For SMP, cooked flavours may be present and vary according to heat treatment (low, medium, high) of the milk prior to evaporation and spray drying ( Drake et al., 2003).Ī. (2003) undertook descriptive profiling of milk powders and observed that milk fat, fried, fatty/painty flavours were not detected in SMP, but were observed in WMP. These off-flavours may be described as being ‘tallowy’, ‘rancid’, ‘oxidised’ or ‘glue-like’. WMP are particularly more susceptible to oxidation due to their higher fat contents, especially at elevated temperatures (>30☌) ( Pearce, 2016). This is generally applied before bagging which may involve some form of gas flushing (N 2, CO 2 or both) to prevent oxidation during storage. Lecithinisation is sometimes used for WMP, because of the higher fat content, which involves covering the powder particles with a thin layer of lecithin to confer better reconstitution properties. The powder produced should be free flowing and not stick to containers, vessels, bags etc., and should reconstitute in water readily, without lumps or undissolved particles ( Walstra et al., 2006e Pearce, 2016). A fluidised bed process may also be employed at this stage which involves air being blown up through the powder from below, causing the powder particles to separate and behave like a fluid, as well as to cool and dry the powder further. The bacterial load is dramatically reduced and the low moisture content of the resulting powder inhibits microbial growth producing a long shelf life product (∼1 year). After spray drying, the milk powder is separated from the air in the dryer by a bag filter or cyclone. For whole milk powder (WMP) a portion of the cream is added back to the skim milk to produce a milk with a standardised fat content with typically 26–30% fat in the powder ( Pearce, 2016). Pasteurised milk is firstly separated into skim milk and cream before concentration through evaporation to 45–52% solids. Milk powders are produced, without extensive loss in quality, by drying milk in spray driers ( Fig. 12.1) which atomise the milk in a stream of heated air which rapidly dries the milk into a powder in a matter of seconds. Skim milk powder (SMP) and other dried dairy ingredients should ideally have a clean, sweet and pleasant taste free of flavour defects ( Bodyfelt et al., 1988).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |