Dairy products and milk-based food ingredients - Natural Food Additives, Ingredients and Flavourings - page 421

the ratio 2:1. Guar gum has eight times the water thickening capacity of corn
starch and is used synergistically with carrageenans in fl avoured milk drinks to
provide texture and mouthfeel. The two additives also serve an important function
as stablisers, preventing destabilisation of product components and separation
during shelf-life. An alternative to guar gum is provided by xanthan gum (E415),
which is a polysaccharide food additive derived from the fermentation of glucose
by the bacterium Xanthomonas campestris to form a sugar-based polymer.
Xanthan gum can be used at very low addition levels and is thixotropic (Kamozawa
and Talbot 2010), which means that products which are shaken and thin during
distribution will thicken when stored at the point of sale.

17.3.3 Butter and dairy spreads
The collective term 'yellow fat spreads' applies to a range of fat-based spreads
made from milkfat and/or vegetable fat. It includes butter, margarines and low-fat
spreads. A 'fat spread' is a product properly described as a water-in-oil emulsion.
The fat forms the continuous phase, with water droplets dispersed as the
discontinuous phase. A 'low fat spread' in contrast is an oil-in-water emulsion:
water forms the continuous phase with stabilised oil droplets dispersed throughout.

Butter
The principal ingredient in butter is cream, which is derived from whole milk.
Butter may be either sweet cream butter, unsalted or salted, or lactic butter. In the
production of sweet cream butter the cream used should have a minimum pH of
6.6 and a titratable acidity of 0.10-0.20%. The seasonal variation in the fatty acid
profi le of milkfat will cause fat hardness to vary. It is usually harder in the winter
than the summer. If the iodine value of milkfat is low, indicating a high level of
saturated fat, then hard butter will be produced. Conversely, a high iodine value,
indicating a higher proportion of unsaturated fat, will give a butter with a greasy
mouthfeel. Iodine values between 28 and 42 give butter of a satisfactory quality.
Modern processes for sweet cream butter manufacture are based on continuous
processing technologies, having moved away from traditional batch manufacture
in a butter churn. Continuous processing is based on the Fritz method, which itself
is based on traditional churning methods. The Fritz process has four stages:

￿ ￿ ￿ ￿ ￿

1 Separation of cream to a fat content of 40-42%
2 Crystallisation of the fat in the cream
3 Phase inversion of the cream to further concentrate the milkfat
4 Working of the butter to achieve an even moisture droplet distribution.

Cream is produced by separating the milkfat globule fraction of whole milk by
means of centrifugal separation using a cream separator. The by-product is
skimmed milk. Following separation cream is heat treated at 85-95°C for 10-30
seconds, which destroys pathogenic and spoilage bacteria. It is then passed
through a vacuum de-aerator where volatile sulphides and other compounds are
removed and cooling occurs. In the crystallisation stage, cream is cooled to 8°C