Isothermal gelation behavior of myofibrillar proteins from white and red chicken meat at different temperatures.

This paper provides insights in the isothermal gelation behavior of white and red chicken myofibrillar proteins (CMP) at different temperatures (20 to 80°C) and the underlying aggregation mechanism, allowing understanding of structure formation in poultry products during thermal processing. At low temperatures (20 to 60°C), an increase in aromatic surface hydrophobicity (SoANS) was found, suggesting potential formation of hydrophobic interactions between CMP. At higher temperatures (60 to 80°C), high SoANS and a significant decrease in total sulfhydryl amount (SH-amount) strongly indicate the presence of hydrophobic interactions and disulfide bonding, resulting in aggregation, as suggested by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The elastic modulus G' after 60 min isothermal heating (G'60min) significantly increased at 70 or 80°C, depending on the type of CMP. Differences in G'60min between white and red CMP were rather small at low temperatures (20 to 60°C). However, at 70°C, white CMP reached higher G'60min compared to red CMP, while the opposite was observed at 80°C. Overall, for every temperature studied, SoANS and SH-amount of red CMP were higher compared to white CMP. The differences in G'60min, SoANS, and SH-amount between white and red CMP were probably due to different isoforms. The results may help to steer quality characteristics of poultry products through intelligent choice of processing conditions.

Coupled cultivation and pre-harvesting of microalgae in a membrane photobioreactor (MPBR).

A new and effective concept is proposed for microalgae cultivation and pre-harvesting using a membrane photobioreactor (MPBR), in which the bioreactor is coupled to membrane filtration by cultivating Chlorella vulgaris. A basic simulation was first performed to understand the behavior of the hybrid system. The effectiveness of the MPBR for cultivation and pre-harvesting was proven. The membrane completely retained the biomass, which then was partly recycled into the bioreactor to maintain a high biomass concentration, thus enhancing flexibility and robustness of the system. The MPBR can operate at both higher dilution and higher growth rates, resulting in a 9× higher biomass productivity. In addition, pre-harvesting can be achieved by applying variable concentration factors in the filtration stage. The membrane permeate was recycled to the reactor as feed medium without affecting the algae growth, which offers a substantial reduction of 77% in the water footprint.

Harvesting microalgal biomass using a magnetically induced membrane vibration (MMV) system: filtration performance and energy consumption.

This study was performed to investigate the effectiveness of submerged microfiltration to harvest both a marine diatom Phaeodactylum tricornutum and a Chlorella vulgaris in a recently developed magnetically induced membrane vibrating (MMV) system. We assess the filtration performance by conducting the improved flux step method (IFM), fed-batch concentration filtrations and membrane fouling autopsy using two lab-made membranes with different porosity. The full-scale energy consumption was also estimated. Overall results suggest that the MMV offers a good fouling control and the process was proven to be economically attractive. By combining the membrane filtration (15× concentration) with centrifugation to reach a final concentration of 25% w/v, the energy consumption to harvest P. tricornutum and C. vulgaris was, respectively, as low as 0.84 and 0.77kWh/m(3), corresponding to 1.46 and 1.39 kWh/kg of the harvested biomass.

Role of transparent exopolymeric particles in membrane fouling: Chlorella vulgaris broth filtration.

Recent reports show strong evidence for the involvement of transparent exopolymer particles (TEPs), mainly produced by microalgae in natural environments, in membrane fouling in a wide range of membrane filtration processes. The objective of this study is to fundamentally investigate the direct role of TEPs on membrane fouling by using different Chlorella vulgaris broth solutions and different fractions of such broth (the soluble and bound fractions, the cells separated from these fractions and the cells with their bound sugars, separated from the soluble fraction) as filtration feed. The relation between the feed properties and their filterability over three membranes was determined. Scanning electron microscopy and light microscopy showed that the foulant types differed for each broth fraction and confirmed the role of TEPs in the fouling of microfiltration membranes. In addition, this study contributes to the role of TEPs in the filtration of microalgae cultivated for commercial reasons.

Harvesting microalgal biomass using submerged microfiltration membranes.

This study was performed to investigate the applicability of submerged microfiltration as a first step of up-concentration for harvesting both a freshwater green algae species Chlorella vulgaris and a marine diatom Phaeodactylum tricornutum using three lab-made membranes with different porosity. The filtration performance was assessed by conducting the improved flux step method (IFM) and batch up-concentration filtrations. The fouling autopsy of the membranes was performed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR). The cost analysis was estimated based on the data of a related full-scale submerged membrane bioreactor (MBR). Overall results suggest that submerged microfiltration for algal harvesting is economically feasible. The IFM results indicate a low degree of fouling, comparable to the one obtained for a submerged MBR. By combining the submerged microfiltration with centrifugation to reach a final concentration of 22% w/v, the energy consumption to dewater C. vulgaris and P. tricornutum is 0.84 kW h/m(3) and 0.91 kW h/m(3), respectively.

Role of yeast proliferation in the quality degradation of strawberries during refrigerated storage.

Quality changes of strawberries during storage can be caused both by microbiological and physiological processes. There is little known about the possible contribution of microbiological processes to the quality degradation of strawberries. In this study, quality of strawberries during storage was evaluated by analytical and sensorial analyses. It was the aim to investigate the influence of microbiological activity on the changes of different quality factors of strawberries during storage. During storage at 7 degrees C, quality was mainly determined by the odor and by visual defects. Regarding the odor, highly microbiologically contaminated late-season strawberries packaged in air at 7 degrees C became sensorially unacceptable due to the presence of high amounts of ethyl acetate. This could be attributed to the yeast proliferation: at yeast concentrations above 5.0 log cfu/g, an increase in ethanol was detected in the headspace of the strawberries. It was shown that ethanol was converted to ethyl acetate by strawberries resulting in an unacceptable odor. In an experiment with low microbiologically contaminated early-season strawberries, not reaching the above mentioned yeast counts, less ethyl acetate was detected which resulted in strawberries that were sensorially acceptable during the whole storage period (12 days). Strawberries packaged in modified atmosphere conditions showed a different quality pattern due to the effect of decreased O2-concentrations on both microbiological and physiological processes. This paper demonstrates that also microbiological processes on strawberries should be considered as they could play an important role in the sensorial quality when interacting with physiological processes.