Influence of Ocimum gratissimum (Scent Leaf) on the Organoleptic Acceptability and Shelf Stability of Yoghurt

Abstract

Aim: To investigate the preservative efficiency of Ocimum gratissimum or its extracts on yoghurt. Study Design: Ten yoghurt samples were prepared, furthermore, nine (9) samples were treated with scent leaf in different forms at different concentrations. Place and Duration of Study: Department of Food Science and Technology, Nnamdi Azikiwe University, Awka, Anambra State, Nigeria, between September 2015 and June 2016. Methodology: Yoghurt was prepared from instant filled milk while Direct Vat Inoculum (DVI) was used as the starter culture. Proximate and phytochemical analyses were carried out following standard procedures. Sensory evaluation was carried out using a 15-man panelist with a seven point hedonic scales and results were statistically analyzed using IBM® SPSS 21.0, at 0.05 probability level. pH and microbial analysis were conducted while bacterial characterization involved biochemical tests and isolation of probable microorganisms employed morphological and structural characteristics. Results: Result for proximate analysis indicated differences in the nutritional composition of the raw milk and yoghurt (control). Moisture content increased considerably from 10.00% to 69.75%, while a reduction in protein content was reported (8.7% - 4.95%). The lipid content classified the produced yoghurt as a low-fat yoghurt, and expectedly, the carbohydrate content reduced from 58.20% - 22.30%. Phytochemical screening of the different forms of scent leaf indicated the presence of alkaloids, flavonoids, saponins, cardiac glycosides, and steroids, in different concentrations. Sensory scores showed that the panelists preferred yoghurt formulated with 3 mL of squeezed scent leaf extract. pH values decreased with storage period, while microbial load ranged between 0.5× 104 – 2.0 × 104, where Klebsiella spp., Streptococcus spp., E. coli, Bacillus, S. aureus, Pseudomonas spp., Enterobacter, and Proteus spp. were isolated. Conclusion: The yoghurt samples formulated with squeezed scent leaf extracts had the best organoleptic acceptance, while the sample treated with 3 mL had the lowest microbial load, hence, it can be inferred that the squeezed scent leaf extracts had the best preservative effect.