Reduction of trimethylamine oxide by <i>Shewanella</i> spp. under modified atmospheres in vitro

Two strains of Shewanella spp. were isolated from cod fillets packed in modified atmosphere (60% CO2, 30% O2, 10% N2). One of the strains was identified asShewanella putrefaciens. The other strain could not be fully identified but was determined as a Shewanella spp. different from S. putrefaciens. The effect of modified atmosphere (CO2, O2) on the growth of the two strains and on the reduction of TMAO to TMA was studied using solid medium from fish extract packed under variable mixtures of CO2, O2 and N2. All the samples were incubated at 7°C for 7 days. The Shewanella-like strain was shown to be a stronger TMAO reducer and was more resistant to CO2 than S. putrefaciens per se. Modified atmosphere packaging of marine fish can inhibit the growth and TMAO-reducing activity of S. putrefaciens when 50% of CO2 together with 10% of O2 are introduced into the packaging atmosphere. The growth and TMAO-reducing activity of the Shewanella-like strain can be inhibited when higher proportions of CO2 together with as high as possible proportions of O2 are introduced into the packaging atmosphere. It is suggested that a combination of 60-70% CO2 and 30-40% O2 is introduced into the packaging atmosphere in order to prevent TMA production by Shewanella spp

Effect of modified atmosphere packaging on the TVB/TMA-producing microflora of cod fillets

Cod fillets (Gadus morhua) were packed under modified atmospheres, with four different gas compositions (60% CO2-10% O2-30% N2, 60% CO2-20% O2-20% N2, 60% CO2-30% O2-10% N2, 60% CO2-40% O2), and stored at 6 degrees C. Plate counts were carried out after 3, 4, 5, 6 and 7 days, to follow the growth of aerobic and anaerobic bacteria, lactic acid bacteria, H2S-producing bacteria and Enterobacteriaceae. The production of total volatile bases (TVB) and trimethylamine (TMA), and the changes in pH of the fillets were measured. Modified atmosphere packaging (MAP) had in general an inhibitory effect on the growth of the microflora but limited inhibition of the production of TVB and TMA. Despite the fact that increased oxygen proportions in the atmosphere contributed in a slightly lower production of TMA, all the samples had a TVB and TMA content high enough to be considered as spoiled after 4 days' storage at 6 degrees C. A total aerobic plate count at 25 degrees C of a 10(6) cfu/g, combined with the presence of only a 10(3) cfu/g of H2S-producing bacteria, which are normally considered as TMAO-reducing organisms in fish, cannot explain the strong increase in TMA. A high cell concentration of more than 10(8) cfu/g of Shewanella putrefaciens is required for production of a TMA level normally found in spoiled fish. This suggests that there could be another type of bacterium in fish, not involved in the spoilage of unpacked fish, which is resistant to 60% CO2, is not H2S-producing, and shows a high TMAO-reducing capacity. This bacterium could be Photobacterium phosphoreum

Effect of processing on phenolic composition of olive oil products and olive mill by-products and possibilities for enhancement of sustainable processes

The bio-functional properties of olive oil products and by-products rely greatly on the proportions and types of the endogenous phenolics that may favorably/unfavorably change during various processing conditions. The olive oil industrial activities typically produce (i) olive oils, the main/marketable products, and (ii) olive mill by-products. The mechanical processing of olive oil extraction is making progress in some areas. However, the challenges inherent in the existing system, taking into consideration, the susceptibilities of phenolics and their biosynthetic variations during processing, hamper efforts to ascertain an ideal approach. The proposed innovative means, such as inclusion of emerging technologies in extraction system, show potential for sustainable development of olive oil processing. Another crucial factor, together with the technological advancements of olive oil extraction, is the valorization of olive mill by-products that are presently underused while having great potential for extended/high-value applications. A sustainable re-utilization of these valuable by-products helps contribute to (i) food and nutrition security and (ii) economic and environmental sustainability. This review discusses typical processing factors responsible for the fate of endogenous phenolics in olive oil products/by-products and provides an overview of the possibilities for the sustainable processing to (i) produce phenolic-rich olive oil and (ii) optimally valorize the by-products.info:eu-repo/semantics/publishedVersio

Influence of partial replacement of olive oil on frying performance of palm olein

The influence of partial replacement of palm olein (POo) with olive oil (Oo), (25 and 50%, w/w) was investigated during five consecutive days of frying. The results indicated that frying performance of POo was significantly (P < 0.05) influenced by partial replacement with olive oil. The highest change in peroxide value (PV), anisidine value (AV), totox value (TV), total polar compound (TPC), viscosity and melting point was shown by the control sample; whereas the replacement of 50% (w/w) palm olein with 50% (w/w) olive oil exhibited the least changes in PV, AV, TV, TPC, viscosity and melting point during the frying process. This study suggests that the partial replacement of palm olein containing a high proportion of saturated fatty acids (i.e., palmitic acid) with olive oil containing a high content of monounsaturated fatty acid (i.e., oleic acid) can provide oil blends with higher chemical stability against oxidation. On the other hand, the prepared oil blend remained liquid at ambient temperature, thereby enhancing the physical stability induced by partial replacement with olive oil