Combined effect of antimicrobial edible coatings with reduction of initial microbial load on the shelf-life of fresh hake (Merluccius merluccius) medallions

Two distinct strategies were combined to preserve fresh fish (Merluccius merluccius) under refrigeration at 4 °C for 12 days: (i) the application of an antimicrobial edible coating enriched with oregano essential oil (OEO) or carvacrol (CV) and (ii) the reduction of initial microbial load by good handling practise and the use of sodium hypochlorite (NaOCl). The action of antimicrobial coatings alone retarded the growth of Enterobacteriaceae, lactic acid bacteria (LAB) and H₂S producing bacteria on fish samples. The reduction of initial microbial load by itself only affected the evolution of LAB, but not the rest of the bacterial groups. When using both techniques combined, edible antimicrobial coatings were significantly more effective with additional and significant delays in the growth of mesophilic, psychrotrophic and Pseudomonas bacteria. Thus, the use of both strategies combined resulted in a reduction of the counts of all bacterial groups after 12 days of storage which ranged from 1.5 log and 8 log, in Pseudomonas and H₂S producing bacteria, respectively. Moreover, no significant differences were observed when comparing the microbiological evolution of samples treated with OEO compared to those only treated with CV.     

Microbial Diversity of Ground Beef Products in South Korean Retail Market Analyzed by PCR-DGGE and 454 Pyrosequencing

The purpose of this study was to assess the microbial community in ground beef purchased from local stores in the north central area of South Korea. A total of 31 ground beef samples showed 3.77 ± 5.16 × 10⁵ CFU/g on aerobic plate counts, and PCR-based denaturing gradient gel electrophoresis was performed to assess the microbial community, which revealed a diverse profile among the products. Four of these samples were selected for further analyses via 454 pyrosequencing. Pseudomonas was the most frequently identified genus in terms of relative abundance (4.54–73.8%), and other bacteria such as Lactobacillus, Acinetobacter, and Carnobacterium were also identified in the ground beef. The presence of bacteria can affect the spoilage of ground beef products depending on the microbial populations, and understanding these populations may help limit spoilage and/or foodborne illness. This study illustrates the microbial diversity occurring among Korean ground beef products, even within a local region, and provides a molecular approach for potential ground beef microbial quality assessment.     

Simultaneous nitrification and denitrification with electricity generation in dual‐cathode microbial fuel cells

BACKGROUND: Nitrogen removal using microbial fuel cells (MFCs) is of great interest owing to the potential benefits of bioenergy production. In this study, simultaneous nitrification and denitrification in dual‐cathode MFCs was investigated. RESULTS: The dual‐cathode MFCs investigated were capable of generating electricity and removing nitrogen, influenced by operating methods, nitrogen loading rates and external resistance. Depending on the ammonium concentration in the anode chamber, 84–97% of the ammonium nitrogen was removed via nitrification in the aerobic cathode. The removals of nitrate and total nitrogen were relatively low (～50%) at the influent ammonium concentration of 80 mg NH₄⁺‐N L^?1, but were significantly improved to more than 90% at a lower ammonium input (40 and 20 mg NH₄⁺‐N L^?1). When the electrode couples were electrically connected for different purposes, with high power output from the anode/aerobic cathode and high current generation from the anode/anoxic cathode, nitrogen removal was also improved. An investigation of aeration suggested that factors other than carbon supply, possibly inefficient reactor configuration, also limited the performance of the developed MFC. CONCLUSION: The experimental results demonstrated that the proposed pathway was feasible with effective nitrogen and organic removal. This study provided valuable information for the further development of a continuously operated dual‐cathode MFC system. Copyright © 2011 Society of Chemical Industry     

Evaluation of pH‐treated fish sarcoplasmic proteins on rheological properties of fish myofibrillar protein mediated by microbial transglutaminase

Fish sarcoplasmic protein (SP) could be exploited in the water‐holding agent for fish protein gels, except that the gel strength is reduced. The adjustment of pH could modify protein interactions to overcome the inferior effect. Fish SP solutions were adjusted to pH 3 or 12, neutralised to pH 7 and lyophilised to be pH‐treated SPs. These SPs along with lyophilised untreated SP (Normal SP) were incorporated into fish myofibrillar protein (MP) with microbial transglutaminase (MTG). The denaturation temperature (T_d) of MP mixed with normal SP was 66 °C with the lowest shear stress value. The denaturation of MP mixed with pH‐treated SP reduced to be 57 °C, resulting in increased shear stress. The cooking loss of MP gel was reduced by adding pH‐treated SPs, while the breaking forces were similar to control. The result indicated that pH‐treated SPs could be used to reduce cooking loss of MTG‐mediated MP gels without affecting the gelling properties.     

