Quality and shelf life of calcium-enriched wholemeal bread stored in a modified atmosphere

Calcium-enriched wholemeal bread packed in a modified atmosphere (60% CO₂, 40% N₂), was examined for stability and microbiological changes throughout 32-day storage. The product was still acceptable after 24 days at 20 ± 1 °C. At this time no microbiological changes were observed; however, there was a continuous decline in sensory quality, mainly due to deterioration of the texture. Crumb hardness increased, whereas its springiness and cohesiveness decreased. These observations were accompanied by physical and chemical changes characterized by a steady increase in acidity and a sharp decrease in blue value, especially at the beginning of storage. The first microbiological changes occurred only after 27 days of storage and were due to the growth of moulds and amylase-negative Gram-positive cocci, cocci-bacillus or bacillus. The principal component analysis showed that nearly 86% of the variance in ten considered variables could be represented by two new variables: PC1, defined by eating quality and physicochemical attributes, and PC2 defined mainly by chewiness. Three groups of stored bread were identified on the score plot. The first group, fresh and 3-day stored bread, was characterized by low hardness and sourness; the second, bread stored from six to twenty days, scored lower for overall sensory quality, low springiness, cohesiveness and blue value; and the third group, the product during the final stages of storage, exhibited a clear increase in chewiness and hardness and showed the first indications of microbial deterioration.