Abstract
The aim of this study was to develop an extraction method to produce highly functional oat protein concentrates. We investigated the possibility of combining enzyme-aided slightly alkaline (pH 8.0) extraction with ultrafiltration and subsequent diafiltration for concentration of the extracted oat proteins. A further aim was to study how the deamidation of oat proteins with protein-glutaminase (PG) improves the solubility of proteins as a function of the following parameters: pH (6.0–9.0), enzyme dosage (4–20 U/g protein), and incubation time (1–4 h) with response surface methodology (RSM). Furthermore, we investigated selected functional properties, such as heat-induced gelation and solubility, of the oat protein concentrates. The chosen parameters for the enzymatic deamidation pre-treatment process by PG were as follows: pH 8.0, dosage 11.0 U/g protein, and an incubation time of 4 h (1 h at native pH and 3 h at pH 8.0). Two oat protein concentrates were produced, non-deamidated and ultrafiltered, and deamidated and ultrafiltered, with protein concentrations of 45.0 and 52.4%, respectively. The solubility of both oat protein concentrates was significantly improved at neutral and slightly alkaline pH compared to the solubility of proteins extracted from the starting material. Additionally, both oat protein concentrates produced equally strong heat-induced gel-like structures at a protein concentration of 10%.
Highlights
Oat (Avena sativa L.) is an interesting cereal due to its higher protein content compared to the other cereals such as wheat, barley, and rye [1]
This study aimed to develop an extraction method for producing oat protein concentrates with improved techno-functional properties; as well as the possibility of combining enzyme-aided slightly alkaline extraction with ultrafiltration and subsequent diafiltration for the concentration of the extracted oat proteins
The response surface methodology (RSM) method data was obtained from 17 design points, with three independent variables and the corresponding responses, deamidation degree (DD) and protein solubility (PS) (Table 1)
Summary
Oat (Avena sativa L.) is an interesting cereal due to its higher protein content compared to the other cereals such as wheat, barley, and rye [1]. The distribution of proteins in the layers of oat groats is as follows: 12% protein in the starchy endosperm, 18–30% in the bran, and 29–38% in the germ [2,3]. Oat globulin proteins are primarily situated in the starchy endosperm in the protein bodies and in the aleurone layer. The second most abundant protein group is the prolamins (avenins), which account for 4–15% of the total protein [4,5]. Another minor protein group in oats is the water-soluble albumins. Their proportion of the total protein varies depending on the oat source (cultivars), growth conditions, and extraction method
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