Extraction, optimization, and functional properties of a novel plant protein from kiwifruit (Actinidia chinensis) seeds using ultrasound : a clean and green extraction procedure : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Manawatū, New Zealand
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2022
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Massey University
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The current trend of protein production in New Zealand is primarily focused on proteins sourced from dairy and meat which are known to generate enormous amounts of greenhouse gases and carbon footprints. Thus, to establish a flexitarian world for future sustainability, novel plant proteins from several sources are being recognized and researched lately so that they could replace the meat proteins. One such source of protein are oleaginous plant seeds which are being imagined and explored as a renewable resource of plant proteins worldwide. The oleaginous seeds and seed meals from oil extraction industries, cosmetic industries, and beverage industries related to kiwifruit, represent a significant waste of protein present in these seeds. Moreover, in New Zealand Actinidia Chinensis production, exports and wastage have been increasing manyfold since last decade, as the fruit commodity is shifting from a high-end product to more generalised fruit. Thus, to explore the novel protein in seeds and seed meals of Actinidia Chinensis this study was carried out. Actinidia Chinensis seeds were purchased from Pure ingredients Ltd. New Zealand and were primarily investigated for their physicochemical characteristics to understand the properties of the starting material for the protein extraction process. The seeds were then pulverized, defatted, and analysed for its microstructure and proximate compositions to understand the effect of defatting and grinding on protein contents of defatted seed flour from the Actinidia Chinensis seeds. Further, seed protein was extracted using two different extraction technologies. A clean and green extraction technology; ultrasonication and the conventional stirring method of protein extraction. The results show that ultrasound extraction significantly increased the overall protein yield from the defatted seed flour by 12% if compared to the conventional method. The optimized extraction parameters for the ultrasonic extraction of defatted Actinidia Chinensis seed meal were pH 11.5, temperature 55⁰C, ratio of seed flour to solvent (4:100) and 100 mins of ultrasonic extraction. pH was identified as the most significant factor involved in successful extraction of proteins from kiwifruit seeds whereas temperature and ratio were respectively significant factors after pH. SEM was used to analyze the effects of ultrasonication on the seed meal, seed flour and seed protein extracted from the Actinidia Chinensis seeds. The results confirmed significant effects of fragmentation and cavitation caused by ultrasound waves on seed meal, flour, and protein respectively and increased the protein extraction yield by 12% in this study. The amino acid analysis of seed protein in this study defines a typical acidic profile for Actinidia Chinensis, where glutamic and aspartic acid were the dominating amino acids which defines an acidic profile. the most abundant essential amino acids were Leucine, Lysine and Valine respectively and the least available EAAs were the sulphur AAs such as Cysteine and Methionine. Moreover, in the final sections of this study a few functional properties of the seed protein concentrates are compared with the functional properties of conventionally extracted protein. The results reveal a significant increase in the WHC and OBC of the protein concentrate, whereas the least gelation capacity of the proteins was also positively affected by ultrasonic assisted extraction of kiwifruit seed proteins.
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