Effects of modified atmosphere packaging and preservatives on the shelf-life of high moisture prunes and raisins

The growth of Aspergillus niger and Zygosaccharomyces rouxii on high moisture prunes and raisins in the presence of preservatives and packed under modified atmospheres was determined. Prunes and raisins adjusted to an a(w) of 0.84-0.87 in the presence of carbon dioxide atmospheres (40 and 80% CO₂) did not support growth of A. niger. However, Z. rouxii spoiled the fruit samples, both in air and under CO₂ conditions. Addition of low levels of K-sorbate (186 ppm in prunes and 153 ppm in raisins) or Na-benzoate (176 ppm in prunes and 158 ppm in raisins) delayed outgrowth of Z. rouxii. The inhibitory effect of preservatives was higher in raisins than in prunes. Modified atmospheres (40% CO₂-60% N₂ or 80% C0₂-20% N₂) combined with the addition of 417 and 343 ppm K-sorbate or 383 and 321 ppm Na-benzoate accomplished complete growth inhibition of Z. rouxii and extended the shelf-life of high moisture prunes and raisins at 30°C for at least 6 months.