采用β-环状糊精包埋法去除稀奶油中的胆固醇

研究了不同条件下稀奶油中胆固醇去除率和 β 环状糊精残留率的变化情况。试验结果表明 ,稀奶油经 2 0MPa均质后 ,添加 8 5 % β 环状糊精 ,经 3 0℃混合 1 0min ,4℃静置 1 0min ,40 0 0r/min离心 1 0min处理 ,胆固醇去除率能够达到 84 2 1 % ,β 环状糊精残留率为 1 3 1 3 %。     

Isolation and Molecular Characterization of Multidrug-Resistant Strains of Escherichia coli and Salmonella from Retail Chicken Meat in Japan

ABSTRACT: Sixty‐nine Escherichia coli and 10 Salmonella isolates, recovered from retail chicken meat in Hiroshima prefecture, Japan, were assayed for antimicrobial susceptibility, the presence of integrons and antimicrobial resistance genes. Twenty‐eight out of 69 (40.6%) of E. coli and all 10 Salmonella isolates were exhibited multidrug resistance phenotypes. The most commonly reported resistance phenotypes were against ampicillin, streptomycin, spectinomycin, kanamycin, tetracycline, and trimethoprim/sulfamethoxazole. PCR screening for integrons showed that 8 (11.6%) of the E. coli isolates were positive for the class 1 integrons and 1 isolate (1.4%) was positive for the class 2 integrons. Among the 10 Salmonella isolates, 9 were positive for class 1 integrons and none was positive for class 2 integrons. The identified antibiotic resistance gene cassettes within the class 1 integrons were dfrA1, dfrA7, aadA1, aadB, and catB3, while dfrA1, sat2, and aadA1 were identified within class 2 integron. The β‐lactamase resistance gene bla_TEM‐1 was identified in 12 (17.3%) of E. coli isolates and in only one of the Salmonella isolates. The bla_CMY‐2 gene, encoding AmpC β‐lactamase, was detected in 16 (23.2%) of the E. coli isolates only. Conjugation experiments demonstrated that there was plasmid‐mediated transfer of bla_CMY‐2 and bla_TEM‐1. These results highlighted the role of retail chicken meat as a potential source for multidrug‐resistant strains of E. coli and Salmonella. To the best of our knowledge, this is the 1st report of isolation and molecular characterization of multidrug‐resistant strains of E. coli from retail chicken meat in Japan.     

Caustic-induced gelation of β-lactoglobulin

The gelation kinetics of β-lactoglobulin (βLg) solutions has been determined in the alkaline regime over a wide range of protein concentrations, gelling temperatures and gelation pH (pH_gel), set using NaOH. The behaviour is compared with caustic-induced gelation of whey protein concentrate and the alkaline dissolution of heat-induced whey gels. The gelation time decreases significantly between neutral conditions and pH_gel 9, because of the activation of the free cysteine groups and displacement to the monomeric form, and between pH_gel 10 and 11, due to the base denaturation of βLg. Both transitions are associated with a significant decrease in the activation energy of gelation. At pH_gel >11.5 the gelation time is observed to increase with pH_gel, owing to destruction of interprotein crosslinks. These results are consistent with the recently reported observation that a minimum pH for the dissolution of βLg gels and aggregates exists around 11.6 [ Biomacromolecules 8 (2007) 1162]. This phenomenon has been assigned to the destruction of non-covalent interactions that would inhibit the final percolation of the gel.     

Flavour retention during high temperature short time extrusion cooking process: a review

Research on the stability of flavours during high temperature extrusion cooking is reviewed. The important factors that affect flavour and aroma retention during the process of extrusion are illustrated. A substantial number of flavour volatiles which are incorporated prior to extrusion are normally lost during expansion, this is because of steam distillation. Therefore, a general practice has been to introduce a flavour mix after the extrusion process. This extra operation requires a binding agent (normally oil), and may also result in a non-uniform distribution of the flavour and low oxidative stability of the flavours exposed on the surface. Therefore, the importance of encapsulated flavours, particularly the β-cyclodextrin-flavour complex, is highlighted in this paper.     

