Effect of optimised infrared heat treatment on composition structure and gelation properties of cowpea protein isolate.

Abstract

Infrared radiation heating is a heat pre-treatment method that employs infrared electromagnetic radiation to generate heat in pulses such as cowpea for the production of instantized ingredients and products. Optimum processing conditions, moisture content of 45%, the heating temperature of 185 „ƒ, and time of 5 min was reported to precooked cowpea from previous studies. Modified protein isolates are suitable for industrial use due to their improved functionality. In this study, the effect of optimised conditions (45% moisture, the heating temperature of 185 „ƒ, and heating time of 5 min) on the composition structure and gelation properties of protein isolated from cowpea seed was investigated. This was then analysed by amino acid profiling, hydrophobicity, FTIR and Intrinsic fluorescence emission in comparison with the untreated to define its potential application in the food system. Aspartic acid and glutamic acids were the major amino acids in the protein isolates from the optimised infrared heated cowpea compared to the untreated cowpea. Infrared heating induced a slight blue shift from 350 nm in the untreated cowpea to 347nm in the treated cowpea protein isolates indicating a more folded structure in the protein. This coincides with the hydrophobicity data. Particle size data revealed that the optimised infrared heated cowpea protein isolate body has multimodal particles while the untreated isolated cowpea protein has a bimodal particle size. The polydispersity index (PDI) of the infra-heated cowpea is below 0.3 indicating a homogenous particle size within the protein body. the β-sheet structure was dominant in both treated and untreated cowpea protein isolates. The dispersion of treated cowpea protein formed a structured network fluid. Infrared heating may improve the functional application of cowpea protein in industries.