1. Effect of osmotic dehydration as a pre-fermentation treatment on the quality and sensory characteristics of green table olives F. Kalomiri1, M. Alexandraki2, F. Karamitsiou2, A. Ntzimani1, E. Gogou1, V. Oikonomopoulou1, M. Krokida1, P. Taoukis1 1National Technical University of Athens, School of Chemical Engineering, Greece, 2Konstantopoulos S.A.-"OLymp", Katerini, Greece
Introduction
Results & Discussion
Water loss and solid gain in olives increased with increasing time of osmosis; an overnight osmosis resulted in water activity decrease from to (Fig. 1). Osmotic pre-treatment of olives was found to favor fermentation as lactic acid bacteria were the of olives was not very intense, due to their thick skin. dominant microbial population. In addition, at the end of osmotic dehydration, total solid gain was gr/100gr.
During the shelf life test selected quality indicators were monitored to evaluate the effect of the osmotic pre-treatment on the overall quality of the final products compared to green table olives that were conventionally produced without the osmotic pre-treatment. Selected quality indicators were microbial growth, texture, color, sensory evaluation (including sensory perception of salt) and sodium content. The measured evolution of the selected quality indicators confirmed the absence of pathogens while growth rates of spoilage indicated a shelf life of approximately 2 years.
Sodium content of green olives that were osmoticaly pre-treated prior to fermentation was 1200 mg/100g while sodium content was 1500 mg/100g in the conventional green table olives.
Osmotic pre-treatment of green olives can lead to the development of table-olives with superior nutritional and sensory characteristics while lowering the salt intake during fermentation.
Changes in lifestyle are in direct connection to dietary habits and determine consumer demand for novel foods. While previous years the trend was related to low-calorie products, nowadays there is a shift to alternative food products that ensure better health benefits. Years of research have shown that the Mediterranean type of diet is a very healthy one as it is considered to protect against heart attacks, cancer, obesity, etc. and is characterized by low fat consumption and high consumption of legumes, fruits and vegetables. Olives and olive based products are considered to be among the most prominent products in the Mediterranean diet.
Figure 1: Water activity decrease of olives as a function of treatment time during the osmosis treatment of olives with osmotic solution of glucose-syrop.
Table olives production involves a fermentation process using high concentration salt brines. On the other hand regulatory authorities have recommended reducing dietary intake of salt. The objective of this study was to explore the limitation of salt intake during olives fermentation by applying an osmotic dehydration pre-treatment and evaluate the effect of osmotic dehydration on the overall quality and shelf life of the final product.
Materials & Methods
Α 70% w/w glucose-syrup was used as osmotic solution for green table-olives prior to fermentation. Osmotic dehydration was monitored for water activity, water loss and solid gain in olives. All treatments were performed in pilot scale in industrial process line as depicted in Picture 1.
Figure 2: The effect of osmotic pre-treatment on texture, as expressed from the firmness of the final olive products.
Figure 3: Sodium content of conventional and osmotic pre-treated green table olives.
Picture 1. Osmotic dehydration pre-treatment in pilot scale as a pre-fermentation treatment of
green table olives.
The osmotic dehydration treatment was performed overnight for approximately 14 hours. During osmotic dehydration olives and osmotic solution samples were samples at predetermined time intervals and total solid gain (SG), water activity (aw) and water content were determined. Water activity was measured with the AquaLab 4TEV, Decagondevices, (USA).
Olives were then fermented for 3 months (7-8% NaCl brine) followed by pasteurization and packaging in low-salt solutions (3% NaCl). The shelf life, quality and sensory characteristics of the final products were monitored at 3 storage temperatures; 25, 35 and 45°C.
The measured evolution of overall sensory quality, salt perception, phenolic content and microbial growth during storage test confirmed the absence of pathogens while growth rates of spoilage indicated a shelf life of approximately 2 years. Salt content of final product was 12% lower than the conventional table olives.
Conclusions
Salt content of final products decreased by 20 % for osmotic dehydration compared to the conventional ones. Samples that were subjected to osmotic dehydration were sensory acceptable and presented a sweet, pleasant aftertaste. The study shows the efficacy of mild dehydration pre-treatments for the production of lower salt products that are characterized by superior sensorial characteristics.
References
Albarracín, W., Sánchez, I.C., Grau, R., Barat, J.M., 2011, “Salt in food processing; usage and reduction: A review”, International Journal of Food Science and Technology, 46(7), 1329–1336.
Cherubini C., Migliorini M., Mugelli M., Viti P., Berti A., Cinid E., Zanoni B., 2009, “Towards a technological ripening index for olive oil fruits”. Journal of the Science of Food and Agriculture, 89(4),
Escudero-Gilete, M.L., Melendez-Martinez, A.J., Heredia F. J., Vicario I.M., 2009, “Optimization of olive-fruit paste production using a methodological proposal based on a sensory and objective color analysis”. Grasas y Aceites, 60(4),
Taormina, P.J., 2010, “Implications of salt and sodium reduction on microbial food safety”. Critical Reviews in Food Science and Nutrition,
Acknowledgements
The project is funded by the O.P. Competitiveness and Entrepreneurship (EPAN ΙΙ), ROP Macedonia - Thrace, ROP Crete and Aegean Islands, ROP Thessaly - Mainland Greece - Epirus, ROP Attica, Greece