KINETICS OF BIOETHANOL PRODUCTION FROM WHEAT MILLING BY-PRODUCTS

An overview of the potential application of wheat milling by‐products as substrate for bioethanol production is presented. In order to select a suitable microorganism, model fermentations were conducted using glucose and dry baker's yeast. The overall ethanol yield was nearly stable (ca. 0.35 g/g), independent of mash glucose concentration; mashes with 100 g glucose/L resulted in an overall ethanol productivity of 3.48 g/L·h. Slurries containing low‐grade wheat flour (LG) (100, 200 or 300 g/L) were used for simultaneous saccharification and fermentation (SSF) with Zymomonas mobilis. Fermentation performance was evaluated based on ethanol concentration (P), productivity (Q_v), yield (Y_P/S), production rate (Q_p) and glucose consumption rate (Q_s). Mashes containing 200 g LG/L produced about 52 g ethanol/L, with Q_vof 2.17 g/L·h. Based on the relatively high fermentation rate of LG, reaching peak ethanol productivity within ca. 9 h of SSF, considerable savings on fermentation time was achieved. Using Z. mobilis for LG fermentation, P was about 30% higher than that obtained with Saccharomyces cerevisiae.     

NUCLEOTIDE CATABOLISM IN COLD STORED ADDUCTOR MUSCLE OF SCALLOP (ZYGOCHLAMYS PATAGONICA)

The postmortem catabolism of adenosine triphosphate (ATP) in cold stored scallop adductor muscles was examined. The change In the pH of stored muscles was also investigated. The ATP content increased for a short time after death and afterwards decreased up to 24 h of storage. Thereafter, the nucleotide level remained unchanged up to 120 h of storage. The ADP content slightly decreased up to 48 h and after that remained unchanged. The AMP slowly accumulated to around 15% of the total nucleotide concentration when the ATP decreased. Small amounts of IMP were detected in all samples. Conversely, adenosine (Ado) was not detected. Inosine (HxR) slightly increased after 48 h of storage and hypoxanthine (Hx.) significantly increased after 24 h. The 260/250‐absorbance ratio of muscle extracts and the pH of stored muscles fell sharply up to 24 h and then decreased slowly. The Hx contents were positively correlated (P < 0.01) with both the Hx/AMP ratios and the K values.     

MOISTURE ADSORPTION BEHAVIOR OF BISCUITS FORMULATED USING WHEAT, OATMEAL AND PASSION FRUIT FLOUR

Moisture adsorption isotherms from a new biscuit considered as functional food were determined using a gravimetric static method at 25 and 40C and over a range of relative humidity from 0.112 to 0.903. The biscuit had 2.5, 3.3, 10.0 and 31.0% of ash, fiber, protein and fat, respectively, and 4.7% moisture content. The equilibrium moisture content of the biscuit (kg/kg) increased when the storage temperature at any given water activity ( A _w) was reduced. The experimental data were analyzed using different models, namely Guggenheim–Anderson–de Boer (GAB) (three-parameter relationships), Henderson and Oswin (both models with two parameters), which exhibited a sigmoid shape at the studied temperatures. The maximum isosteric heat of sorption was 21.6 kJ/mol, which exponentially decreased when the moisture content was increased. The GAB model was found to be the most suitable for describing the adsorption characteristics at the temperature and A _w range studied, according to the relative error and the coefficient determination.

PRACTICAL APPLICATIONS

This article describes the characterization of moisture adsorption behavior of a new biscuit considered as functional food. In general, the sorption behaviors of several foods have been studied extensively; nevertheless, a reduced number of published articles about biscuit sorption isotherms are found in the literature. The experimental data reported in this article may be important for the scientific community of the food science and technology. Isosteric heat of sorption is important for the determination of the binding strength of water to the food, as well as the amount of water present in the food.     

Gelling Properties of Actomyosin from Pre- and Post-Spawning Hake (Merluccius hubbsi)

The biochemical properties and the characteristics of heat-induced gelation of natural actomyosin (NAM) from pre- and post-spawning hake were studied. Mg²⁺ ATPase activity, reduced viscosity and myosin/actin mole ratio of NAM from post-spawning fish were higher than those of pre-spawning ones. Gelation of both actomyosin at 10 mg mL^?1 of protein concentration was optimal at 60°C and pH 6.0. The highest rigidity was reached at 0.40M and 0.44M KCl with NAM from pre and post-spawning hake, respectively. Irrespective of heating temperature, ionic strength conditions and at pH range 5.5–7.5, rigidity of post-spawning hake NAM gels was higher than those of pre-spawning fish. Scanning electron micrographs of pre- and post-spawning hake NAM showed “actin-type” and “myosin-type” ultrastructures, respectively.     

Thermal Denaturation in Fish Muscle Proteins During Gelling: Effect of Spawning Condition

We studied thermal denaturation of myofibrillar proteins from pre-and post-spawning hake by differential scanning calorimetry (DSC), and evaluated denaturation kinetics under both conditions. The denaturation enthalpies of all pre-spawning fish muscle extracts were less than those from post-spawning. The area under the DSC thermogram corresponding to myosin denaturation was smaller in myofibrillar extracts from pre-spawning than from post-spawning hake, while the areas corresponding to denaturation of actin were similar. Between 40 and 55°C the myosin denaturation rates were greater for post-spawning than for pre-spawning hake. Both entalphies and kinetic data indicated proteins of fish in a better biological condition (post-spawned) denature more rapidly and completely.     

