Greek dry-salted olives: Monitoring the dry-salting process and subsequent physico-chemical and microbiological profile during storage under different packing conditions at 4 and 20 °C |
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Authors: | Efstathios Z. Panagou |
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Affiliation: | National Agricultural Research Foundation, Institute of Technology of Agricultural Products, 1 Sof. Venizelou, Lycovrissi GR-141 23, Greece |
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Abstract: | Naturally black olives cv. Thassos were processed in dry salt according to industrial procedure by uniformly dispersing 40 kg of coarse salt in 100 kg freshly harvested olives. Dry-salting process was monitored by measuring selected physico-chemical (weight loss, NaCl content, pH, aw, reducing sugars) and microbiological parameters (total viable counts, lactic acid bacteria, enterobacteria, yeasts, pseudomonads). Total weight loss amounted to 21 g/100 g after 80 days of dry-salting. Salt content in the fruits increased to 7.4 g/100 g followed by a decrease in water activity from 0.98 to 0.76. The pH did not change significantly presenting a slight decrease from 5.25 to 4.92. The initial microflora of the fruits comprised of lactic acid bacteria (4.1 log10 cfu/g), yeasts (5.7 log10 cfu/g), enterobacteria (3.7 log10 cfu/g ) and pseudomonads (4.0 log10 cfu/g). In the end of dry-salting, no microbial groups were enumerated apart from yeasts, due to the low water activity of the product. After dry-salting, olives were packed in HDPE bags under air (control samples) and 100 ml/100 ml CO2. Another lot of fruits was dipped in 1 g/100 ml solution of potassium sorbate for 10 min prior to packing in the same bags under aerobic conditions. All packages were stored at 4 and 20 °C for a period of 180 days. During storage, the microbial flora comprised of yeasts, while no lactic acid bacteria, enterobacteria, pseudomonads or Staphylococcus aureus were detected as the low water activity/high salt content does not favour their growth. At 4 °C, the population of yeasts declined steadily throughout storage, but to a different extend depending on the packing treatment. At 20 °C, only potassium sorbate was effective in suppressing yeast growth. All packing treatments prevented fungal growth at both storage temperatures, apart from the samples stored in air. The pH, aw and salt content did not change significantly throughout storage. |
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Keywords: | Dry-salting process Dry-salted olives Modified atmosphere packaging Naturally black olives Packaging Potassium sorbate |
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