Phytase [myo-inositol(1,2,3,4,5,6)hexakisphosphate phosphohydrolase], a phytate-specific phosphatase, is already used as a supplement in diets for monogastric animals to improve phosphate utilisation from phytate [myo-inositol(1,2,3,4,5,6)hexakisphosphate], the major storage form of phosphate in plant seeds. In recent years, this class of enzymes has also been found increasingly interesting for use in processing and manufacturing of food for human consumption, particularly because the decline in food phytate results in an enhancement of mineral bioavailability. Different strategies could be applied to optimise phytate degradation during food processing and digestion in the human alimentary tract such as adjustment of more favourable conditions during food processing for the phytases naturally occurring in the raw material, addition of isolated phytases to the production process, use of raw material with a high intrinsic phytate-degrading activity either naturally present or introduced by genetic engineering and the use of recombinant food-grade microorganisms as carriers for phytate-degrading activity in the human gastrointestinal tract. Furthermore, phytases may find application in the production of functional foods or food supplements with health benefits. Last but not least, technological improvements are expected to occur due to phytate degradation during processing as shown for breadmaking, production of plant protein isolates, corn wet milling and the fractionation of cereal bran.

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Phytase for food application

Background Rice is a staple food and an important source of proteins in many regions worldwide. Its protein component is generally regarded as hypoallergenic, and a number of studies have highlighted the nutritional and health benefits associated with consumption of rice proteins. In recent years, the processing of plant proteins has drawn scientific and industrial interest, and rice protein-enriched ingredients have become commercially available. Scope and Approach The aim of this study was to provide a critical review of the state of the art regarding the composition, extraction methods, functional properties and applications of rice proteins. Key Findings and Conclusions Rice is composed of four protein fractions, namely albumin (water-soluble), globulin (salt-soluble), glutelin (alkali-soluble), which represents the dominant protein in brown and milled rice, and prolamin (alcohol-soluble), a minor protein in all rice milling fractions. Different methods to extract proteins from rice, including alkaline, enzymatic and physical methods, have been, and continue to be, evaluated for their efficacy, and some have been applied industrially. However, only a limited amount of studies have described the functional properties of rice proteins and how these can be improved by means of enzymatic hydrolysis. Applications of intact rice proteins are limited due to their poor solubility in water. However, hydrolysed rice proteins are used in the formulation of hypoallergenic infant formulas and may potentially be used in a variety of food systems due to their improved functionality. Despite the advances in the characterisation of rice proteins, a greater understanding of their physicochemical properties and how to modify their functionality is required in order to expand their range of food applications.

The composition, extraction, functionality and applications of rice proteins: A review

Vegetable proteins in microencapsulation: a review of recent interventions and their effectiveness

Enzyme assisted extraction of biomolecules as an approach to novel extraction technology: A review.

Rice proteins were extracted from defatted rice flour. Turbidity measurement of supernatants revealed isoelectric points of albumin (pH 4.1), globulin (pH 4.3 and pH 7.9), and glutelin (pH 4.8), at which they were precipitated with 82.3 to 93.2% recovery efficiency. Prolamin did not aggregate and precipitate upon pH adjustment, but was precipitated by acetone. Denaturation temperatures (73.3, 78.9, and 82.2 °C) as well as enthalpy values (2.88, 3.14, and 3.79 J/g), of albumin, globulin, and glutelin were different. Prolamin did not show any thermographic denaturation peak. Heat-denaturation of globulin and glutelin resulted in progressive increases in their surface hydrophobicities. Measurement of surface hydrophobicity would be an effective parameter to evaluate rice protein denaturation.

Extraction, denaturation and hydrophobic properties of rice flour proteins

Rice bran protein isolate (RBPI) containing approximately 92.0% protein was prepared from unstabilized and defatted rice bran using phytase and xylanase. The yield of RBPI increased from 34% to 74.6% through the use of the enzymatic treatment. Nitrogen solubilities of RBPI were 53, 8, 62, 78, 82, and 80% at pHs 2.0, 4.0, 6.0, 8.0, 10.0, and 12.0, respectively. Differential scanning calorimetry showed that RBPI had denaturation temperature of 83.4 degrees C with low endotherm (0.96 J/g of protein). RBPI had similar foaming properties in comparison to egg white. But emulsifying properties of RBPI were significantly lower than those of bovine serum albumin. The result of amino acid analysis showed that RBPI had a similar profile of essential amino acid requirements for 2-5-year-old children in comparison to that of casein and soy protein isolate.

M Wang

Papers

Preparation and functional properties of rice bran protein isolate.