巧克力牛奶乳化剂的复配及优选

以分子蒸馏单甘酯和不同HLB值的蔗糖酯为原料复配巧克力牛奶乳化剂，在比较其乳化效果差异的基础上，同时就各个乳化剂的成本进行比较，从而优选出乳化效果好、成本低廉、耗能较少的乳化剂投入实际应用。通过模拟试验证明，当分子蒸馏单甘酯和HLB值为15的蔗糖酯以1：1的比例复配时的效果最佳。     

THE EFFECT OF TEMPERATURE ON THE RHEOLOGY OF BUTTER, A SPREADABLE BLEND AND SPREADS

The texture of lipid-based food materials is an important topic for investigation. In this study, the rheological properties of five edible fats were determined. A puncture test was performed to investigate the rheological properties of the food materials at 5C and at 19C using a texture analyzer. The force-displacement measurements were converted to stress–strain by assuming incompressibility of edible fat food materials in a linear viscoelastic region (LVR). Young's modulus of each edible fat was calculated using stress–stain curves in a LVR. Shear elastic moduli of edible fats in a LVR were obtained using a rheometer. Further to that the effect of temperature on storage modulus and loss modulus and creep test were obtained using a rheometer. The tests showed good correlation between Young's modulus and shear elastic modulus for each material. The mechanical properties correlated well with the structural properties of each of the materials.

PRACTICAL APPLICATIONS

The texture of butter, blends and spreads is determined by temperature, rheological properties, processing conditions and the composition of the material. Our research investigated the effect of temperature on the rheological properties of these foods. The results may be used to model the relationship between the microstructure and mechanical properties of the fat crystal network.     

活性炭对聚丙烯腈共混熔液流变性的影响

共混是合成纤维改性常用的方法．用活性炭与丙烯脯─氯乙烯共聚体共混制得纺丝溶液,以二甲基甲酰胺为溶剂湿法纺丝制造了吸附和阻燃双功能聚丙烯膊纤维．本文主要探讨了共混溶液中活性炭含量,温度等条件对纺丝溶液流变性能的影响．     

WHEY PROTEIN DENATURATION OF UHT PROCESSED MILK AND ITS EFFECT ON RHEOLOGY OF YOGURT

The denaturation of whey proteins in whole milk during processing by the indirect UHT and vat systems was determined. Whey protein denaturation plateaued at about 88% following a UHT heat treatment of 149°C for 10 s. However, it reached about 88% with a vat heat treatment of 82°C for 5 min and reached 95 to nearly 100% after 10 to 15 min. Vat processing under pasteurizing conditions at 63°C for 30 min resulted in less than 10% denaturation. The yogurts prepared from the vat processed milk had considerably higher structural firmness than those prepared from the UHT milk, as confirmed by the lower value of curd firmness and the higher shear stress of these yogurts. It was also found that the structural or curd firmness of yogurts prepared from UHT milk was highest when the milk was processed for 3.3 s process holding time and was lower when the milk was processed for longer or shorter process holding times. The results suggest that the vat process at 63°C or 82°C brings about a specific change in the whey protein which leads to formation of a firm structure. This change apparently does not occur during the brief UHT treatment.     

食品流变学的研究进展

简要介绍了食品流变学的起源、发展、分类、数学模型，测量仪器和方法的研究进展情况。     

THE EFFECT OF EEC REGULATIONS ON THE MARKETING OF MILK AND MILK PRODUCTS IN THE UK

The effect on the dairy industry of membership of the EEC and the distinction between its regulations and directives as set out in the Treaty of Rome are described. Over 3,000 regulations were issued in 1974, 250 of which dealt with milk and dairy products and a list of the main regulations is given in an appendix. The advantages of price reviews more than once a year and possible seasonal milk pricing are discussed. The marketing field is described and the need for products with the greatest earning potential stressed. Developments in liquid milk markets are shown and their importance in the United Kingdom emphasized. Possible standardization in the liquid milk market, and the difficulties involved in the operation of milk marketing boards is considered. {Editor's summary).     

MEASUREMENT OF YIELD STRESS IN DARK CHOCOLATE USING CONTROLLED STRESS VANE METHOD

The controlled stress vane method was used to measure the yield stress in dark chocolate. Three vanes with different L/D ratios and five different stress rates were used in three different chocolate formulations. The vane displacement data did not indicate a definite yield phenomenon. When the vane displacement data were transformed into a ratio of vane velocity to elapsed time, the square root of vane velocity (SV) or the cube root of displacement, a definite yield phenomenon was observed. The SV was preferred on the basis of physical considerations and the linear regression of its derived yield stress on vane dimensions, stress rate and chocolate particle size. The value of the yield stress was the least when determined for a vane height to diameter ratio of 2 and at a stress rate of 3 Pa/min using the SV transformation.     

EFFECT OF PROTEIN CONTENT OF MILK ON THE STORAGE AND LOSS MODULI IN RENNETING MILK GELS

A series of skim milks was made up with protein levels in the range 3 to 5 g/100g using ultrafiltration. The rheometric behavior during renneting was measured using low-amplitude oscillatory shear. Gel times were determined in terms of storage modulus G′, loss modulus G″ and tan δ (=G”/G′), respectively and were modelled in terms of protein level and enzyme level. Coagulum cutting time was defined in terms of G′. A prediction equation was developed for coagulum firming time in terms of gel time and protein level. The consistency of ultimate tan δ, over the range of protein and milks, showed that G″ at coagulum cutting was related to G′ and hence an on-line system could monitor coagulum firming rate by sensing either G′ or G′, or any related parameter, such as viscosity or complex modulus.     

