6533b860fe1ef96bd12c2d2e

RESEARCH PRODUCT

effect of the extraction of proteins from hemp press-cakes on their functionalities

subject

description

Plant proteins are a coherent option to feed the planet while limiting global warming. Common proteins (wheat, soya and maize) will soon no longer be sufficient to meet the increased demand for proteins. This thesis focuses on the development of a new source of plant protein for human consumption, based on a co-product of the oil mill: hemp proteins from press-cake. To meet this objective, the three main lines of action are: the definition of extraction conditions, the study of the physico-chemical properties of the isolates extracted under the defined conditions and the study of their emulsifying properties. The data in the literature on the extraction of hemp proteins are limited and not very detailed. Proteins are generally extracted from solvent-delipidated press-cake by alkaline solubilization (pH 10), isoelectric precipitation (pH 5), neutralization (pH 7) and freeze-drying. These protein isolates appear to have low solubilities over a wide pH range, probably due to strong interactions between proteins at the isoelectric point that insolubilize some of them. The extraction desired in our study is an extraction from raw press-cake (without solvent), without isoelectric precipitation and allowing globulins and albumins to be extracted simultaneously. The impact of extraction conditions on the quality and quantity of extracted proteins is determined. The hydration conditions studied are different pH (2 to 12), ionic strengths (0 to 500 mM NaCl) and weight ratios of press-cake/water (2 to 22%). The effects of an ultrafiltration purification step and the drying method (spray or freeze-drying) are also studied. Only alkaline pH ≥10 allows the simultaneous extraction of globulins and albumins with yields ≥40%. On the other hand, such pH values also solubilize phenolic compounds that can form complexes with proteins. A diafiltration step by ultrafiltration is necessary to increase protein purity to more than 80% and spray-drying does not seem to be denaturing. Extraction at pH 10 produces native proteins. In their raw state, they show good emulsifying properties. Thermal denaturation greatly reduces their emulsifying properties. Extraction at pH 12 denatures proteins, certainly due to a high surface charge that induces their unfolding. Aggregates probably involving phenols via covalent bonds are formed. However, the solubility of these proteins as well as their emulsifying properties are better than those of proteins extracted at pH 10. Through this manuscript we discussed and tried to understand the differences observed between the proteins extracted at pH 10 and pH 12.