Comparative assessment of natural and synthetic preservatives on shelf stability of spinach smoothies

In the present work, a novel, nutritious food product, a spinach smoothie, was developed. Due to microbial spoilage and quality degradation, the smoothie's limited shelf life was the main issue. For this purpose, natural preservatives (garlic filtrate, ginger filtrate, and a mixture of garlic + ginger filtrate) in comparison to synthetic preservatives (sodium benzoate, citric acid, and a combination of sodium benzoate + citric acid) were added to enhance the shelf life. Further, physicochemical analyses such as pH, specific gravity, antioxidant potential, mineral content, microbial content, and organoleptic properties were evaluated during storage of 28 days. Maximum antioxidant activities for DPPH (41.22 - 32.27%), FRAP (33.21 - 29.35%), TPC (27.11 - 20.84 mg/mL GAE), and vitamin C (31.65 - 27.37 mg/100 mL) were observed with garlic + ginger filtrate smoothie from initial to final day of storage. The highest total bacterial count was observed in the control sample of 30 × 103 - 530 × 103 CFU/mL, and the lowest count was seen in garlic-ginger filtrate smoothie of 12 × 103 - 20 × 103 CFU/mL during the 28-day storage. The maximum score for sensorial acceptability was observed with garlic + ginger filtrate. Therefore, bio-preservatives such as garlic + ginger filtrate at 1% had the highest efficacy level, and were economically suitable. Thus, combining natural preservatives like garlic and ginger with additional nutritional benefits could replace synthetic preservatives.