Effects of Different Filtration and Clarification Techniques on Palestinian Virgin Olive Oil Chemical and Microbial Quality
Virgin olive oil filtration is a pre-treatment usually used before bottling to facilitate suspended particle removal and reduce the moisture content so that the quality and organoleptic properties are preserved during storage. In the current study, samples of virgin olive oils were subjected to different clarification and filtration techniques such as (1) commercial filtration (CF) using diatomaceous earth as a filter aid, (2) clarification by insufflating of carbon dioxide, and (3) argon gas. All treated samples as well as control unfiltered (UF) virgin olive oil (VOO) were bottled under dark conditions in diffused daylight glass bottles and kept at room temperature for six months. Basic quality indices (free acidity (FA), peroxide value (PV), and extension coefficient) and total polar phenol were determined within respected time of analysis during the storage period of six months. In addition, microbial quality was evaluated by determination of yeasts and molds, total plate count, Bacillus cereus, and clostridium perfringens. The main results showed that at the end of the storage, acidity increased in all samples with time in both storage conditions, whereas samples stored in dark more stable compared to those stored under diffused daylight. On the other hand, clarified samples with CO2 showed significant stability compared to the rest of the samples stored under diffused day light. Peroxide values (PV) and K232 increased in all stored samples. Moreover, K270 increased with time, and showed more stability in samples stored in dark. Total polar phenols decrease in all samples, but showed no significant difference among all samples after 180 days of storage. Microbial results revealed the presence of yeasts and molds in all samples at the beginning of storage, and then disappeared after 135 days for all samples except UF. Total plate count, Bacillus cereus, and clostridium perfringens were not found in any stored VOO.