As stated in other science posts, ice cream has 7 categories; fat, milk-solid-non-fat(msnf), sweetener, stabiliser, emulsifier, water and flavour. Msnf, also known as protein, is one of the fundamental ingredients. In this post, we will talk about types of protein and the functional role of protein in ice cream production.
1. Types of protein
Raw materials such as milk, cream, condensed milk, skim milk powder are typical options that supply protein in ice cream production. Other protein sources can be whey protein powder that is a substitute of traditional msnf but since they are synthetically blended, so some flaws such as off-flavour may be brought up in light-flavoured ice cream like Vanilla. Protein in structure is comprised of 80% casein and 20% whey protein.
2. Role of protein in ice cream
2A. Emulsification
Ice cream mix is an emulsion that fat is in the water and since emulsion is chemically unstable, meaning that there is a tension between the fat oil and water to separate them, and thus both parties need this emulsifying function from protein to stabilise it before churning in ice cream machine. Protein from msnf are absorbed to the suface of the fat globules to form a membrane or layer after pasteuriation and homogenisation, and this thick membrane is responsible for stabilising the emulsion in which all the concentrates of sweeteners, fat globules, msnf, vitamins and so on are bonded together.
2B. Promotion of Fat destablisation (Partial Coalescence) & Aeration
Partial coalescence is the process that some parts of the fat globules of the aged ice cream mix coalesce when being agitated in the ice cream machine, through which it enables the air bubble from the shear force gets trapped in these coalesced fat and spread becoming smaller in size, and thus to build up ice cream structure and smooth texture. Since the stabilised emulsion with protein layer absorbed is more prone to have a proper partial coalescence, protein is then a necessity.
2C. Stabilising property
Air is normally not counted in the categories because it is invisible but it plays the key role in stabilising the structure during aeration (air bubble trapped in between the ice cream). As new air bubble is not stabilised enough, the thick protein layers and the partially coalesced fat globules will help stabilise the air bubble in order to promote a creamy mouthfeel and prolong the melting time.
Summary
Protein's lecithin has a function to emulsify emulsion. In ice cream production, protein enables the serum to promote partial coalescence more easily, which is a phenomenon, sort of standard to promote a smooth, firm product when being withdrawn from the machine. With a proper partial coalescence, tiny ice crystals and air bubbles are dispersed in between the fat globules to build up a sturdy ice cream structure that will prolong the melting time as well as the shelf life during static storage in the freezer.
Reference
Goff & Hartel Ice Cream 7th Edition
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