Enzymes are used in baking to improve dough handling properties and the quality of baked products. Glucose oxidase (GO) is an enzyme with oxidazing effect due to the hydrogen peroxide released from its catalytic reaction. In this study, the macroscopic effect of increasing glucose oxidase concentrations on wheat dough rheology, fresh bread characteristics and its shelf life during storage was determined. A reinforcement or strengthening of wheat dough and an improvement of bread quality can be obtained with the addition of GO, although inverse effects were obtained when excessive enzyme levels were added. The analysis of the gluten proteins at molecular level by high performance capillary electrophoresis and at supramolecular level by cryoscanning electron microscopy revealed that the GO treatment modified gluten proteins (gliadins and glutenins) through the formation of disulfide and nondisulfide crosslinks. The high molecular weight glutenin subunits showed to be the most susceptible glutenin fraction to the oxidation action of GO. Excessive addition of GO produced an excessive crosslinking in the gluten network, responsible of the negative effect on the breadmaking properties.

No abstract

No abstract

No abstract

Calcium plays a very important role in the maintenance of quality in vegetable foods and it is used as a texturing agent to preserve the structure of minimally processed vegetables. The osmotic dehydration (OD) of 'Granny Smith' apple parenchyma by immersion in a sucrose solution allows us to obtain products with sensorial characteristics similar to those of fresh products, but it produces a loss of cellular integrity. Here we study the use of calcium as a possible preservative for the microstructural integrity of the product during OD, as well as to test whether cellular permeabilization improves the impact of calcium on the edible parenchyma of the 'Granny Smith' apple. Sodium dodecyl sulfate (SDS) has been used for convenience as a permeating agent although we recognize this may not be used in practice. The microstructure of the OD apple treated with calcium chloride and with SDS has been compared with fresh apple by means of light microscopy, transmission electron microscopy and low temperature scanning electron microscopy. The results show that calcium has a protective effect on the structural integrity during OD: it strengthens the cellular walls cements, avoids cellular collapse and protects protoplasts from plasmolysis. Although SDS favours calcium penetration, its use is not advisable since it encourages the destructuring effect of the OD and counteracts the consolidating effect of calcium.