Extraction and bioevaluation of Nigella sativa meal protein isolates in relation to protein enriched cookies

Abstract

Nigella sativa meal is a byproduct obtained after oil extraction that contains appreciable amount of protein. In the current exploration, characterization, extraction and bioevaluation of Nigella sativa meal protein isolates were conducted to develop protein enriched cookies. The protein isolates were prepared through different methods i.e. isoelectric precipitation, micellization and enzymatic extraction. The highest protein yield 79.69±0.70% was estimated in enzymatic protein isolates (EPI) followed by 64.65±0.64% in isoelectric precipitation (IPI) whilst, the lowest output 46.40±0.47% was noticed in micellized protein isolates (MPI). Furthermore, resultant isolates were evaluated for their functional properties. In this context, the highest bulk density was recorded for EPI followed by IPI and MPI. Conversely, the maximum water absorption capacity was observed in IPI trailed by EPI and MPI nonetheless, higher oil absorption was noticed for EPI. The foaming capacity (FC) was highest in IPI followed by EPI and MPI. Likewise, maximum emulsion capacity (60.74± 0.61%) was observed in EPI. The SDS-PAGE depicted that meal protein isolates had protein bands in the range of 6.5 to 116 kDa. Quantification of essential and non-essential amino acid was also carried out with reference profile. Amongst essential amino acids, the maximum lysine content (38.75±0.38 mg/100g) was observed in EPI followed by MPI (34.04±0.34 mg/100g) whilst, IPI had the lowest lysine concentration (29.33±0.29 mg/100g). The protein scores were 65.43, 53.27 & 55.14 for EPI, IPI and MPI, respectively. Additionally, the maximum PDCAAS 82.25±1.56% was noticed in EPI followed by MPI 80.21±1.13% whereas, the minimum scores 73.75±1.54% for IPI during the session 2010-11. Afterwards, bioevaluation trial was carried out through growth and nitrogen balance study parameters. The maximum protein efficiency ratio (PER), net protein ratio (NPR) and relative net protein ratio (RNPR) were observed in EPI followed by IPI and MPI, respectively for the year 2010-11. Similarly, nitrogen balance study parameters expounded the highest true digestibility (TD), biological value (BV) & net protein utilization (NPU) in EPI trailed by IPI. Similar trend for growth and nitrogen balance studies was noticed during the 2 nd year. On the basis of overall yield, functional properties and bioevaluation, one best protein isolate namely EPI was selected for cookies preparation. For the purpose, composite blends were formulated and analyzed for chemical and rheological properties i.e. mixographic and farinographic characteristics. Afterwards, the protein enriched cookies were analyzed for physicochemical characteristics, amino acid profile and hedonic response. On the basis of compiled data for these traits, it is concluded that cookies (T 3 ) prepared by 15% supplementation of enzymatically extracted protein isolates (EPI) of Nigella sativa meal performed better and has potential to address the menace of protein energy malnutrition.