Microbial spoilage of date rutab collected from the markets of Al-Hofuf city in the Kingdom of Saudi Arabia.

Microbial spoilage was monitored in 520 samples of dates in the rutab stage purchased from retail outlets in Al-Hofuf City, Saudi Arabia, and incubated in the laboratory under different conditions. No spoilage was observed in 130 samples incubated in open containers at 5 or 30 degrees C for up to 60 days. Spoilage occurred in 42 of 130 samples incubated in covered containers at 5 degrees C after about 80 days and was caused mainly by Penicillium spp. and Cladosporium spp. Mixed populations of lactic acid bacteria, yeasts, and molds were mostly responsible for spoilage in about 10 to 14 days of the 130 samples incubated in covered containers at 30 degrees C. The dominant spoilage organisms under these conditions were Lactobacillus delbrueckii subsp. delbrueckii, Lactobacillus fructivorans, Lactobacillus collinoides, Lactobacillus salivarius, Zygosaccharomyces mellis or Zygosaccharomyces rouxii, Candida sphaerica, Candida rugosa, Candida colliculosa, Candida pelliculosa, Candida famata, Pichia anomala, Aspergillus niger, and Penicillium spp. Although some variations among date cultivars in susceptibility to microbial spoilage were observed, moisture content and storage temperature were the most critical factors affecting spoilage.