correlation between qualitative differences in venom biochemistry and geographic variation in diet. The North American copperhead (Agkistrodon contortrix) varies geographically in diet and venom biochemistry; snakes were collected from three populations (Kansas, Texas, and Louisiana) that are known to have different prey preferences. Behavioral experiments were conducted to assess whether copperheads preferred envenomated prey more than nonenvenomated prey, as do other species of vipers studied thus far. Additional experiments tested the ability of copperheads to distinguish between envenomated prey from different geographic populations, and between geographic populations of copperheads and two other species of viper. Results indicated that copperheads prefer envenomated prey to nonenvenomated prey. In envenomated-prey discrimination experiments, copperheads distinguished between envenomated prey from different geographic populations, and some snakes distinguished envenomated prey of A. contortrix from those of A. piscivorus and Sistrurus catenatus. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to study the variation of venom biochemistry in this species and two other taxa (A. piscivorus and S. catenatus), and confirmed intraspecific and interspecific variation of venom proteins. Relative potency of the venom from different populations as indicated by time to immobilization experiments was in the order: Louisiana >Texas > Kansas. The relative potency of the venom from each population matched the order of preference in the chemoreception experiments. These results suggest that chemoreception is sensitive to subtle differences in venom biochemistry and may reflect adaptation to improve efficiency of finding envenomated prey.     

Influence of processing conditions on the physicochemical and sensory properties of sesame milk: A novel nutritional beverage

Production of sesame milk is one of the methods for increasing consumption of sesame as an excellent nutritional resource. The aim of this study was to examine the effects of sodium bicarbonate concentration in soaking water (0, 0.5 and 1 g/100 mL NaHCO₃), roasting temperature (0 and 145 °C) and blanching time (0, 15 and 30 min) on physicochemical and sensory properties of sesame milk. Changes promoted by these processing conditions were also evaluated via color analysis and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The processing parameters mainly affected pH, total solids, protein, fat, ash, lipoxygenase activity, stability, specific gravity, viscosity, color features and sensory properties. Sensory evaluation revealed that overall acceptability was higher in all treatments than the control. SDS-PAGE analysis showed that 7S globulins decreased by roasting and soaking while 11S globulins of sesame milk proteins increased by roasting. The optimum processing conditions were found to be soaking in water containing 0.5 g/100 mL NaHCO₃, blanching for 15 min and without any roasting when desirability function method was applied.     

Evaluation of the rheological,textural, microstructural and sensory properties of soy cheese spreads

In this work, different processes including lactic acid bacteria fermentation, glucono-δ-lactone (GDL) coagulation and enzymatic hydrolysis were applied to produce soy cheese spread without any milk solid and/or alkaline metal caseinates added. All the soy cheese spread samples were studied with respect to the differences in the textural properties – utilizing TPA and rheological behavior, besides their microstructural features and sensory assessment. In addition, urea–SDS-PAGE assay was used to investigate the proteolysis in enzymatic hydrolysis process. As a result, the soy cheese spread sample produced by the combined use of GDL and lactic acid bacteria fermentation together with enzymatic hydrolysis process, was observed with better spread-ability, more acceptable sensory features, and stable homogeneous structure than other samples.     

Species identification of snapper: A food poisoning incident in Taiwan

A snapper (Lutjanidae fish) is a carnivorous coral reef fish that is distributed in sea areas around Taiwan. In December 2008 in southern Taiwan, a food poisoning incident occurred due to the ingestion of snapper, and the causative residue of ciguatera was investigated using a toxicity assay. To identify the species of the causative sample, six suspected species of Lutjanidae fish commonly found in Taiwan were analyzed using both sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) techniques. According to the low molecular weight region (<30.0 kD) of species-specific patterns extracted from myofibrillar and sarcoplasmic proteins, the 6 snapper species could be clearly differentiated by the SDS-PAGE method. Furthermore, a consistent 465 bp sequence of the mitochondrial cytochrome b gene from the 6 snapper species was amplified by the PCR method and was rapidly distinguished by the analysis of restriction enzymes. According to both SDS-PAGE and PCR-RFLP methods, the poisonous sample was identified as Lutjanus bohar, which is also a notorious Lutjanidae species containing ciguateric toxins.     

