Proteins for foods, in addition to providing nutrition, should also possess specific functional properties that facilitate processing and serve as the basis of product performance. Functional properties of proteins for foods connote the physicochemical properties which govern the behavior of protein in foods. This general article collates the published information concerning the major functional properties of food proteins, e.g., solubility, binding properties, surfactant properties, viscogenic texturizing characteristics, etc. The effects of extraction and processing on functional properties and possible correlations between structure and function are discussed, in relation to practical performance in food systems. Modification of proteins to improve functional characteristics is briefly mentioned.

Functional properties of proteins in foods: A survey

Soy protein ingredients must possess appropriate functional properties for food applications and consumer acceptability. these are the intrinsic physicochemical characteristics which affect the behavior of protein in food systems during processing, manufacturing, storage and preparation, e.g., sorption, solubility, gelation, surfactancy, ligand-binding, and film formation. These properties reflect the composition and conformation of the proteins, their interactions with other food components, and they are affected by processing treatments and the environment. Because functional properties are influenced by the composition, structure and conformation of ingredient proteins, systematic elucidation of the physical properties of component protein is expedient for understanding the mechanism of particular functional traints. The composition and properties of the major components of soy proteins are summarized, and the functional properties of soy proteins of importance in current applications (e.g., hydration, gelation, emulsifying, foaming and flavorbinding characteristics) are briefly reviewed.

Functional properties of soy proteins

Aqueous and enzymatic processes for edible oil extraction

A comprehensive review of the literature about use of solvents for extraction of oilseeds is presented. Mention has been found of over 70 solvents. Currently, hexane is the major solvent in use, but recent price increases and safety, environmental and health concerns, have generated interest in alternatives. Solvents vary considerably in chemical and physical properties which affect their performance in oil extraction. The choice of solvent depends upon the primary end product desired (oil or meal). Recent research on alternative solvents has focused on ethanol, isopropanol, methylene chloride, aqueous acetone, and hexane/acetone/water mixtures.

Comparison of alternative solvents for oils extraction

G. Reed, Introduction. K.L. Parkin, General Characteristics of Enzymes. K.L. Parkin, Environmental Effects in Enzyme Activity. J Wegstein, Modern Methods of Enzyme Expression and Design. P. Aldercreutz, Immobilization. R. Bigelis, Carbohydrates. J. Adler-Nissen, Proteases. S.E. Godtfredsen, Lipases and Esterases. F. Hammer, Oxidoreductoses. T. Szakucki, Application of Oxidoreductases. B. Sproessler, Milling and Baking. R.E. Hebeda, Starches, Sugars, And Syrup. R.J. Brown, Dairy Products. W. Pilmik, Pectic Enzymes in Fruit and Vegetable Juice Manufacture. T. Nagodawithana, Flavor Enhancers. J.-C. Villettaz, Wine. J. Power, Beer. D. Bernnachi, Enzymes for Meat Tenderization. G. Stafansson, Fish Processing.

Enzymes in Food Processing

Oil can be removed from oilseed materials by a process which consists of an aqueous extraction of the comminuted seed, followed by a centrifugal separation which divides the aqueous extract into oil, solid, and aqueous phases. The protein may be recovered in the solids or aqueous phase, depending upon the conditions selected. Unit operations of this process are grinding, solid-liquid separation, centrifugation, demulsification, and drying of products. Aqueous extraction has been applied, to date, to coconuts and peanuts. For coconuts, a procedure has been developed to recover 93% of the oil and 91% of the protein. The major protein product is 25% protein and, when reconstituted in water, forms an acceptable beverage. The estimated production cost of this product is $.24/1b. For peanuts, the recovery of oil was 89% and protein 92% for the concentrate procedure, whereas the corresponding values for the isolate procedure were 86% and 89%, respectively. The costs of production were estimated as $.17/1b of concentrate (67% protein) and $.28/1b of isolate (89% protein). Aqueous extraction offers several advantages over conventional solvent extraction-less initial capital investments, safer operation, capability of discontinuous operation, and production of a variety of products. Another advantage of aqueous processing is the capability for utilization of certain chemicals to remove or inactivate undesirable substances. In the case of peanuts, hydrogen peroxide and sodium hypoehlorite have proven to be effective for destruetion of aflatoxins. Aqueous processing has the potential for application to a variety of other oilseeds.

Aqueous extraction—An alternative oilseed milling process

Aqueous processing of fresh coconuts for recovery of oil and coconut skim milk

An aqueous process was investigated for the recovery of oil and food grade protein from fresh coconuts. Efficient recovery of oil, which is very important for economical reasons, was related to three critical unit operations: separation of oil from the fiber, destabilization of an oil-in-water emulsion, and recovery of a protein product that is low in oil content. The material balance is reported for a laboratory process that satisfactorily separates oil and breaks the emulsion, and data are shown which has led to a process for recovery of a protein with low oil content.

Critical unit operations of the aqueous processing of fresh coconuts

Water binding of some purified oilseed proteins

The shell of coconuts contained large populations of various microbial types. Acinetobacter, Enferobacteriaceae, Flavobacterium, Micro-bacterium, Micrococcus species and yeasts and molds predominated. Aseptically removed meats or water of high-quality undamaged coconuts, contained few of no microorganisms. Spray-dried and intermediate moisture products prepared from coconut skim milk contained low levels of viable microorganisms (3,100–13,000, mean 6,600/g). Bacterial counts of these products changed little during storage for 90–120 days at either 21 or 35°C. No increase in population took place at 35°C for 25 days when five microbial species were inoculated individually into an intermediate moisture product with a moisture level of 30.7%.

Robert Hagenmaier

Papers

Aqueous extraction—An alternative oilseed milling process

Aqueous processing of fresh coconuts for recovery of oil and coconut skim milk

Critical unit operations of the aqueous processing of fresh coconuts

Water binding of some purified oilseed proteins

Microbiological evaluation of coconut and coconut products