Changes in proteins during Teruel dry-cured ham processing

The aim of this work was to investigate the degradation of the water-soluble and myofibrillar proteins during the production of "PDO Teruel" cured ham using SDS-PAGE, and measurement of proteolytic activities (cathepsins B+L, cathepsin L, cathepsin D), as factors that influence the sensory characteristics of this product. This paper contributes to the specific characterisation of a product included in the European Union list of special quality products. The results showed that water-soluble proteins decrease considerably due to salting out and drainage after salting. The degradation of myofibrillar proteins is more pronounced during the ripening process, particularly in the last four months when the main proteins responsible for the structure of muscular tissue are affected. There is an important residual enzymatic activity for cathepsin B, L and D, which must be a decisive factor in the proteolysis observed during "PDO Teruel" ham processing.     

Effect of storage on biochemical and microbiological parameters of edible truffle species

The effects of different storage treatments on the most common edible truffle species, such as Tuber magnatum and Tuber borchii (white truffles), Tuber melanosporum and Tuber aestivum (black truffles), were analysed. Biochemical and microbiological profiles were monitored, in order to evaluate possible alterations during truffle preservation. After harvesting, some fresh samples were kept at 4 °C for 30 days, other samples were frozen at −20 °C for one month, thawed and preserved at 4 °C; the remainder were autoclaved.     

MICROBIAL ENZYMES AND THEIR EFFECTS ON EXTRACT RECOVERIES FROM UNMALTED ADJUNCTS

Radial diffusion tests were used to detect β-glucan-, starch-, protein-, pentosan- and triglyceride-degrading enzyme activities in a variety of commercial enzyme preparations. Some implications of the presence of unexpected enzymes in particular preparations are discussed. A series of laboratory mashes were made with grists of milled barley, extruded barley, and extruded wheat, using various enzyme additions and temperature-time programmes. In addition a limited number of experiments were made with pale ale barley malt, and wheat flour pellets. Extract yields varied from acceptable to outstandingly good. The most intensive mashing system, with enzyme supplementation, increased the extract yield of an all-malt mash by 3·9% relative to the control mashing programme. Some worts were evaluated for Total Soluble Nitrogen (T.S.N.), Free Amino Nitrogen (F.A.N.) and viscosity. Slow wort-filtration rates occurred in some mashes although the viscosities of the worts from these mashes were low. This problem did not occur in any of the samples intensively mashed over a 5 h period. The results apparently exclude the possibility that a simple, reliable technique for estimating the extract yields of adjuncts could be devised, using these enzyme preparations.     

Biological Kinetic Data Evaluation of an Activated Sludge System Coupled with an Ultrafiltration Membrane

A membrane bioreactor (MBR) system treating wastewater containing high molecular weight compounds was operated at solids retention times (SRTs) ranging from 30 to 2 days. Chemical oxygen demand removal efficiencies exceeded 99% and effective nitrification was obtained at SRTs between 30 and 5 days. A significant shift in the biological population structure was observed at the 2 days SRT as the content of gram-negative microorganisms increased and nitrifying bacteria were washed out. At this low SRT, limitations in the biological reaction kinetics resulted in incomplete degradation of the feed protein increasing the presence of soluble organic matter in the effluent. Furthermore, the diluted mixed liquor prevented the formation of a filtration cake on the membrane surface, further deteriorating effluent quality. Biological kinetic data parameters were analyzed using three different representations for biomass: volatile suspended solids, lipid phosphates, and total enzymatic activity. All three indicators exhibited similar trends resulting in very comparable estimates for endogenous decay coefficients, thus demonstrating the reliability of volatile suspended solids as a measure for biological activity in activated sludge. Lower than typical endogenous decay rates in the MBR suggested favorable environmental conditions for respiration and a lower potential for self oxidation and predation. The true yield coefficient was in the range of conventional activated sludge systems, refuting previous suggestions of lower yields in MBRs.     