SDS-PAGE法分离和表征明胶中不同构象

仔细分析已发表的文献表明,迄今为止用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)测定明胶分子量分布仅限于分出<α、α_1、α_2、和β组份,而γ及>γ的组份未能检出,也就是说,分子量大约30万以上的组份未能进入凝胶板内(以下简称“入板”)。这对明胶构象的全分析和对明胶质量的判断都是一个严重的缺陷。本文主要探讨和研究了γ及>γ组份的入板问题。所采取的办法有:有效地控制丙烯酰胺和甲叉双丙烯酰胺(交联剂)的相对含量,选择合适的交联度梯度和孔径大小,使之既适用于α和β组份迁移,也能让γ及>γ的组份入板。此外,在小交联度和大孔径情况下,还能符合凝胶板对凝胶强度的基本要求。实验结果表时,操作过程缩短,分辨率改善,成功地得到了从几万到30万以上的分子量分布的明胶全部构象的图谱。     

Some functional properties of oat bran protein concentrate modified by trypsin

Oat bran protein concentrate (OBPC) was prepared from oat bran, and hydrolyzed using trypsin. Protein hydrolysates of three different degrees of hydrolysis (4.1%, 6.4% and 8.3% respectively) were obtained. SDS-PAGE analysis demonstrated that oat globulin was the major protein component in OBPC. After trypsin treatment, acidic polypeptides were partly degraded into large peptides (M_r = 29,000–33,000) and small peptides (M_r < 20,000); however, basic polypeptides were almost intact. The functional properties of the resulting products were compared with those of control OBPC. Marked changes in the protein functionality were caused by proteolysis. The solubility, water-holding capacity, emulsifying activity and foaming ability of the hydrolysates gradually increased with the increase in DH. However, the oil-holding capacity, emulsifying stability and foaming stability of the hydrolysates reduced to a certain extent.     

大豆粕蛋白酶酶解条件和产物分析研究

以水解度为衡量指标,通过正交试验设计,对木瓜蛋白酶、胰蛋白酶和As1.398蛋白酶酶解大豆粕的最佳水解条件进行了筛选.试验结果表明:木瓜蛋白酶水解大豆粕的最佳条件为pH7.0、温度60℃、时间5 h、酶浓度5%.胰蛋白酶水解大豆粕的最佳条件为pH7.0、温度50℃、时间7 h、酶浓度5%;As1.398蛋白酶水解大豆粕的最佳条件为pH6.5、温度50℃、时间7 h、酶浓度5%.对酶解产物进行超滤和SDS-PAGE电泳分析表明,因酶解条件不同,大豆粕酶解产物中蛋白质和肽的组成及其数量也不同;酶的种类不同,大豆粕酶解产物组成也不同;大豆粕水解度越高,其酶解产物中小分子肽数量越多.     

Inactivation of polyphenol oxidase from Pacific white shrimp by dense phase carbon dioxide

The inactivation of polyphenol oxidase (PPO) from Pacific white shrimp exposed to dense phase carbon dioxide (DPCD) treatment was investigated. PPO activity showed a dramatic loss at 4–25 MPa and 37 °C. At the lower pressure (4–15 MPa), the experimental data of inactivation followed the first-order reaction kinetic model, the pressure sensitivity (Z_P) of the kinetic parameters was 49.02 MPa and the activation volume (△ V^≠) was − 120.88 cm³/mol. At the higher pressure (20 and 25 MPa), the experimental data of inactivation followed the biexponential kinetic model. The kinetic rate constant k_F and k_S of fast and stable fractions were 2.45 and 0.08 min^{− 1}, respectively. The decimal reduction time D_F and D_S were 0.94 and 29.43 min at 25 MPa and 37 °C, respectively. After DPCD treatment, the loss activity of PPO had no restoration storing for 6 days at 4 °C. The results of SDS-PAGE and activity staining also showed that DPCD treatment had the obvious inhibitory effect on PPO from Pacific white shrimp. The PPO activity in vivo was easier to be inactivated than that in crude PPO extracts under the same DPCD treatment conditions.

Industrial relevance

There is a growing interest in non-thermal pasteurization methods, which could retain food's freshlike physical, nutritional, and sensory qualities. Pacific white shrimp accounts for 90% of the global aquaculture shrimp production, they are becoming increasingly popular. However, enzymatic browning of shrimp has been of great concern to food scientists and food processors. Dense phase carbon dioxide (DPCD) may be an adequate tool to obtain high quality since PPO activity could not be inactivated totally by high pressure under 400 MPa yet. The present work deals with the inactivation of PPO from Pacific white shrimp exposed to DPCD treatment in order to explore the feasibility of shrimp by DPCD process.