Abstract
Extraction of proteins from defatted sunflower meal has been improved by addition of the protease alcalase during alkaline extraction. This method offers several additional advantages as compared to the traditional alkaline extraction without alcalase, which is usually carried out after a sedimentation/flotation step to remove the lignocellulosic fraction. As compared to extraction without alcalase, addition of 0.1% (v/v) alcalase improved the yield of protein extraction from 57.5% to 87.4%, providing an extract that is 22% hydrolyzed. In addition, an increment of up to 4.5 times in protein solubility at low pH values is achieved, which correlates with the degree of hydrolysis. The extracts that were obtained in the presence of alcalase had a higher proline and glycine content, suggesting that the protease improves extraction of proline-rich and glycine-rich cell wall proteins that are part of the lignocellulosic fraction. These protein extracts can be directly dried without generation of wastewater, and the resulting fiber-rich material could be used for animal feeding.
Highlights
The transformation of by-products of the food industry into new, non-conventional sources of proteins is of great interest because it represents a potential source of inexpensive protein for feeding livestock and for human consumption
Defatted sunflower meal, which contains about 30% protein (Parrado et al, 1991), has already been used for the preparation of protein isolates (Saeed & Cheryan, 1988) and high added-value protein hydrolysates (Villanueva et al, 1999)
It has been observed that a limited treatment of Brassica carinata defatted meal with alcalase produces a significant increase in the yield of protein extracts (Pedroche et al, 1998)
Summary
The transformation of by-products of the food industry into new, non-conventional sources of proteins is of great interest because it represents a potential source of inexpensive protein for feeding livestock and for human consumption. It has been observed that a limited treatment of Brassica carinata defatted meal with alcalase produces a significant increase in the yield of protein extracts (Pedroche et al, 1998). Since treatment with alcalase appears to enhance protein extraction from different sources, the effect of adding alcalase during extraction of defatted sunflower meal protein has been investigated. Alkaline extraction in the presence of alcalase has been compared with the conventional method for alkaline extraction in the absence of alcalase. This results in several advantages, in addition to allow high yields of protein extraction without having to carry out a preliminary flotation/sedimentation step to remove the lignocellulosic fraction
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