Fungal Population of Nutmeg (Myristica fragrans) Kernels Affected by Water Activity During Storage

The aim of this investigation was to determine the effect of various water activities (a w) on fungal population in nutmeg kernels during storage. The seed nutmegs were obtained from ripe fruits one week after they fell on the ground in North Minahasa Regency, North Sulawesi Province, Indonesia. The kernels (moisture content ± 10%) were stored 0, 15, and 30 days in various a w (0.75, 0.80, 0.83, 0.90, 0.97) using saturated salt solutions at 29 °C in sorption containers. Serial dilution method followed by a pour-plate method in Dichloran 18% Glycerol Agar (DG18) was used to isolate and quantify the fungal population. Results revealed that kernels stored at a w = 0.75 was not significantly ( p < 0.05) different from at a w = 0.80-0.83. Fungal population of kernels determined a w and significantly ( p < 0.05) influenced by duration of storage. Range of a w 0.80-0.83 has a smaller total fungal population than a w ≥ 0.90. Thirteen different genera/species were isolated and identified including Aspergillus and Eurotium (6 species), Penicillium (3 species), Fusarium (2 species), 1 species each of Cladosporium or Syncephalastrum, and isolate A. The largest total fungal population (5.0×10 5 CFU g -1) was present at the beginning of storage (a w = 0.97) and it was dominated by Penicillium citrinum (2.6×10 5 CFU g -1) followed by Cladosporium cladosporioides (1.7×10 5 CFU g -1). After 30 days of storage (a w = 0.97) the population of P. citrinum was still dominant with a population of 2.4×10 4 CFU g -1. Eurotium chevalieri followed with a population of 1.2×10 4 CFU g -1