Optimizing Cholesterol Removal in Cream Using β-Cyclodextrin and Response Surface Methodology

Average cholesterol reduction increased as β-cyclodextrin concentration increased, regardless of other factors. The process was optimized using RSM. When β-cyclodextrin addition was 10%, the effect of stirring speed was more noticeable than that of stirring time. When stirring speed was at 1,600 rpm, 94.2% of cholesterol was reduced in 30 min. When stirring time was 20 min, the cholesterol was reduced 97.99% using 15%β-cyclodextrin. When stirring speed was 1,200 rpm, the effect of β-cyclodextrin addition was greater than that of stirring time. Although the percentage of cholesterol reduction varied with different factors and conditions, about 94% of cholesterol was removed from cream.     

β-Lactoglobulin – a three-dimensional perspective

Summary Bovine β-lactoglobulin has been the subject of intense study over the past 60 years by, effectively, every available physicochemical technique, of which one of the most powerful is X-ray crystallography. We present a short review of the X-ray crystallographic work on milk protein together with an overview of the properties as they are seen from the current state of crystallographic analyses. At the present time, structural analyses do not provide any further insights into the possible function of the protein.     

Cholesterol Reduction in Liquid Egg Yolk using β-Cyclodextrin

A process to reduce cholesterol in liquid egg yolk using β-cyclodextrin (CD) was optimized by response surface methodology, based on cholesterol reduction and yield. The most important factors influencing cholesterol reduction were dilution of egg yolk to a defined water:solid ratio and CD concentration. In the final process, egg yolk was adjusted to pH 10.5, diluted to a water:solid ratio of 2.9, heated to 50°C, and CD added at a CD:cholesterol molar ratio of 4.0. The slurry was mixed for 6.5 min at 1800 rpm, cooled to 4°C and centrifuged. Cholesterol in the supernatant was reduced by 89.2%. The yield, cholesterol and CD in the final product were adjusted by varying centrifugal force and CD concentration.     

响应面法优化β-环糊精脱除鸭蛋黄油脂胆固醇工艺条件

为了获得β-环糊精脱除鸭蛋黄油脂胆固醇的最佳工艺条件,选用五因素五水平的中心组合设计,以水油比(W:O)、β-环糊精与油之比(β-CD:O)、时间、温度、搅拌速度为影响因素,以胆固醇脱除率、蛋黄油脂回收率为响应值,建立了回归模型。结果表明:温度、W:O与时间、时间与搅拌速度的交互效应对两响应值都有显著影响(P0.01);W:O与β-CD:O、W:O与温度、时间与温度的交互效应虽对胆固醇脱除率影响不显著(P0.05),但对油脂回收率有显著影响(P0.01)。利用渴求函数的响应曲面图、等高线图优化两响应,确定了最佳工艺条件:W:O=1.45(V/m),β-CD:O=0.30(m/m),时间21.83 min,温度10℃,搅拌速度975.83 r/min。在此条件下,预测的渴求值为0.752,胆固醇脱除率为72.48%,油脂回收率为68.05%,并验证了回归模型的有效性。     

The characterization of soybean varieties by fluorescence spectroscopy

Fluorescence spectroscopy was used to differentiate between β‐conglycinin (βC) and glycinin (G) fractions that were isolated from four food grade soybean varieties (Glycine max var. K1430, Hutcheson, K93‐90‐29, and KS4997) grown in the same location. The protein fractions were discriminated by using spectroscopic tryptophan fluorescence emission and synchronous scanning techniques that took advantage of the sensitivity of the chromophore to changes in the protein environment. The relative intensities of the βC and glycinin fluorescence ranged from 1.00 to 1.30 and 1.00 to 1.31 respectively. The intensities of the βC and glycinin synchronous fluorescence ranged from 1.00 to 1.45 and 1.00 to 1.30 respectively. The spectroscopic method proved to be an effective technique to differentiate between different soybean varieties.     

Selective Solubilization of α- Lactalbumin and β-Lactoglobulin into Reversed Micelles from Their Mixtures

Phase transfer experiments were performed, involving contact between an aqueous 1:1 solution of α-lactalbumin and β-lactoglobulin and an AOT-in-isooctane reversed micellar phase. The resulting extraction and separation of the two proteins were analyzed as functions of pH, ionic strength and total protein concentration using SDS-PAGE, and compared with extractions from pure solutions. At low protein concentrations, the extent of reversed micellar solubilization of the two pure proteins predicted well the extraction from mixtures. However, at higher protein concentrations β-lactoglobulin appeared to be excluded from the micellar droplets. Because of the significantly different partitioning behavior of the two proteins, reversed micellar extraction from an initially equal weight mixture led to an effective separation of the proteins.