THERMAL STABILITY OF SOME COMMERCIAL NATURAL AND SYNTHETIC ANTIOXIDANTS AND THEIR MIXTURES

The thermal stability of some commercially available antioxidants alone or in binary or ternary mixtures was investigated in order to find the optimal combination of antioxidants for food processing. The synthetic antioxidants used were butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG) and tertiary-butyhydroquinone (TBHQ). Other antioxidants such as ascorbyl palmitate (AP), mixed tocopherols (TOCO) and monoacylglycerol citrate (MGC) were also employed. The effectiveness of these antioxidants and their combinations was assessed using the Rancimat test by measuring the induction period for the oxidation of sunflower oil after heating at 180C for 1 h and comparing it to the oxidation kinetics of the oil without added antioxidants. All antioxidants and their binary or ternary mixtures showed different degrees of thermal instability. TBHQ individually, among all the examined antioxidants, showed the highest thermal stability. On the other hand, AP as an antioxidant in sunflower oil exhibited low stability during heating. The thermal stability of AP could be enhanced by the addtion of BHA or BHT in binary mixtures at a ratio of 1:3 (w/w). In addition, the ternary mixture of AP, TOCO and MGC (65:25:10) in sunflower oil also showed a higher stability to thermal inactivation. However, the ternary mixture containing 0.13% AP, 0.05% TBHQ and 0.02% MGC provided the optimal protection during thermal treatment. Although a combination of 0.13% BHT, 0.05% AP and 0.02% MG was very effective synergistically at room temperature, it showed a higher susceptibility to thermal inactivation. It was     

A MACHINE FOR MEASURING YIELD POINT IN RAW MEAT

A simple machine is described for measuring yield point in strips of raw muscle, by registering maximum tension generated at a low rate of extension. Values are not highly dependent on the rate or degree of extension. The method has been used to measure rate of ageing at 15°C and 2°C, with parallel measurements of shear force in the cooked muscle. The machine provides a sensitive tool, complementary to the tenderometer, and particularly suited to studies on ageing.     

THERMAL TRANSPORT IN A MULTIPLE JET IMPINGEMENT OVEN

Three‐dimensional numerical simulation of flow field and heat transfer in a jet impingement oven with multiple jets was carried out. Distribution of local heat transfer coefficient on a model cookie in the oven cavity was obtained from the predicted flow and temperature fields, and compared with the experimentally measured values. Effects of air temperature (400, 450K) and air velocity (2.5, 5, 10 m/s), on the surface heat transfer coefficient were studied. Numerical predictions showed good agreement with the experimental results. It was found that heat transfer coefficient was a strong function of air velocity while air temperature had no effect on the heat transfer coefficient. Local heat transfer coefficient values ranged between 11 and 66 W/m²K whereas average heat transfer coefficient values ranged between 24 and 42 W/m²K. Results also showed that because of the presence of the suction fan in the oven, flow field near the model cookie surface was quite different from that for a jet impinging on a flat surface.     

APPLICATION OF A COMMERCIAL ENZYME PREPARATION IN THE BARLEY MALTING PROCESS

This paper presents data on barley micromalting with addition of the CELLUCLAST enzyme complex. This is a commercial, multicarbohydrase with distinct β-glucanase and proteinase activities. The enzyme was added to steeping and germination phases, in different quantities (0.05%; 0.75% and 0.1% of initial barley). The enzyme was added to different malting phases: to the 2nd and 3rd steep water, at the beginning of germination on the 1st day by spraying, on the 2nd day of germination and in combination of addition to 3rd steeping water and in germination start (50% of total quantity of each). CELLUCLAST enzyme had a significant effect on reduction of wort viscosity, extract difference, wort filterability and protein breakdown, depending on the quantity of added enzyme and the malting phase to which it was added. There was no negative effect on other malt quality parameters. The best values of cytolytic breakdown parameters (viscosity, extract difference, filtration rate) were obtained with addition of 0.075% of CELLUCLAST, on the first day of germination.     

