Evaluating the Effects of Turmeric and Freezing on the Shelf Stability of Mandazi
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Mandazi is a deep-fried, sweet bakery product with a short shelf life of usually three days when stored at room temperature in a tightly closed container. This is mainly due to factors like spoilage micro-organisms, staling and lipid oxidation. As a result, the mandazi become stale, hard to chew and spoilt which renders them unfit for human consumption. Chemical preservatives have been used to extend the shelf life of bakery products however, there is an increasing demand for more nutritious, functional, preservative-free bakery products with desirable sensory properties and a long shelf life. In this study, alternative approaches to chemical preservatives to prolong the shelf life and maintain the sensory quality of mandazi were investigated namely i.e. spices and freezing. Spices have exhibited anti-oxidant, anti-microbial and anti-staling properties in other bakery products and hence limit the use of chemical preservatives which are perceived as unsafe. This study evaluated the effect of 2% turmeric spice and freezing on the sensory acceptability and shelf stability of mandazi stored at room temperature (25-29oC) and freezing temperature (-27oC). Mandazi were prepared from wheat flour, other selected additives and packaged in polyethylene bags. Stored mandazi were analyzed at intervals for sensory acceptability, thiobarbitoric acid (TBA) index, yeasts and moulds during a storage period of 30 days. The combination of turmeric and freezing inhibited the growth of moulds and yeasts in mandazi throughout the storage period of 30 days. Also, sensory results indicated that no significant differences in acceptability were observed between different mandazi samples with and without turmeric. Freezing maintained the sensory acceptability of the mandazi throughout the storage period and the sensory acceptability scores were still high even on the final day of storage with no significant difference from the initial acceptability. The TBA values for all the mandazi samples were very low i.e. between 0.03 – 0.12mg/kg throughout the storage period; indicating that no mandazi went rancid during the 30-day storage period. Mandazi with no turmeric and kept at room temperatures exhibited higher TBA values. This study showed that turmeric and freezing can be used to maintain the sensory acceptability and prolong the shelf life of mandazi from 3 days to more than 4 weeks.