国内外拉伸型干酪的种类及研究进展

概述了拉伸型干酪的种类、工艺,以及国外拉伸型干酪的研究进展.同时研讨了我国少数民族传统拉伸型干酪-乳扇的生产历史、工艺、研究情况,以及与国外传统拉伸型干酪的比较;并介绍了国内对Mozzarella干酪的研究进展.     

Development and evaluation of active packaging for sliced mozzarella preservation

Antimicrobial films were formed by the incorporation of nisin (NI), natamycin (NA) and a combination of both (NI + NA) into cellulose polymer. Film efficacies were evaluated in vitro against Staphylococcus aureus ATCC 6538, Listeria monocytogenes ATCC 15313, Penicillium sp. and Geotrichum sp. The films were also evaluated on sliced mozzarella cheese against moulds and yeasts, Staphylococcus sp. and psychrotrophic bacteria. Mechanical and microscopic properties of the films and the diffusion of the antimicrobial agents from the film to the cheese were also evaluated. Films containing NI showed an antimicrobial effect in vitro against S. aureus and L. monocytogenes, while films containing NA were effective in vitro against Penicillium sp. and Geotrichum sp. By the ninth day of storage at 12 ± 2°C, the count of yeasts and moulds on cheese covered with films containing NA decreased 2 log10 units compared with the count on cheese with control films. NI film did not show an effect against Staphylococcus sp., but it was effective against psychrotrophic bacteria for 6 days of storage of the cheese. The incorporation of antimicrobial compounds decreased the resistance and elongation of the films and caused changes in their molecular conformation. NI diffusion from the films to the cheese was not detected; however, time‐dependent diffusion of NA from the film containing NI + NA was measured. The incorporation of NI and NA together in the films did not show an effect. The film containing NA showed potential for application as active food packaging for sliced mozzarella cheese. Copyright © 2008 John Wiley & Sons, Ltd.     

Conjugated Linoleic Acid Concentrations in Dairy Products as Affected by Processing and Storage

Total conjugated linoleic acid (CLA) concentrations increased 1.32 fold in salted and 1.27 in unsalted butter but did not alter the ratio of 9-cis 11-trans to total CLA. Nonfat yogurt showed an increase in CLA content with processing (5.25 mg total CLA/g fat) compared to unprocessed raw material (4.40 mg CLA/g fat). No changes in CLA content was observed in processed dairy products such as lowfat yogurt, regular yogurt, lowfat and regular ice cream, sour cream or cheeses such as Mozzarella, Gouda and Cheddar. Storage did not affect CLA concentration in any products suggesting that CLA is a stable component.     

Test for measuring the stretchability of melted cheese

A test for measuring the stretchability of cheese was developed by adapting a texture-profile analyzer to pull strands of cheese upwards from a reservoir of melted cheese. Seven different cheeses were analyzed using the Utah State University stretch test. The cheeses were also analyzed for apparent viscosity with a helical viscometer, for meltability using a tube melt test, and for stretch using the pizza-fork test. Cheese was placed into a stainless steel cup and tempered in a water bath at 60, 70, 80, or 90 degrees C for 30 min before analysis. The cup was then placed in a water-jacketed holder mounted on the base of the instrument. A three-pronged hook-shaped probe was lowered into the melted cheese and then pulled vertically until all cheese strands broke or 30 cm was reached. This produced a stretch profile as the probe was lifted through the reservoir of melted cheese and then pulled strands of cheese upwards. Three parameters were defined to characterize the stretchability of the cheese. The maximum load, obtained as the probe was lifted through the cheese, was defined as melt strength (F(M)). The distance to which cheese strands were lifted was defined as stretch length (SL). The load exerted on the probe as the strands of cheese were being stretched was defined as stretch quality (SQ). There was a correlation between F(M) and apparent viscosity. There was also some correlation between SL measured by the fork test and SL when the cheese was tested at 90 degrees C, but no correlation occurred at lower temperatures.     

