ISSN:1364-727X    

DOI:10.1111/j.1471-0307.1994.tb01264.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The LacTek Beta‐Lactam Milk Screening Kit (an enzyme immunoassay) was compared to the Delvotest P method (a microbial inhibition test) for detecting antibiotics in raw milk samples. Good agreement (97·8%) was obtained from a total of 413 raw milk samples tested in four laboratories, The LacTek test has been accepted as a rapid (less than 10 minutes) antibiotic screening method for inclusion in the Joint Committee of the Milk Marketing Board and the Dairy Trade Federation Code of Practice for the Assessment of Milk Quali

ISSN:1364-727X    

DOI:10.1111/j.1471-0307.1994.tb01265.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The methods used to manufacture butter (the Fritz process and batch‐wise churning) basically transform cream into butter grains and buttermilk by agitation and by beating air into the cream. Electron micrographs have been used to show the individual stages of buttergrain formation (ie, phase reversal from oil‐in‐water into water‐in‐oil):(1) building up foam from the skim milk, (2) adsorption of fat globules at the foam lamellae and (3) agglomeration of fat globules, (4) destabilization of the foam and mechanical clumping of the agglomerates to form butter grains. The microstructure of the butter grains as well as of the finished butter is characterized by a dispersion of water, air, fat crystals and fat globules in oil. By contrast, margarine has a more homogeneous structure. It does not contain globular fat. Thus the texture of butter tends to be solid, while that of margarine tends to be greasy. The consistency of butter can be influenced to a large extent by temperature treatment of the cream (physical cream ripening). A simple device has been developed for optimizing physical cream ripening which automatically records the melting and crystallization curves of the fat. Many raw material, process and machine specific parameters affect the efficiency of churing as well as the quality of butter, and many of these parameters exert an opposite effect. They therefore have to be set carefully so that they balance each other as required. Dosage of buttermilk and dried skim milk into the product stream has allowed the fat content of butter to be reduced to 60% and the water content to be increased to 36% without impairing product quality. This method has been developed further (Pasilac) for manufacturing a stable, long keeping half‐fat and quarter‐fat butter (the latter in only a few experiments so far). The structure of these products is not of the oil‐in‐water dispersion type. It could be characterized as a water‐in‐oil/fat dispersion, which contains an additional locally continuous aqueous phase. The Alfa buttermaking process (which was used during the 1950s and early 1960s) has recently been revived for the production of the Swedish mixed spread, Bregott, in order to minimize fat losses and to increase further maximum levels of oil inclusion in the blend. Blended spreads comprising milk fat (60­75%) + vegetable oil (25­40%) are no doubt more spreadable than butter at refrigerator temperature. However, they have proved to be too soft above 16­18°C. Therefore experiments have been undertaken to improve the consistency of blended spreads by using different milk fat fractions. In order to preserve the butter character artificial creams have been prepared and churned. The fat mixtures were emulsified in skim milk. Distilled unsaturated monoglycerides were added to the fat phase at different concentrations (0­2%) to make the emulsions sufficiently unstable at low temperatures. Beyond a certain monoglyceride concentration the emulsions could be churned successfully. However, below this critical concentration (which corresponds to roughly half of the mass required for covering all fat globules with monolayers) churning efficiency decreased significantly. Electron micrographs elucidate the mechanism of destabilizing the cream by monoglycerides. Electron micrographs also reveal the globular structure of the products thus obtained. Globular structures are known to cause the typical butter like mouth feel. The firmness/temperature curves of spreads obtained by churning adequately blended fat emulsions could be improved over those of butter (ie, flattened and shifted). In addition, the consistency, as in the case of ordinary butter, could equally be influenced

ISSN:1364-727X    

DOI:10.1111/j.1471-0307.1994.tb01266.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The operating efficiency of a laboratory scale microfluidizer had been compared to that of a high pressure valve homogenizer using either pasteurized whole milk or recombined milk. Microfluidization was found to be a very effective method for reducing fat globule size and was only slightly affected by changes in operating pressure. The back pressure module on the microfluidizer had a marginal effect on particle size increase. As a result, the homogenization effect was always greater than that of conventional homogenization. Only very small amounts of serum protein but high levels of casein were found on fat surfaces after microfluidization. The protein load was higher than predicted on the basis of decreases in globule size. Microfluidization had little effect on the formation of fat clusters in milk. The higher protein load probably inhibited fat clustering.

ISSN:1364-727X    

DOI:10.1111/j.1471-0307.1994.tb01267.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The use of intense sweeteners in the manufacture of low calorie frozen desserts has brought about the need to add bulking agents to replace the sugar omitted in such products. A bulking agent acts as a filler and reproduces the physical properties of sugar, but not its sweetness and caloric content. Careful attention must be paid to combining sweeteners (polyols) with bulking agents in order to regulate the freezing point of the mix, and to restrict the levels to those which do not impart off­flavours or create gastrointestinal distress. Some modifications in the freezing and serving conditions are needed with the addition of bulking agents. The newlmodified bulking agents need to be approved by the regulatory bodies to ensure their safety. There is a need to identify a low or non‐caloric bulking agent with little or no laxative effe

ISSN:1364-727X    

DOI:10.1111/j.1471-0307.1994.tb01268.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY