Proximate, physicochemical and sensory evaluation of jam produced from black plum (Vitex doniana) fruit at different stages of maturity

Abstract

This study examined the suitability of black plum (Vitex doniana) fruit for jam production using different proportions of ripe and unripe fruits. Three jam formulations were prepared: 100% ripe fruit jam (RHJ), 60% ripe and 40% unripe fruit jam (RSJ), and 40% ripe and 60% unripe fruit jam (RFJ). The jams were produced and subjected to physicochemical, proximate, and sensory analyses using standard methods. Results showed that increasing the proportion of unripe fruit significantly increased titratable acidity, pectin content, and viscosity, while reducing sugar content and total soluble solids. RFJ exhibited the highest pectin content (8.91%) and viscosity (87.47 dynes/cm²), whereas RHJ recorded the highest reducing sugar content (54.41%) and total soluble solids (68.85 °Brix). Pectin improved the viscosity and acceptability of the jam. Similarly, the Brix and reducing sugar content increased with a higher percentage of ripe fruit, while the commercial jam (SBJ) recorded the highest Brix and reducing sugar contents. Sensory evaluation revealed that black plum jam compared favourably with commercial black currant–strawberry jam in taste and mouthfeel, while achieving superior aroma scores. However, overall acceptability was slightly lower due to the darker colour of the black plum jam. The findings demonstrate that black plum possesses adequate natural pectin and desirable sensory characteristics for jam production and represents a promising strategy for reducing post-harvest losses, as well as promoting the utilization of this underexploited indigenous fruit. Thus, further improvement in colour, formulation balance, storage stability, and shelf-life assessment is recommended.