Heat transfer treatments, protein

Often, foods must be treated as engineering materials. Heat has to be transported so that the components become cooked or harmful microorganisms and toxins become inactivated. Even in the kitchen, mixing involves the mass transfer of liquids and solids to form metastable structures, which are fixed by subsequent treatment by heat or cooling. Heat transfer properties are crucial in the formation of ice crystals in ice cream and fat crystals in chocolate products. Food materials have been used as a source of industrial components soybean proteins to manufacture auto parts in the 1940s, casein to make buttons and knitting pins, and starches in adhesives and thickeners. 

Preparation of dry beans involves preliminary hydration followed by various heat treatments to obtain a tender, palatable product. Water and heat play an important role in chemical reactions, heat transfer and chemical transformations, such as protein denaturation and starch gelatinization. Inadequate water uptake may result in insufficient heat transfer to inactivate antinutritional factors and result in reduced cookability. In general, beans with an initial moisture content between 12 and 18%, are soaked to hydrate the seed to a moisture content of 53 to 57% and subsequently blanched, cooked or canned. This cooking step, if done for an optimal time, renders the seed nontoxic, improves digestibility, develops acceptable flavor and softens the seed coat and cotyledon. 

Milk contains specific binding proteins for retinol (vitamin A), vitamin D, riboflavin (vitamin Bj), folate and cyanocobalamin (vitamin Bi2)- Such proteins may improve the absorption of these vitamins by protecting and transferring them to receptor proteins in the intestine, or they may have antibacterial activity by rendering vitamins required by intestinal bacteria unavailable. The activity of these proteins is reduced or destroyed by heat treatments. 

Yamada et al. (1978) demonstrated again this transfer in the following way. Microsomes labeled with were prepared by feeding [ Cjacetate to endosperm tissue slices from 4-day-old castor bean seedlings and incubated with unlabeled mitochondria from the same tissues. The loss of C lipids from microsomes was accompanied by an increase in lipids in mitochondria. The addition of a 105,000-g supernatant, and a further pH 5.1-treated supernatant prepared from castor bean endosperms at the same stage, markedly enhanced the lipid transfer from microsomes to mitochondria. The activity of the added fraction was precipitated by ammonium sulfate and lost after pepsin or heat treatment. Thus it was concluded that in castor bean endosperms phospholipids were transferred from the endoplasmic reticulum to mitochondria and that this exchange was mediated by a protein contained in the cytosol. In castor bean tissues, the transfer of lipids was limited to phospholipids (Table III). 

The major advantage of enzymatic processes is the possibility of using conventional technology already existing in textile plants. Enzyme formulations should be applied in solution, to avoid dust formation and to reduce the known allergizing potential of protein material when inhaled. A heat treatment is sufficient to stop the enzymatic action irreversibly. Thus the transfer of an enzymatic process developed on laboratory scale into the textile industry should be possible without great delay. 

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