Microbiological quality and biophenol content of hot air‐dried Thassos cv. table olives upon storage

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Microbiological quality and biophenol content evolution was studied in minimally processed Thassos cv table olives by hot air dehydration under mild conditions (40°C, 24 h, aw = 0.893) and storage under characteristic packaging conditions (vacuum, 100% N2 and air) at 4 and 20°C over a period of 180 days. No salt was used in the production line or packaging. The undesirable microorganisms (Enterobacteriaceae, Staphylococcus aureus, Bacillus, Clostridium) were undetectable until the end of the storage period. Also, modified atmospheres prevented fungal growth at both temperatures apart from the samples stored in air, in which Penicillium and Aspergillus spp. were identified. At 20°C, a coexistence of mesophilic bacteria and yeasts occurred. At 4°C, yeasts were the predominant microflora. All of the samples analysed were found to be rich sources of the bioactive ingredients, elenolic acid (EA) glycoside and EA. Hydroxytyrosol and derivatives, caffeic acid, luteolin 7-O-glycoside, apigenin derivative and p-coumaric acid derivative assigned as comselogoside were the prevailing phenols in all of the samples. Although the levels of the above compounds decreased upon processing and storage, especially in the samples stored at 4°C, their presence is important for stability because of their high antimicrobial and antioxidant activities. Practical applications: Reducing the amount of salt used in the table olive processing and preservation seems to be an important innovation though this is not a straightforward process, as salt plays an important role in the microbiological quality of the end product. Our study faces such a challenge in the case of minimally processed Thassos cv olives by hot air dehydration under mild conditions (40°C, 24 h, aw = 0.893), which, traditionally, are processed by means of salt. To our knowledge, this is the first report focusing on the evolution of microbiological quality and biophenol content of hot air-dried Thassos olives upon storage under characteristic modified-atmosphere packaging conditions (vacuum and 100% N2). This experimentation provided evidence that this product can be considered as one with a satisfactory microbiological quality and nutritional value with regard to bioactive ingredients and the absence of salt. Assessment of the ‘best before date’ of this product is needed before commercialization.