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Old-style cheese starters were evaluated to determine their ability to produce cheese aroma compounds. Detailed analyses of the aroma-producing potential of 13 old-style starter cultures were undertaken. The proteolytic profile of the starters was established by an accelerated ripening study using a model cheese slurry and compared with those of a commercial aromatic starter and commercial Cheddar cheeses. To evaluate the aromatic potential of the starter cultures, quantification of free amino acids liberated and volatile compounds after 15 d of ripening at 30 degrees C as well as sensory analysis were carried out. Results showed that proteolysis patterns of all 13 starter cultures in the curd model were comparable to those of commercial Cheddar cheeses. All tested cultures demonstrated the ability to produce high amounts of amino acids recognized as precursors of aroma compounds. Several differences were observed between the starters and commercial Cheddar cheeses regarding some amino acids such as glutamate, leucine, phenylalanine, proline, and ornithine, reflecting the various enzymatic systems present in the starters. Starters Bt (control) and ULAAC-E exhibited various significant differences regarding their free amino acid profiles, as confirmed by sensory analysis. In addition, identification of volatile compounds confirmed the presence of several key molecules related to aroma, such as 3-methylbutanal and diacetyl. Besides the aroma-producing aspect, 2 starters (ULAAC-A and ULAAC-H) seem to possess an important ability to generate large amounts of gamma-aminobutyric acid, which contributed up to 15% of the total amino acids present in the model curd after 15 d ripening. gamma-Aminobutyric acid is an amine well-known for its antihypertensive and calming effects., (Copyright (c) 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Cheddar cheese in curd form is very popular in eastern Canada. It is retailed immediately after cheese manufacturing and can be maintained at room temperature for 24 h to provide better texture and mouthfeel. Subsequently, the cheese curds must be stored at 4 degrees C. The shelf life is generally 3 d. In this study, Cheddar cheese curds were produced by adding a high diacetyl flavor-producing strain (Lactococcus diacetylactis) to a thermophilic-based starter. The objective was to achieve both postacidification stability to increase the shelf life and enhanced flavor. The addition of L. diacetylactis increased processing time but did not affect cheese composition or the evolution of proteolysis and texture. During cheese manufacturing, streptococci became the dominant microflora in all cheeses, whereas populations of Lactococcus cremoris and L. diacetylactis decreased. During cheese storage, viable counts of L. diacetylactis and Streptococcus thermophilus increased but the counts of L. cremoris decreased. During cheese manufacturing and storage, the concentrations of lactic acid and diacetyl increased rapidly in cheeses produced with L. diacetylactis. Citric acid and galactose contents remained high in cheese made without L. diacetylactis. Sensory evaluation indicated that cheeses containing the L. diacetylactis strain were more flavorful and also had less sourness and could be stored at 4 degrees C for up to 7 d.

This review explores recent advances in the use of immobilized cells for the production of metabolites used in the food industry, such as enzymes, amino acids, organic acids, alcohols, aroma compounds, polysaccharides, and pigments. Some food bioconversions such as fermentation of soy sauce and various hydrolysis are also considered. Special emphasis was placed on existing or potential industrial processes. This article also reports the effects of the reactor (configuration and working conditions), the immobilized cell physiological status (growing, nongrowing, or permeabilized), and of the carrier type, configuration, and size on the performance of immobilized cell systems. Compared with free cell fermentation, the main advantage of using immobilized cells is an increase in productivity, particularly in the case of continuous fermentation. For monoenzymatic reactions, nongrowing immobilized cells are often reported to exhibit a higher stability than free or immobilized enzymes.

The development of a method for the continuous mass production of liposomes is vital for the industrial use of liposomes in food products. The method should be mild enough to prevent denaturation of the encapsulated material, and the materials used for the preparation of the liposomes should be safe and edible. Among the methods available, microfluidization seems to be the most promising. Microfluidization consists of processing emulsions under high pressure through an apparatus called a Microfluidizer. This apparatus also allows the production of another type of lipid vesicle: milkfat-coated microcapsules composed of milkfat and emulsifiers. The main advantages of microfluidization include the continuous production of large quantities of lipid vesicles without dissolving the phospholipids in organic solvents. These vesicles could be used in various food products for a variety of objectives. The addition of encapsulated material in liposomes or in milkfat-coated microcapsules to cheese milk resulted in a retention of 80-90% of the vesicles in the cheese, compared to only 2-4% if the material was added directly to the milk in the unencapsulated form. Liposomes and milkfat-coated microcapsules could be used as enzyme carriers to accelerate cheese ripening, or as carriers for flavouring systems to improve the organoleptic properties of low-fat cheeses or to impart distinctive flavours to new speciality cheeses. These microcapsules could also be used in food products to avoid undesirable side-reactions during food processing, or to supplement food products with nutritious additives.