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Studies on the preparation and characterization of protein hydrolysates from groundnut and soybean isolates

Govindaraju, K. (2003) Studies on the preparation and characterization of protein hydrolysates from groundnut and soybean isolates. Doctoral thesis, University of Mysore.

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Abstract

Proteins are important in food processing and food product development, as they are responsible for various functional properties that influence consumer acceptability. Both animal and plant proteins are used commercially as functional ingredients. Plant proteins are the most abundant in the world. A number of vegetable proteins have been tried for incorporation in various food products as functional and nutritional ingredients. Oilseed protein products are rapidly gaining importance in protein supplementation because of their unique functional properties. The intrinsic properties of proteins like the amino acid composition and conformation of the proteins, methods and conditions for their isolation,degree of purification and processing alterations are some of the important factors that influence the functional properties of food proteins. Various approaches like chemical modification, physical treatments and enzymatic modification have been tried to improve functional characteristics of proteins. Chemical modifications such as succinylation,acetylation and mild alkali hydrolysis have been reported to improve the functional properties. One of the major drawbacks of these approaches is the deterioration of the nutritional quality owing to the blocking or destruction of essential amino acids. One of the important ways to enhance the functional properties of oilseed proteins is enzymatic modification. Enzymatic modification occur under mild conditions retaining nutritional value and offer a convenient means for improving functional properties of proteins. By controlling the extent of hydrolysis it is possible to enhance various functional properties to develop new functional ingredients to fabricate new food analogs simulating traditional foods. Protein hydrolysates find application in special foods such as those designed for children, old people, athletes and also in pharmaceutical preparations developed for convalescents and those who suffer from digestive disorders. Foods based on highly hydrolysed proteins are useful in controlling food allergies. The major ways of supplying tailored amount of amino acids are i) enzymatic protein hydrolysates and ii) a mixture of synthetic amino acids. They are preferred over synthetic amino acids at moderate cost because of availability on commercial scale and high quality of enzyme hydrolysed products. Enzymatic protein hydrolysates containing short chain peptides with defined amino acid composition and molecular size are preferred for specific formulations. These protein hydrolysates score over elemental diets in which the protein component consists exclusively of a mixture of free amino acids. The short chain peptides are absorbed preferentially over free amino acids in the gut. Protein hydrolysates offer as an alternative to intact proteins and elemental formula in the development of special formulations designed to provide nutritional support. Soybean and groundnut are the most widely cultivated oilseeds all over the world. Dehulled soybean contains 17-18% oil and 25-35% protein depending on the variety. Similarly, dehulled groundnut depending on the variety contains 50-60% oil and 30-35% protein. Defatted soybean flour contains 50-55% protein of good nutritional quality. Soybean proteins are rich in lysine and deficient in methionine. The major intrinsic anti nutritional factor is trypsin inhibitor, which affects its utility. Groundnut proteins are deficient in lysine and methionine. The protein digestibility corrected amino acid score for soy protein and groundnut protein is 0.92 and 0.52 respectively. The protein ingredients such as defatted flour,protein concentrate and protein isolates from these sources have a good potential for preparing speciality foods under native and modified conditions. The protein hydrolysates obtained from these sources can effectively replace commercially available milk protein hydrolysates because of their good nutritional quality. In general, oilseed proteins offer resistance to enzymatic hydrolysis. Studies on hydrolysis of pure proteins would help in understanding of the various structural features of the protein both at surface and subunit levels. Though the resistance to hydrolysis of seed proteins by enzymes is well documented, work on the relative effectiveness of the major proteins with different proteolytic enzymes is less. Glycinin and conglycinin are the major fractions of soybeans and make up to 70% of the total proteins. Arachin and conarachin are the major fractions, which make nearly 80% of the total groundnut proteins. The individual roles of major protein fractions are important in order to understand the overall functional profile of the total proteins and protein ingredients. Glycinin is poorer in functional properties compared to conglycinin. This has been attributed to the compact structure of the high molecular protein fraction in which hydrophobic groups are buried inside. The functional properties of protein isolates and isolated fractions can be modified either by chemical means or enzymatic hydrolysis. Although sufficient information is available on the enzymatic modification of soybean or groundnut flour and its effect on functional properties, the information on the controlled hydrolysis of major globulins of oilseeds are limited. In this work, protein hydrolysates from soybean and groundnut were prepared using different proteolytic enzymes starting with different materials like defatted meal, protein isolates and purified fractions. With the use of different enzymes and by varying the experimental parameters like E/S ratio, pH, temperature and combinations of proteolytic enzymes, it was possible to tailor the functional characteristics of various protein hydrolysates. Attempt has also been made to correlate various functional characteristics with some of the biophysical and biochemical parameters.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: Oilseed protein products Protein hydrolysates Soybean groundnut enzymatic protein hydrolysates
Subjects: 500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 29 Protein Chemistry
600 Technology > 08 Food technology > 22 Legumes-Pulses > 03 Peanut
600 Technology > 08 Food technology > 22 Legumes-Pulses > 05 Soya bean
Divisions: Protein Chemistry and Technology
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 03 Dec 2007 05:30
Last Modified: 09 Apr 2018 11:11
URI: http://ir.cftri.com/id/eprint/1524

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