Freeze quality preservation

The latter plays an important role with freeze-dried sour dough. The microorganisms cultivated on flour substrate already form a number of flavour constituents, which stick well to the flour matrix. The subsequent freeze drying preserves both, flavour and microorganisms. The resulting product saves time in the bakery and improves the quality of bread. 

Cooling and freezing cannot improve a product, and the hest that can he achieved is to keep it near to the condition in which it entered the cooling process. This means that only the hest produce should he used, and this should he as fresh as possible. (This general principle must, of course, be interpreted in the light of local conditions and needs. In some countries of the world, preservation in cold stores is essential to prevent wastage, regardless of the quality of the crop.)... 

Looking back also over the historical development of quality requirements for processed foods, freezing when properly carried out is undoubtedly the most satisfactory method for the longterm preservation of vegetable produce. The low temperatures commonly prescribed for frozen foods (—18°C) can maintain initial quality and nutritional value practically unchanged, so that frozen and fresh vegetable products differ only in texture (Canet, 1989), which is however a particularly important quality attribute in potato products. 

Although freezing will disrupt the cell structure of soft fruit and render it pulpy upon thawing out, any adverse changes to juice quality will be minimal and flavour and colour can be easily preserved by this treatment... 

The storage of freeze-dried carrots for 24 months in sealed cans under air and N2 and in glass containers under vacuum at room temperature was studied by Gegow [4.29]. Fifteen quality parameters were evaluated and found to be comparable to those of frozen carrots. The carotenes were only reasonably preserved under vacuum. 

The texture of traditional and novel formulated foods, its formation, modification, and/or preservation during processing (frying, cooking, freezing, etc.) and storage is one of the key quality aspects. Food texture, therefore, is important for the success of a food both in the marketplace and for consumption. 

Maelkki Nikkilae, Aalto and Heinonen [31, 32] stress the importance of the raw material quality of onions. Stieger [33] has investigated the suitablity of various strawberry varieties. Processes for flavour preservation have been thoroughly examined with cultivated mushrooms, leading to an illumination of the most important freeze drying parameters [34[. 

A way to preserve vegetables vs. time is first to blanch them and afterwards to cool them in order to transform available liquid water into ice. This process is called "freezing" and has been established as an excellent method for preserving high quality in foods (Reid, 1983). Nucleation (formation of ice crystals) and crystal growth are the two major thermal events of the... 

Since initial flavor is preserved, the most important consideration for freeze concentration is that feed juices be of very high quality. For example, juice from immature or overmature, or a few rotten fruit, may contain off-flavors which will still be present in the finished product. Also, juice handling practices prior to actual concentration will affect final product quality. 

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