Quality characterization of bread retailed in Nairobi County, Kenya: Physico-chemical and microbial profiles

Abstract

With the ever-increasing intake and diversification of bread in sub-Saharan Africa, greater risks of food fraud are posed. The risks are even higher in the urban areas where both the formal and informal retail exist. Product diversification induced by incorporation of different ingredients in bread processing aggravates the risk of malpractices in processing that is evidenced in product quality. The current study employed a cross-sectional survey of bread retailed in the fourteen supermarkets located in Nairobi County, Kenya to determine their physico-chemical and microbiological characteristics. The study showed that brown bread had significantly (p<0.001) higher moisture and water activity, although the fibre and total solids in the brown bread were significantly (p<0.01) lower than the white bread. The greatest variability in the physico chemical attributes was found in the acid insoluble ash, with a coefficient of variation of 82.04%. The highest proportion of the bread, 58.9%, fell short of meeting the regulatory stipulations of the acid insoluble ash. Significantly (p<0.05) higher proportion of the brown bread (60.7%) than the white bread (4.4%) had crude fibre contents less optimal than the regulatory stipulations. The greatest adherence to product quality stipulations was found in yeast and mould counts (100%), moisture content (99.1%) and pH aqueous extract (95.5%). Both the brands of bread and retail outlets had quarter of them recording higher moisture, water activity and total acid insoluble ash than the averages of breads traded in supermarkets; whereas the pH, fibre and total solids were lower (kmean clusters=2). Eight principal components maximally explained product variability in the breads, with similar trends of composition between moisture and protein, and fibre and total solids, whereby the latter pair had a negative correlation with the former. In conclusion, the study found that the formal sector still falls short of product quality regulatory stipulations, pointing to greater need to strengthen surveillance component of food control for this sector.