Other Dairy Products and Starter Cultures

In addition to ice cream, milk, yogurt, and cheese some other dairy products can be frozen, such as cream and butter. Cream can be frozen in bulk containers for shelf-life increment, but after thawing, fat and serum separation is an extremely big concern. If pasteurized and homogenized to restore emulsion, this kind of cream can be used as a component in cream soups, recombined milk, butter, or ice cream. Sugar addition or increasing nonfat solid content can prevent fat coalescence considerably, due to lowering the freezing point. Freezing rate is not the determinant factor on fat emulsion.

Although quality characteristics of butter are not sensitive to freezing conditions regarding having lower water content up to 20%, freezing after production of butter is more acceptable than freezing after chilling step. Butter is a water-in-oil emulsion, so its behavior during freezing is very different from that of most food products, for which water forms a continuous phase. Because the major concern is off-flavor gain during storage, frozen butter should be covered properly. Storage time, temperature, and package type affected butter flavor, oxidative stability index OSI, peroxide value PV, and free fatty acid value FFV (Krause et al., 2008).

Starter cultures in dairy products are traditionally in liquid form. After the 1960s, commercial requirements led to new solutions due to a need for proper transportation and shelf life. Newly developed technologies such as freeze-dried cultures are preferred nowadays, and they can directly inoculate into the cheese vats, eliminating the need for using buffers and bulk tanks. These cultures are called direct vat set (DVS) or direct-to- vat inoculation (DVI) cultures. DVS cultures can be packed in an inert gas, and their activity can be prolonged up to one year for frozen and two years for freeze-dried cultures.

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