Evaluating the Effect of Vacuum Packaging and Freezing on the Shelf Stability of Mandazi

Abstract

Mandazi is a form of sweet fried bread consumed as a snack. Mandazi has great economic and nutritional importance and originates from East Africa. Mandazi have a short shelf life of a few days when stored at room temperature. Spoilage in mandazi is caused by fungal and bacterial growth, oxidative rancidity, and staling. Spoilage causes deterioration in product organoleptic properties which lower consumer acceptability and cause health risk. In this study, vacuum packaging and freezing were investigated as alternatives to the use of chemical preservatives to prolong the shelf life and maintain the sensory quality of mandazi. Using experimental design, mandazi samples were randomly packaged in either vacuum packaging or polyethylene bags, and randomly assigned to either storage at room temperature (25-29 °C) or frozen storage at -27 °C. Samples were stored for a period of 30 days and analysed at intervals for sensory acceptability, yeasts and moulds counts, and thiobarbituric acid (TBA) index. No significant differences were observed between sensory acceptability of mandazi samples in vacuum packaging and polyethylene bags. Samples stored at freezing temperature maintained high sensory acceptability throughout the 30 days without significant reduction. The willingness to buy scores for the samples correlated with the acceptability of the samples. The combination of vacuum packaging and freezing prevented the growth of moulds and yeasts in mandazi throughout the storage period. Mandazi stored at room temperature had high yeast and mould counts (from 3 log cfu to 5.1 log cfu) throughout the study period. All the samples had very low thiobarbituric acid (TBA) values (between 0.03 – 0.12 mg/kg) throughout the storage period; indicating that samples did not become rancid. Samples stored at room temperatures had higher TBA values than those subjected to freezing throughout the storage period. This study showed that a combination of vacuum packaging and freezing can be used to maintain the sensory acceptability and prolong the shelf life of mandazi to more than 30 days.