Ana Blandino

Cereal-based fermented foods and beverages

Cereal grains constitute a major source of dietary nutrients all over the world. Although cereals are deficient in some basic components (e.g. essential aminoacids), fermentation may be the most simple and economical way of improving their nutritional value, sensory properties, and functional qualities. This review focuses first on some of the indigenous fermented foods and beverages produced world-wide that have not received the scientific attention they deserve in the last decades. Products produced from different cereal substrates (sometimes mixed with other pulses) fermented by lactic acid bacteria, yeast and/or fungi are included. Finally, newly developed cereal-based foods with enhanced health properties will also be reviewed.

Formation of calcium alginate gel capsules: influence of sodium alginate and CaCl2 concentration on gelation kinetics.

The formation kinetics of calcium alginate gel capsules is studied. An increase in the concentration of alginate gives rise to a reduction in membrane thickness, while an increase in the concentration of calcium chloride leads to the formation of a thicker film. Experimental data are adjusted to the binomial diffusion equation.

Immobilization of glucose oxidase within calcium alginate gel capsules

Abstract Glucose oxidase (GOD) was encapsulated within calcium alginate gel capsules. The effects of gelation conditions on capsule characteristics such as thickness, percentage of enzyme leakage and encapsulation efficiency were studied and the optimal conditions for GOD encapsulation obtained. Oxidation of glucose to gluconic acid followed Michaelis–Menten kinetics.

Glucose oxidase release from calcium alginate gel capsules

Diffusion of glucose oxidase within calcium alginate gel capsules has been assayed and the experimental data fitted to a simple semi-empirical power equation, which is used to analyse the solute release from polymeric devices. It was found that an increase in the concentration of sodium alginate and calcium chloride gives rise to a reduction in the enzyme leakage. This was verified when glucose oxidase (GOD) diffusion percentages were compared in capsules with thicknesses of the same order of magnitude but obtained under different experimental conditions. So, the use of sodium alginate and calcium chloride solutions of concentrations 0.5% w/v and 2.6% w/v, respectively, lead to a diffusion percentage of 25 +/- 2. This percentage was reduced to 8 +/- 3 when sodium alginate and calcium chloride concentrations were fixed at 1% w/v and 4% w/v, respectively, even though the thicknesses of the capsules were of the same order of magnitude.

Utilisation of whole wheat flour for the production of extracellular pectinases by some fungal strains

The possibility of producing pectinases by Rhizopus stolonifer and Aspergillus awamori, using cereal raw materials as substrate, was investigated. The whole wheat flour acted as a good nutrient source for the cultivation of the microorganisms and exo- and endo-polygalacturonases (PG) were produced in submerged culture. In this respect, it was possible to obtain polygalacturonase activities at an acceptable yield, in comparison with a typical defined medium described in the literature for pectinase production. The synthesis of both enzymes occurred in both strains in the absence of pectin, demonstrating the constitutive nature of these enzymes; nevertheless, production was increased by the addition of a small amount of pectin to the flour.

Evaluation of microwave-assisted pretreatment of lignocellulosic biomass immersed in alkaline glycerol for fermentable sugars production

A pretreatment with microwave irradiation was applied to enhance enzyme hydrolysis of corn straw and rice husk immersed in water, aqueous glycerol or alkaline glycerol. Native and pretreated solids underwent enzyme hydrolysis using the extract obtained from the fermentation of Myceliophthora heterothallica, comparing its efficiency with that of the commercial cellulose cocktail Celluclast®. The highest saccharification yields, for both corn straw and rice husk, were attained when biomass was pretreated in alkaline glycerol, method that has not been previously reported in literature. Moreover, FTIR, TG and SEM analysis revealed a more significant modification in the structure of corn straw subjected to this pretreatment. Highest global yields were attained with the crude enzyme extract, which might be the result of its content in a great variety of hydrolytic enzymes, as revealed zymogram analysis. Moreover, its hydrolysis efficiency can be improved by its supplementation with commercial β-glucosidase.

Xylanase production by Aspergillus awamori under solid state fermentation conditions on tomato pomace

Inthiswork,� tomatopomace,� awasteabundantlyava ilableintheMediterraneanandothertemperate� climatesagrofoodindustries,�hasbeenusedasraw �materialfortheproductionofsomehydrolyticenz ymes,� includingxylanase,�exopolygalacturonase�(exoPG), �cellulase�(CMCase)�and�α�amylase.�Theprincipalst ep� oftheprocessisthesolidstatefermentation�(SSF )�ofthisresiduebyAspergillus awamori.�Inseveral� laboratoryexperiments,�maximumxylanaseandexoPG �activitiesweremeasuredduringthefirstdaysof�

Calcium alginate gel as encapsulation matrix for coimmobilized enzyme systems.

Encapsulation within calcium alginate gel capsules was used to produce acoimmobilized enzyme system. Glucose oxidase (GOD) and catalase (CAT) were chosen as model enzymes. The same values of Vmax and Kmapp for the GOD encapsulated system and for the GOD-CAT coencapsulated system were calculated. When gel beads and capsules were compared, the same catalyst deactivation sequence for the two enzymes was observed. However, when capsules were employed as immobilization support, GOD efficiencies were higher than for the gel beads. These results were explained in terms of the structure of the capsules.

Comparative study of alcohol dehydrogenase activity in flor yeast extracts

The highest activities of alcohol dehydrogenase were obtained when flor yeasts were grown on L-lactic acid as the main carbon source. The strains with the lowest average of alcohol dehydrogenase activities, grown on glucose and ethanol, make up the velum on wines during the early stages ageing. One of the strains studied ( Saccharomyces cerevisiae, M10) may be a suitable source from which to isolate this enzyme (32 units of activity per mg protein).

Modelling and simulation of a bienzymatic reaction system co-immobilised within hydrogel-membrane liquid-core capsules

Abstract A mathematical model applicable to the analysis and simulation of a heterogeneous bienzymatic reaction system is presented. The glucose oxidase–catalase (GOD–CAT) system co-encapsulated within hydrogel-membrane liquid-core capsules was chosen as the model system in this study. The proposed model considers a non-uniform biocatalyst concentration profile within the support and the deactivation phenomena of the two enzymes. Simulation experiments allowed us to elucidate the distribution of the two enzymes within the capsules. It seemed that GOD was distributed across the whole of the particle while CAT was confined almost exclusively to the core of the capsule. From the simulated glucose and hydrogen peroxide concentrations within the capsules, it was deduced that the hydrogen peroxide formed in the glucose oxidation reaction led firstly to the deactivation of the catalase and, after this point, GOD deactivation was accelerated.