Antimicrobial Activity of Parabens in Submicron Emulsions Stabilized with Lecithin

Antimicrobial efficacy of methyl and propylparaben combination as potential preservatives for submicron emulsions, and the effect of oil and lecithin concentration on the microbial growth were investigated. Parabens were ineffective in standard or doubled concentrations as per pharmacopoeial criteria. Poor growth inhibition and multiplication of reference strains point to protective and growth properties of submicron emulsions. No correlation was observed between oil/lecithin ratio and efficacy of parabens; partitioning of the latter into the oily phase and lipophilic domains could be the reason for such effect. Further studies are necessary to establish a stable and safe composition of such formulations.     

Composition and Structure of the Bovine Milk Fat Globule Membrane—Some Nutritional and Technological Implications

Milk fat is dispersed in milk as small, spherical globules, stabilized in the form of emulsion by its surrounding membrane. This membrane, called the milk fat globule membrane (MFGM), is created in the secretory cells of the mammary gland, and represents an ordered and unique biophysical system. This review characterizes the main milk fat globule components, their structure, and intracellular origin. The milk fat globule membrane has many potentially bioactive components. These are discussed in terms of their health effects for the native and processed globules. Because of their functional and nutritional properties, MFGM components can be used as valuable ingredients in the manufacture of new functional foods.     

Mass balance and kinetic analysis of anaerobic microbial dechlorination of pentachlorophenol in a continuous flow column

A mass balance and kinetic investigation of anaerobic dechlorination of pentachlorophenol (PCP) was undertaken using an enriched microbial consortium in a laboratory scale continuous flow column, as a model microbial permeable reactive barrier. The chlorine balance showed that 50 µM PCP was largely dechlorinated to phenol with the formation of a small quantity of 3-chlorophenol as an intermediate metabolite (hydraulic retention time 7.6 days), and the chlorine removal efficiency reached 36 µM d^-1. When the initial PCP concentration was increased to 100 µM the chlorine removal efficiency increased 1.5 times. However, the dechlorination activity disappeared after 7.4 pore volumes (58 days), demonstrating the susceptibility of the dechlorination culture to high concentrations of PCP. Lactate released hydrogen as an electron donor during PCP dechlorination, with acetate, propionate, CO₂ and CH₄ as byproducts. The carbon balance showed that some of the organic carbon source (PCP, lactate) in the influent was converted to gas and utilized for biomass growth in addition to organic metabolites. The kinetic study was conducted in a batch culture and yielded 1.99 mg l^-1 biomass growth per unit of chlorine consumption (µM). The Monod equation was well fitted to the specific growth rate of 1.38 d^-1 and a half saturation constant of 0.29 µM. The organic chlorine removal rate in the batch culture was consistent with the results in the flow column, indicating the feasibility of and potential for in situ estimation and prediction through batch culture studies.     

Evaluation of various salt levels and different dairy proteins in combination with microbial transglutaminase on the quality characteristics of restructured pork ham

The objective of this study was to evaluate the quality characteristics of restructured pork hams (RH) manufactured with various salt levels (0.5%, 1.0%, and 1.5%) and different dairy proteins (sodium caseinate, SC and whey protein isolate, WPI; 1.0%) in combination with microbial transglutaminase (MTGase; 0.3%). Reduced‐salt (0.5% and 1.0%) RH resulted in reductions of moisture contents (%), textural springiness, cooking yield and most sensory preferences (P < 0.05). When dairy proteins in combination with MTGase were incorporated into the manufacture of RH, SC with MTGase was shown to reduce cooking loss (CL, %) and to increase the textural springiness and chewiness of RH, whereas WPI with MTGase increased textural springiness and chewiness, as well as the shear value of RH (P < 0.05). On the contrary, MTGase with dairy proteins improved the sensory preferences of reduced‐salt (1.0%) RH to give it similar sensory properties to those of the regular‐salt (1.5%) RH controls (CTL) (P > 0.05). The findings of this study demonstrated that the combination of 1.0% dairy proteins and 0.3% MTGase could affect improvements in the functional, textural and sensory properties of reduced‐salt (1.0%) RH.