Valorization of Food Waste for Biosynthesis of Single Cell Protein

Abstract

There is high prevalence of nutrient deficiencies especially protein energy malnutrition in Pakistani population. Present research project was aimed to produce protein from non conventional source and its utilization in food products. In this regard, different food wastes including potato peel, banana peel, orange peel, carrot pomace and sugar beet bagasse were used as substrate for single cell protein (SCP) production from Saccharomyces cerevisiae. Proximate composition showed the significant differences between various chemical constituents (crude fat, crude protein, crude fiber, ash, carbohydrates) of these food wastes. SCP production process was optimized by fermentation of these food wastes at various temperature (20ºC, 30ºC, 40ºC, 50ºC, 60ºC) for different time duration (1, 2, 3, 4, 5, 6 and 7 days) with the supplementation of nitrogen sources (Urea, Corn steep liquor, Ammonium Sulfate, Ammonium nitrate and Sodium nitrate) Results revealed that maximum amount of SCP (11.7 ± 0.58g) was produced when Saccharomyces cerevisiae was cultured at potato peel supplemented with 1% ammonium sulfate at 30°C for six days. The SCP contained crude protein, crude fat, crude fiber, ash contents and NFE (carbohydrates) 47.78 ± 2.39, 2.34 ± 0.11, 3.42 ± 0.17, 7.9 ± 0.4 and 38.56 ± 1.93%, respectively. Furthermore, amino acid profile indicated SCP as a rich source of essential and non-essential amino acids. Amongst essential amino acids (g/kg), the highest value was noted for leucine (43.5 ± 0.21), followed by valine (38.3 ± 0.19), lysine (31.4 ± 0.15) and phenylalanine (26.9 ± 0.13). Similarly, aspartic acid (39.0 ± 0.19 g/kg) was the dominant non-essential amino acid followed by arginine (32.1 ± 0.16g/kg). Likewise, functional properties including bulk density (0.53 ± 0.02 g/cm3 ), water absorption capacity (2.10 ± 0.1 mL/g), oil absorption capacity (1.72 ± 0.08 mL/g), foaming capacity (10.49 ± 0.5%), foaming stability (17.4 ± 0.8%), emulsion activity (52.36 ± 2.6%), and emulsion stability (70.54 ± 3.5%) were exhibited by SCP. Afterwards, wheat flour was enriched with different concentration of SCP (4, 8, 12, 16 and 20%). Results revealed positive increase in the nutrients of wheat flour upon incorporation of SCP at different levels. Similarly, functional properties of SCP fortified wheat flour were also improved. Besides, cookies and noodles were prepared from SCP enriched wheat flour and evaluated for different quality parameters. Physical parameters of cookies showed decrease in diameter, spread ratio and hardness upon SCP incorporation. However, thickness of SCP enriched cookies was increased. Likewise conducting color analysis, SCP enriched cookies tend to be more red compared to control. Overall, cookies with 12% SCP incorporation got maximum score (8.39 ± 0.1) from judges due to appealing color, rich taste, smooth texture and mouthfeel. Similarly, noodles exhibited decreased cooking time and increased yield upon SCP enrichment. Likewise, nutritional parameters of noodles including ratio of essential amino acids to total amino acids (48.46 ± 2.42%), essential amino acid index (134.9 ± 6.74%), biological value (135.31 ± 6.7%) and protein efficiency ratio (10.82 ± 0.54%) were improved with SCP enrichment. However, noodles with 8% SCP enrichment got maximum score from sensory panel. In short, results revealed that SCP production on food waste is a sustainable approach and can be utilized in various food products for protein enrichment and improve nutritional and organoleptic properties.