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- Valorization of rapeseed meal: influence of ethanol antinutrients removal on protein extractability, amino acid composition and fractional profilePublication . Kalaydzhiev, Hristo; Ivanova, Petya; Stoyanova, Magdalena; Pavlov, Atanas; Rustad, Turid; Silva, Cristina L. M.; Chalova, Vesela I.The production of rapeseed oil leads to generation of large quantities of rapeseed meal as a by-product. To increase the applicability of the rapeseed meal in feed and food industries, the content of antinutrient compounds is often reduced by treatment with ethanol. The aim of the study was to evaluate the influence of ethanol pre-treatment of the rapeseed meal on protein extractability, amino acid composition and fractional profile. The ethanol treatment of the rapeseed meal significantly increased the protein content from 37.4 to 42.3% and reduced the lipid concentration from 1.9 to 1.1%. Approximately 4- and 14-fold reductions of the phenols and glucosinolate contents were achieved respectively. Protein yield, however, was diminished from 26.4 to 23.6%. A stronger decrease of the protein yield, from 47.8 to 26.4%, was caused by processing of the rape seeds to rapeseed meal. The process resulted in the reduction of lysine content, while further ethanol treatment of the rapeseed meal affected more amino acids, both essential (threonine, phenylalanine) and non-essential (alanine, tyrosine, arginine, histidine). Comparative fractional protein profiles of rape seeds, rapeseed meal and ethanol treated rapeseed meal exhibited differences in both composition of the fractions and the relative quantity of the proteins. Data suggested that the treatment of the rapeseed meal with ethanol impacted protein solubility, amino acid composition and protein fractional profile. This knowledge is valuable when ethanol treated rapeseed meal is used either as a protein feed additive or as a source for generation of protein-rich ingredients with specific nutritive value and functionality.
- Foaming properties of acid-soluble protein-rich ingredient obtained from industrial rapeseed mealPublication . Ivanova, Petya; Kalaydzhiev, Hristo; Dessev, Tzvetelin T.; Silva, Cristina L.M.; Rustad, Turid; Chalova, Vesela I.The use of the rapeseed meal as a source for preparation of protein-rich ingredients for the food industry is an alternative to the current limited application as a feed additive. The aim of this study was to evaluate foaming properties of an acid-soluble protein-rich ingredient (ASP) obtained from industrial rapeseed meal as a co-product of a protein isolate. Foam capacity and stability over a period of 60 min were evaluated by using volumetric and image analyzing methods. The influence of NaCl at two boundary concentrations (0.03 and 0.25 M) was studied over a pH range from 2 to 10. The ASP exhibited high foamability ([90%), not influenced by pH or salt addition. In contrast, foam stability, measured over a 60 min period, was pH and NaCl dependent. By the end of the observation period, the addition of 0.25 M NaCl reduced the foam volume by more than 70% at all pH values. After 30 min at pH values 4, 6 and 8, which are the most common for food products, the foams without NaCl retained 51, 38 and 41% of the initial foam volume, respectively. The results were in agreement with image analysis observations where microstructure ofthe foams with NaCl was more heterogeneous than that of the foams without salt addition. The high foamability and relatively high foam stability at pH from 4 to 8 without NaCl addition shows that ASP could be a potential alternative to plant proteins currently used as foaming agents in the food industry.