Production of protein concentrate and isolate from cashew (<i>Anacardium occidentale L.</i>) nut

Abstract

The study evaluated methods of producing protein concentrates and isolates from cashew nut in order to increase the global utilization of cashew nut and increase the availability of affordable, good quality protein for people. Cashew nuts were processed to obtain roasted cashew kernel. The roasted cashew kernels were processed into powder by cold solvent extraction of the fat in the cashew meal. Proximate composition of the cashew nut and meal were determined to ascertain the protein content of the cashew nut. The extraction of the proteins was done using two different methods based on the known methods of production of protein isolate and concentrate from other plant sources (peanut), since there are no familiar methods for the production of protein isolate and concentrate from cashew nut. The protein isolates were obtained by an alkaline extraction-isoelectric precipitation method, which involved aqueous alkaline extraction of the proteins at low temperature, and isoelectric precipitation of the protein fractions; the protein concentrates were obtained using an alkaline extraction-methanol precipitation method, which involved aqueous alkaline extraction of the proteins at low temperature, and alcoholic precipitation of the protein fractions. Extraction ratios of 1:5 and 1:10, extraction pH of 7.0 and 9.0, and isoelectric precipitation at pH of 3.5 and 4.5 were used to obtain eight cashew protein fractions of different protein contents (44.4 to 99.8%) and different protein yields (48.3 to 98.9%) from the use of the isoelectric precipitation methods. Similarly, using the methanol precipitation method, extraction ratio of 1:5 and 1:10, pH of 7.0 and 9.0, and concentrations of methanol of 70% and 80%, were used to obtain eight cashew protein fractions of varying protein contents (64 to 89%), and protein yields (52.1 to 88.2%). Protein contents of the cashew protein fractions were determined using 2-D Quant kit method, while the protein yields were calculated using the weight of the protein fractions obtained from the cashew meal of known weight. From the results of the protein content analysis of the protein fractions and according to the CODEX Standard, it was demonstrated that, cashew nut protein isolate (99.8% protein content), and, cashew nut protein concentrate of varying protein contents could be obtained from the isoelectric precipitation method, while only protein concentrate was obtained using the methanol precipitation method.

Key words: Cashew Nut, Protein, Isolate, Concentrate