Combined effect of an O2 absorber and oregano essential oil on shelf-life extension of Greek cod roe paste (tarama salad) stored at 4 °C

In the present study the combined effect of an O-2 absorber and oregano essential oil (0.1% v/w) on shelf life extension of Greek cod roe paste (tarama salad) stored under refrigeration (4 degrees C) was investigated. The study was based on microbiological [Total viable count (TVC), Lactic Acid Bacteria (LAB), Enterobacteriaceae, H2S-producing, yeast and molds and Clostridium spp.), physicochemical (pH, fatty acid composition, thiobarbituric acid (TBA), and color) and sensory (color, odor, and taste) changes occurring in the product as a function of treatment and storage time. Aerobically packaged tarama salad stored at 4 degrees C was taken as the control sample. Results showed that TVC exceeded 7 log cfu/g on day 12-13 of storage for control samples and day 31-32 for samples containing oregano oil. Samples containing either the O-2 absorber or the O-2 absorber plus oregano oil never reached 7 log cfu/g during the 60 day storage period. LAB were only partially inhibited by the oregano oil and/or the O-2 absorber. Yeasts and molds were totally inhibited by the O-2 absorber. Enterobacteriaceae populations were below the method detection limit (2 log cfu/g) H2S-producing bacteria were the dominant spoilage microorganisms. Clostridum spp. was absent in 25 g sample. pH decreased from an initial value of 4.36 to 3.03 depending on specific treatment. Color parameters L* and b* increased and a* decreased in control samples as well as in samples containing oregano oil. Color parameters remained unaffected in samples containing the O-2 absorber. TBA expressed as malondialdehyde (MDA) values increased from 1.5 mg/kg to 3.4, 3.2 and 2.9 mg/kg for samples containing oregano oil, the O-2 absorber and O-2 absorber plus oregano oil at the point of sensory rejection, respectively. Saturated fatty acids (SFA) increased during storage with a respective decrease in monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) both in control samples and samples containing oregano oil. Fatty acid composition remained unaffected in all samples containing the O-2 absorber. Sensory shelf life was 24 days for the control samples, 32 days for samples containing oregano oil, 60 days for samples containing the O-2 absorber and at least 60 days for samples containing the O-2 absorber plus oregano oil. Industrial relevance: Oxygen absorbers as well as plant essential oils are considered natural means of preservation and may substantially extend the shelf life of foodstuffs while maintaining desirable sensory attributes (taste,odor and color). (C) 2009 Elsevier Ltd. All rights reserved.