EFFECT OF COLD STORAGE ON CULTURE VIABILITY AND SOME RHEOLOGICAL PROPERTIES OF FERMENTED MILK PREPARED WITH YOGURT AND PROBIOTIC BACTERIA

ABSTRACT

We examined the effect of storage time on culture viability and some rheological properties (yield stress, storage modulus, loss modulus, linear viscoelastic region, structural recuperation and firmness) of fermented milk made with Lactobacillus delbrueckii ssp. bulgaricus, Lactobacillus acidophilus (LA) and Bifidobacterium animalis ssp. lactis in coculture with Streptococcus thermophilus (ST). Acidification profiles and factors that affect viability (postfermentation acidification, acidity and dissolved oxygen) were also studied during 35 days at 4C. Fermented milk prepared with a coculture of ST and Bifidobacterium lactis gave the most constant rheological behavior and the best cell viability during cold storage; it was superior to ST plus LA for probiotic fermented milk production.

PRACTICAL APPLICATIONS

Probiotic cultures should grow quickly in milk, provide adequate sensory and rheological properties to the product, and remain viable during storage. Commercially, it is very common to use yogurt starter culture (i.e. Streptococcus thermophilus[ST] and Lactobacillus delbrueckii ssp. bulgaricus) in combination with the probiotic bacteria in order to reduce fermentation time. However, LB tends to post acidify fermented milk, which reduces the viability of the probiotic bacteria; thus, it is recommended to use starter cultures devoid of this species. We found that the technological properties and the viability of the probiotic bacterium Bifidobacterium animalis ssp. lactis BL O4 in coculture with ST make it suitable for probiotic fermented milk production; it produces rheological characteristics similar to those of yogurt.     

水溶性高分子聚合物对喹吖啶酮颜料分散体系流变性质的研究

研究了不同类型水溶性高分子聚合物对喹吖啶酮颜料(颜料红122)分散体系流变性能的影响。实验结果表明：加入不同类型高分子聚合物后，颜料红122分散体系的粘度随剪切速率增大而下降，即剪切变稀，采用Herschel—Bulkley模型描述加入不同类型高分子聚合物后颜料红122分散体系的剪切速率—剪切应力变化曲线，并使用稠度系数、流动特性指数和屈服值表征了不同类型高分子聚合物对分散体系流变性能的影响。     

高温法二醋片丙酮溶液的流变性及可纺性探讨

本文用旋转粘度计法和干法纺丝研究了高温法二醋酸纤维素酯（简称二醋片）丙酮溶液在不同温度、浓度下的流变性，并考察了其可纺性。研究结果表明：高温法二醋片丙酮溶液为切力变稀流体，其粘弹性较低；过滤性和可纺性能良好，纺制烟用二醋纤维主要物理指标为纤度３．１～５．０ｄｔｅｘ，断裂强度０．７４～０．９７ｃＮ／ｄｔｅｘ，伸长率１８～２８×１０－２，基本符合嘴纤半制品要求。     

THE EFFECT OF MILK COMPOSITION, DENSITY AND TEMPERATURE ON QUANTITY MEASUREMENT

Calibrated measuring vessels change their capacity with temperature but the calculation of corrections is straightforward and easy to apply. Measurement by weighbridge is dependent on density but if the temperature and composition of the liquid are known, density can be deduced to within 0.05 per cent from the data given. The arbitrary use of different standard temperatures complicates the picture. Meters are available for any of the liquid dairy products and the best way to achieve accuracy is to calibrate with the right liquid at the right flowrate and the right temperature. Above all, with meters it is important for the installation to be right.     

Flow Characterization of Peach Products During Extrusion

Suitability of Bingham, Herschel-Bulkley, Casson, and Mizrahi-Berk models, to characterize the flow behavior of peach products during extrusion was investigated. The Casson equation sufficiently described the flow of peach extrudates within the 49 to 125 s^-1 shear rate range. As concentration increased, yield stress and consistency coefficients increased. A rheological model was proposed to describe the viscosity of peach extrudates. The model incorporates the effect of shear rate by the Casson equation and the effect of concentration by a linear expression. The model provided good fit to the experimental data for peach extrudates reconstituted from drum-dried peach purees.     

盐及非盐物质对低浓度魔芋胶溶液粘度影响的研究

研究了盐（阴、阳离子）及非盐乙醇、蔗糖及柠檬酸对低浓度（0.25%）魔芋胶溶液粘度的影响。结果表明,大多数阴、阳离子对其粘度影响不大,低浓度NaCl、KCl、Na2SO4和Na2HPO4使溶液粘度略有增高,低浓度FeCl3、AlCl3和Na2CO3使溶液粘度略微降低;乙醇能使溶液粘度增高;蔗糖和低浓度（小于7.50mg/L）柠檬酸能使溶液粘度略微增高。