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Abstract
The source, type and amount of each ingredient in an ice-cream formulation and the manufacturing process affect the structure, stability and sensory perception of ice-cream. A range of new dairy ingredients is being used as alternatives to the traditional milk ingredients in the manufacture of ice-cream. The role of ingredients commonly used in ice-cream formulations and the effects of the manufacturing process on ice-cream properties are reviewed.
Dairy ingredients in ice-cream
Introduction
Ice-cream contains 35-42% total solids (TS), which comprises 10-16% milkfat, 9-12% milk solids non-fat (MSNF), 14-20% sugars, 0-0.4% stabilisers and 0-0.25% emulsifiers. The final ice-cream is a complex structured mixture comprising ~25% ice, ~50% air, 5% fat and ~20%) unfrozen serum. The source, type and the amount of each ingredient, as well as the processing conditions, affect the ice-cream's properties (Keeney 1974; Berger 1990; Goff 1997a; Marshall and Arbuckle 1996; Campbell and Pelan 1997). This paper reviews the effects of ingredient formulation and processing on ice-cream properties. Special attention is given to the role of dairy ingredients in ice-cream.
Manufacture of ice-cream
The processing of ice-cream involves the mixing of ingredients, homogenisation of the mixture, pasteurisation and ageing at 4[degrees]C before freezing in a scraped surface heat exchanger and hardening (Berger 1990). All processes involved contribute to the transformation of the ingredients in the mix into the final structured ice-cream product. The structural elements of ice-cream are ice crystals, air cells and fat aggregates, and they have a major influence on the sensory and the textural properties of ice-cream (Gelin et al. 1996; Goff 1997b). The proteins, through their influence on the stabilisation of the structural elements of ice-cream, also affect the ice-cream texture.
Homogenisation
Homogenisation of the ice-cream mix ruptures the original fat globules in milk and results in the formation of smaller globules with new exposed surfaces; these are stabilised by the proteins and the low-molecular-weight emulsifiers. The fundamentals of homogenisation and its applicability in ice-cream have been previously discussed (White 1981).
Pasteurisation
Various heat treatments (e.g. 71[degrees]C for 30 min, 82[degrees]C for 35 s or UHT) may be used to destroy undesirable micro-organisms. These heat treatments cause the destruction of pathogens in the ice-cream mix, improve the solubility of ingredients and melt the fat. The application of...