VC406B纺丝机的改造

介绍了国产VC406B纺丝机的技术改造,通过有效的设备改造(变频系统、空调系统等)和合理的工艺改进,使本设备能够生产锦纶、涤纶和丙纶长丝。     

THERMOSTABLE AND THERIVIOLABILEISOFORMS IN COMMERCIAL ORANGE PEEL PECTINESTERASE1

Thermostable and thermolabile pectinesterase isoforms in commercial Valencia orange peel pectinesterase (Sigma Chemical Co., St. Louis, MO) were separated by affinity chromatography on a Heparin‐Sepharose CL‐6B column. Among the seven putative PE isoforms separated, three (P1, P2 and P3 with 70 kDa, 60 kDa and 27 kDa, respectively)‐were thermostable and four [P4, P5, P6 (35 kDa) and P7 (35 kDa)]‐were thermolabile, according to the qualitative and quantitative studies of thermal stability. The commercial PE showed 83.4% and 98.3% inactivation after heat treatment at 70C for 5 min and at 90C for 1 min, respectively. P2 was the most heat stable, with 85.5% inactivation at 70C for 5 min and 93.0% inactivation at 90C for 1 min. The thermolabile P6 and P7 could be inactivated at 70C for 5 min or at 90C for 1 min. Thermostable PE activity was 16.6% of total activity of the commercial PE based on heat treatment at 70C for 5 min, but only 1.5% based on heating at 90C for 1 min. The 90C for 1 min heat treatment might be better than the 70C for 5 min heat treatment to distinguish thermostable PE and thermolabile PE isoforms in Valencia oranges.     

A METHOD FOR MEASURING THERMAL TIME DISTRIBUTIONS IN CONTINUOUS FLOW HEAT EXCHANGERS

This study deals with the distribution of heat treatment of liquids which flow through heat exchangers. the distribution is induced by the combined effect of velocity and temperature gradients and is referred to as the thermal time distribution (TTD).
A tracer technique based on the acid hydrolysis of dextran was developed for assessing the TTD. the change in the shape of the molecular weight distribution (MWD) of the polymer during the course of the reaction was found to be related to the TTD exposure of the fluid and the shape of the MWD could be described by means of statistical moments.
A computer-based model for simulating the TTD in a tube heat exchanger, in turbulent flow, was developed together with a model for simulating the effect of the TTD on the change in the MWD during dextran hydrolysis. the simulation model gave results that were in qualitative agreement with the experiments.     

SDS900A型加弹机皮带调校原理与方法

简述了皮带调校的基本原理,以SDS900A型加弹机为例,介绍了主机速皮带、龙带、吸丝皮带偏斜的调校方法,为及时纠正偏斜皮带提供了理论依据和重要参考。     

A SURVEY OF THE PREVALENCE OF SALMONELLA AND OTHER ENTERIC PATHOGENS IN A COMMERCIAL POULTRY FEED MILL

A study of the prevalences of Salmonella, Listeria and thermophilic campylobacters in a dedicated commercial poultry feed mill was undertaken. Salmonella was frequently recovered in samples taken in the preheat and postheat treatment areas of the mill with the overall percentage of samples positive found to be 18.8% and 22.6%, respectively. Feed ingredients and dust collected in the preheat treatment locations within the mill were frequently contaminated with Salmonella (11.8% and 33.3% of samples, respectively). High prevalences of Salmonella were also detected in dust samples (24.2%) obtained from the postheat treatment area of the mill and from feed delivery vehicles (57.1%).
Listeria was also recovered from samples at pre- and postheat treatment areas within the mill with overall isolation rates of 14.1% and 18.5% observed, respectively. The most frequently observed species of Listeria recovered from samples in both areas within the mill was L. innocua, L. monocytogenes, L. grayi and L. welshimeri.
No thermophilic campylobacters were recovered from any of the samples analyzed in the current study.     

模糊控制技术在滚筒洗衣机上的应用

介绍了模糊控制全自动滚筒洗衣机的模糊控制技术:通过传感器检测被洗衣物的布量、洗涤液的浑浊度和温度,利用模糊推理的方法自动确定水位高低、水流强度、洗涤时间、漂洗次数和脱水时间.模糊控制技术的应用实现了衣物洗涤过程的全自动化,具有一定的智能功能     

自动机AMCAD中可编程对话框设计

分析了可编程对话框的结构，以自动机ＡＭＣＡＤ中的槽轮为对象，编制出ＡＤＳ对话框驱动程序．采用图文混排、幻灯片显示、图形的动态变换等技巧所编制的对话框程序比一般编程具有更强的错误检查和预见功能．     

VARIABILITY IN PHYSICOCHEMICAL PROPERTIES OF DRIED WHEYS FROM COMMERCIAL SOURCES

Variability in physicochemical characteristics of dried wheys was determined for samples collected from six commercial sources. Eight dried whey samples were collected from each plant over a six month period. The pH in water, percent ash, alkalinity of ash, solubility in water and in acid, and Browning Indexes with and without pronase digestion were determined for each dried whey. Whey proteins were evaluated by gel electrophoresis. Variability of pH in water and of percent ash were low for dried wheys from individual plants, however considerable variability existed in the other characteristics, both between plants and between samples from individual plants. Gel electrophoresis may be useful in evaluating the effects of whey processing and drying on whey proteins.