Effect of Curd Washing Level on Proteolysis and Functionality of Low-Moisture Mozzarella Cheese Made with Galactose-Fermenting Culture

Abstract: The effect of curd washing on functional properties of low-moisture mozzarella cheese made with galactose-fermenting culture was investigated. A total of 4 curd washing levels (0%, 10%, 25%, 50% wt/wt) were used during low-moisture mozzarella cheese manufacture, and cheeses were stored for 63 d at 4 °C and the influence of curd washing on proteolysis and functionality of low-moisture mozzarella cheese were examined. Curd washing had a significant effect on moisture and ash contents. In general, moisture contents increased and ash contents decreased with increased curd washing levels. Low-moisture mozzarella cheese made with 10% curd washing levels showed higher proteolysis, meltability, and stretchability during storage than other experimental cheeses. In general, galactose contents decreased during storage; however, cheeses made with 25% and 50% curd washing levels had lower galactose contents than those with control or 10%. L*-values (browning) decreased and proteolysis increased in low-moisture mozzarella cheeses during storage.     

莫扎雷拉干酪的工艺介绍

探讨制作莫扎雷拉干酪的制作工艺及拉伸工艺中的影响因素。经过试验,发现要获得优良的拉延特性,干酪凝块的最佳pH应控制在5.2~5.4,产品的钙/非脂乳固体比例约为3.1%±0.1%,水分含量为55%±2%,无脂干酪的水分含量为70%±3%,残糖含量按半乳糖计为7 g/kg,无乳糖残留。     

Analysis of the water-soluble compounds as a tool for discriminating traditional and industrial high moisture mozzarella made with citric acid

High moisture mozzarella from cow milk is a pasta filata cheese that can be manufactured by different protocols. Fermentation by autochthonous starter is used for the traditional product, whereas direct acidification with citric acid is widely used at industrial level. Both types are stored immersed in a liquid for preserving freshness, but this packaging method is known to favour the changes of the quality characteristics. The present study aimed to assess the evolution of the soluble compounds and to evaluate their use as chemical indices for discriminating the two types of mozzarella. The contents of lactose, organic acids, water-soluble nitrogen and free amino acids differently changed over time. The whole patterns of these soluble compounds allowed discrimination of the two products during the whole storage period. The simple analyses of lactic acid and lactose could be a rapid tool to protect traditional mozzarella from industrial imitations obtained with citric acid.     

The effect of homogenization and milk fat fractions on the functionality of Mozzarella cheese

Mozzarella cheese was manufactured from milk containing either a low (olein) or a high (stearin) melting point fraction of milk fat or anhydrous milk fat. The fat was dispersed into skim milk by homogenization at 2.6 MPa before being manufactured into cheese. The melting point of the milk fat did not affect the size or shape of the fat globules, nor was there any effect of homogenization on the polymorphic state of the milk fat. There were no changes in milk fat globule size and shape concomitant with the amount of free oil formed. The polymorphic state of the milk fat did affect the amount of free oil formed and the apparent viscosity of the cheese. The lower melting point fraction yielded a larger amount of free oil. The higher melting point fraction yielded a higher viscosity of melted cheese at 60 degrees C. Mozzarella cheese was also manufactured from homogenized milk, nonhomogenized milk, and a 1:1 ratio of the two, without altering the milk fat composition. Increasing the proportion of homogenized milk yielded a lower free oil content and higher viscosity of the cheese.     

Volatile organic compounds in milk and mozzarella: Comparison between two different farming systems

The volatile organic compounds (VOC) and sensory characteristics of milk and mozzarella from farms with different rearing systems were compared. Milk samples were taken from 9 intensive (INT) and 13 semi-extensive farms (EXT) in the grazing period. VOC were analysed by SPME-GC-MS, and sensory evaluation was carried out by paired comparison. The volatile profiles of milks were significantly different: acetone and isopropyl alcohol characterised INT milk, pentanoic and decanoic acids, hexanal, ethylacetate, toluene, dimethyl sulphide characterised milk from EXT farms. Also mozzarella was discriminated by VOC, but only a few compounds derived from milk. Based on sensory evaluation, milk from the two sources can be distinguished by odour and colour, mozzarella only by colour. It was hypothesised that heating during the stretching phase caused volatilisation of many milk volatile compounds and formation new aroma active molecules that overcame the ‘primary odours’ of milk.