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.

Effect of Addition of Coffee Extract on Physicochemical and Sensory Properties of Yoghurt

“…The pH values for all the samples in this study was less than 4.5 hence they met the FDA (Food Drug Administration) specifications for yoghurt of a maximum pH of 4.5 [6]. Low pH values in yoghurt makes calcium present in milk more bioavailable for absorption in the intestines through its conversion into its ionic form [6].…”

“…This is because of post acidification facilitated by the LABs in the yoghurt through breakdown of lactose to yield lactic acid acetaldehyde, esters and carbon dioxide thus lowering the pH [16], [17]. The pH values for all the samples in this study was less than 4.5 hence they met the FDA (Food Drug Administration) specifications for yoghurt of a maximum pH of 4.5 [6]. Low pH values in yoghurt makes calcium present in milk more bioavailable for absorption in the intestines through its conversion into its ionic form [6].…”

“…The breakdown of lactose into lactic acid, acetaldehyde and other derivatives improves the organoleptic characteristics of yoghurt. This fermentation process lowers the pH and raises the titratable acidity of the yoghurt thus making calcium more bioavailable and easily assimilated into the body [6]. This also increased the intake of the yoghurt by the lactose intolerant people as well as lengthening the shelf life of milk [7].…”

“…This also increased the intake of the yoghurt by the lactose intolerant people as well as lengthening the shelf life of milk [7]. The physicochemical properties such as pH, titratable acidity, syneresis and viscosity influence the sensory characteristics of yoghurt [5], [6]. Syneresis is the separation of whey protein from the gel matrix of casein micelles interfering with the viscosity of the yogurt.…”

“…The pH was determined by the method described by [6], where 10g of the sample was dissolved in 100 ml of distilled water. The mixture was allowed to equilibrate for 3 minutes at room temperature.…”