Comparison of Enzyme Activities in Vegetated and Nonvegetated Sediments

This study focuses on the effect of aquatic plants on the changes of enzyme activities in wetland sediments. Wetland plants play essential roles both as a carbon supplier for microbes which synthesize enzymes and as a regulator for enzyme activity by modifying hydrochemistry in the rhizosphere. Although numerous studies have been carried out on soil enzymes, little information is available on the vertical distribution and temporal variation of enzyme activities affected by the presence of plants in wetlands. Our results clearly show that sediments with wetland plants exhibit significantly higher enzyme activities of β-glucosidase, arylsulfatase, phosphatase, and N-acetylglucosaminidase (P<0.05) up to a depth of 15?cm throughout the year, whereas only lower values were observed even at the surface of sediments (0–3?cm) without plants. However, in the field, there were no statistically significant changes of enzyme activities associated with the changes of season and the vertical position along the depth (P<0.05). This indicates that the organic carbon supplemented by root exudates, root debris, and plant residue played an important role in increasing enzyme activities in the sediments with plants. The mechanisms driven by aquatic plants such as oxygen diffusion and transpiration-induced advection did not induce the short-term changes in enzyme activities. Exceptionally, the changes of sulfate availability and the increase of temperature have implications in the changes of arylsulfatase activities depending on the location (vegetated versus nonvegetated sediment) (P = 0.000), season (growing season versus senescence) (P = 0.042), and sediment depth (P = 0.002). Since wetlands treat wastewaters with variable carbon sources, it would be beneficial to maintain increased enzyme activities in the regeneration of inorganic nutrients from organic materials. In addition, the presence of plants would vertically extend the area where the higher enzyme activities are observed and the movement of wastewater takes place and, consequently, could accelerate wetland treatment efficiency.     

Asymmetric Reduction of (R)-Carvone through a Thermostable and Organic-Solvent-Tolerant Ene-Reductase

Ene-reductases allow regio- and stereoselective reduction of activated C=C double bonds at the expense of nicotinamide adenine dinucleotide cofactors [NAD(P)H]. Biological NAD(P)H can be replaced by synthetic mimics to facilitate enzyme screening and process optimization. The ene-reductase FOYE-1, originating from an acidophilic iron oxidizer, has been described as a promising candidate and is now being explored for applied biocatalysis. Biological and synthetic nicotinamide cofactors were evaluated to fuel FOYE-1 to produce valuable compounds. A maximum activity of (319.7±3.2) U mg⁻¹ with NADPH or of (206.7±3.4) U mg⁻¹ with 1-benzyl-1,4-dihydronicotinamide (BNAH) for the reduction of N-methylmaleimide was observed at 30 °C. Notably, BNAH was found to be a promising reductant but exhibits poor solubility in water. Different organic solvents were therefore assayed: FOYE-1 showed excellent performance in most systems with up to 20 vol% solvent and at temperatures up to 40 °C. Purification and application strategies were evaluated on a small scale to optimize the process. Finally, a 200 mL biotransformation of 750 mg (R)-carvone afforded 495 mg of (2R,5R)-dihydrocarvone (>95 % ee), demonstrating the simplicity of handling and application of FOYE-1.     

Enzyme Activity and Nutritional Quality of Peach (Prunus persica) Juice: Effect of High Hydrostatic Pressure

The inactivation of polyphenol oxidase and pectin methylesterase in peach juice was investigated after high hydrostatic pressure processing at 400–600 MPa and 25°C for 5–25 min, respectively. At 400 MPa, polyphenol oxidase and pectin methylesterase were activated by 7.3 and 2.6%. At 500 and 600 MPa, polyphenol oxidase and pectin methylesterase were inactivated significantly with increasing the pressure and time, and the inactivation kinetics was fitted by the first order model. Moreover, some physio-chemical properties were studied. The results revealed that high hydrostatic pressure treatment preserved more L-ascorbic acid and maintained the color and sensory quality better than thermal treatment.     

The hepatopancreas enzymes of the crustaceans Munida and their potential application in cheese biotechnology

Proteolytic and peptidase activities were extracted from the hepatopancreas of the crustaceans Munida and characterized by enzymatic assay, 2D zymography and mass spectrometry. Results showed the presence of several isotrypsin-like and isochymotrypsin-like enzymes, aminopeptidases and carboxypeptidases A and B. Six different acidic forms of trypsin were detected using specific inhibitors and 2D zymography. Trypsin-like activity was higher than chymotrypsin-like activity. On the basis of previous evidences in food biotechnology and cheese production, the digestive enzymes of the crustaceans Munida were tested for their ability to degrade casein, a process involved in cheese production. As a result, the Munida enzymes were found to degrade the chymosin-derived β-casein fragment f193-209, one of the peptides associated with bitterness in cheese, revealing their possible application in cheese technology to lower the unpleasant bitter flavour in some cheeses.