The observation of large magnetite (Fe3O4) crystals from magnetotactic bacteria by electron and atomic force microscopy

Magnetite crystals inside coccoid magnetotactic bacteria found in lagoons near Rio de Janeiro city were examined by electron microscopy (EM) and atomic force microscopy (AFM). For AFM, ultrathin sections of bacteria embedded in Epon resin were etched with an ethanolic NaOH solution and observed both in the height and in the force modes. Comparative electron microscope images were useful for identifying crystalline reliefs in the etched sections. Different situations representing particular arrangements of crystal chains were observed by AFM. The majority of the bacteria examined presented unusually large magnetite crystals which remained strongly attached in linear chains even after the laboratory procedures for their isolation. This behaviour is different from all other biogenic magnetite crystals isolated so far. It is suggested that this attachment is due to the strong field between individual crystals as well as to the contact areas, which are the largest observed until now. The correct identification of a particular topography by AFM as a crystal relief may be critical when crystals are not aligned in chains; in these cases the linear dimensions and the presence of well-defined edges and faces are important features to be taken into account. Characterization of the crystal faces is important for the study of magnetotactic micro-organisms since the crystalline habits seem to be species-specific. Observation of etched sections proved to be a helpful approach for crystal relief observation, especially when small amounts of bacteria were available.     

AUTOLYSIS OF PROTEINS FROM PRESPAWNED HAKE (MERLUCCIUS HUBBSI MARINI) DURING IN VITRO STORAGE OF MYOFIBRILS AT 20 AND 37C

The in vitro autolysis of hake myofibrillar proteins was investigated. No evidence of proteolysis was observed in myofibrils after 44 h of incubation either in presence or in absence of protease inhibitors at 20C. A 180‐kDa component present at zero time in the SDS‐PAGE gels of myofibrils from prespawning hake was degraded after 44 h of incubation at 37C. Degradation of the 180‐kDa component was accompanied by an increase in low molecular weight and TCA soluble peptides. These changes were not observed in myofibrils incubated in the presence of protease inhibitors (1 mM PMSF+ 1 mM iodoacetic acid + 1 mM of EDTA). Both PMSF and EDTA used alone partially inhibited the degradation of myofibrillar proteins. This inhibition was lower than that produced in the presence of both inhibitors, Azocaseinolytic activity was almost exclusively associated with the 180 kDa‐component eluted from SDS‐PAGE gels. These results suggest that both metallo and serine proteinases could be involved in the autolysis of myofibrils at 37C.     

CAUSAL FUNCTIONAL REPRESENTATION LANGUAGE WITH BEHAVIOR-BASED SEMANTICS

Understanding the design of a device requires both knowledge of the general physical principles that determine its behavior and knowledge of its intended functions. However, the majority of work in model-based reasoning has focused on using either one of these types of knowledge alone. In order to use both types of knowledge in understanding a device design, one must represent the functional knowledge in such a way that it has a clear interpretation in terms of observed behavior. We propose a new formalism, causal functional representation language (CFRL),for representing device functions with well-defined semantics in terms of behavior. CFRL allows the specification of conditions that a behavior must satisfy, such as occurrence of temporal sequences of events and causal relations among them and the components. We have used CFRL as the basis for afunctional verification program, which determines whether a behavior achieves an intended function.     

ABSENCE OF PROTEOLYSIS IN PURIFIED MYOFIBRILS OF POSTSPAWNED HAKE (MERLUCCIUS HUBBSI MARINI) DURING IN VITRO STORAGE AT 37C

The biochemical behavior of myofibrils from postspawned hake during in vitro storage at 37C was investigated. SDS‐PAGE, densitometric analysis of the band areas corresponding to the major myofibrillar proteins, and TCA soluble peptides determination showed no evidence of proteolysis in myofibrils after 44 h of incubation either in presence or in absence of a cocktail of protease inhibitors (1 mMPMSF+1mMiodoacetic acid + 1mM of EDTA). The absence of proteolysis in stored postspawned hake myofibrils contrasts with the autolysis in those from prespawned fish previously reported, indicating an influence of the reproductive cycle on the proteolytic activity closely associated to myofibrils.     

CHANGES IN PROTEIN COMPOSITION DURING STRAWBERRY (Fragaria × ananassa Duch.) FRUIT RIPENING1

The changes in strawberry native proteins and polypeptides during ripening were studied. Analysis of protein extracts by nondenaturing electrophoresis showed the presence of a protein species only in the ‘25% Red’ and later ripening stage. This 40 kD polypeptide was hardly detected in ‘Large green’ and ‘White’ fruit extracts. The polypeptide profile, obtained with SDS-PAGE, also changed during ripening. While most polypeptides were found in all ripening stages, the distribution of some of them varied during ripening. Protein synthesis (measured by ³⁵ S-methionine labelling) in strawberry was mainly directed towards the regeneration of previously existing proteins. As ripening proceeded, the synthesis of 67 and 63 kD polypeptides increased, while those of 82, 56 and 25 kD decreased. Three very-abundant polypeptides (36, 24 and 23 kD) were located in the achenes and were not labelled in any ripening stage.