A Novel Approach to the Study of Bread Porous Structure: Phase-contrast X-Ray Microtomography

ABSTRACT: The evaluation of bread quality can be carried out by performing a nondestructive investigation of its microstructure, which in turn can be performed by adapting image analysis techniques that enables one to obtain rapid, objective, and quantitative information. A suitable and reliable experimental methodology to investigate the porous structure of bread by means of the numerical image processing, and without any sample preparation, has been presented in this work. Different types of breads having varying degrees of porosity were studied by X-ray computerized phase-sensitive microtomography for the acquisition of digital high-resolution images. After acquisition, suitable numeric algorithms were applied to slice reconstruction. Finally, 3D images were rendered and analyzed.     

MICROWAVE BLANCHING OF CUBED POTATOES

Cubed potatoes cv. Primura were blanched by microwaves in water, NaCl solution, CaCl₂ solution and NaCl-CaCl₂ solution at selected powers and times. Mass and water gain/loss, firmness, starch gelatinization, color and polyphenoloxidase activity were evaluated. The results showed that all the blanching treatments induced a weight loss even if it was caused by a combined loss of water and dry matter in potatoes blanched in the saline solutions whereas it was a balance between water gain and dry matter loss in potatoes blanched in water. Firmness was affected in a negative way especially by the treatment time. Potatoes blanched in NaCl-CaCl₂ showed the highest firmness retention, whereas potatoes blanched in NaCl were less consistent. Treatment time and microwave power contributed in the same way to the starch gelatinization. It was necessary to prolong the time of treatment to 3–5 min and apply high power to inactivate polyphenoloxidase.     

MICROWAVE BLANCHING OF SLICED POTATOES DIPPED IN SALINE SOLUTIONS TO PREVENT ENZYMATIC BROWNING

Response surface methodology was applied to investigate the way in which variables such as time of treatment, sodium or calcium chloride concentrations and lactic acid concentration affect the microwave blanching of potato slices dipped in these solutions. Two three factor-five-level, second order central composite designs were developed to analyze the considered variables. Results showed that, with reference to polyphenoloxidase inactivation, the blanching in calcium chloride-lactic acid solution was more effective than the blanching in sodium chloride-lactic acid solution. Color measurements showed that, in the applied operative conditions, the best results were obtained by short blanching in sodium chloride-lactic acid solution at high lactic acid concentration and low NaCl concentration and by short blanching in calcium chloride-lactic acid at low lactic acid concentration or low calcium chloride concentration.     

CHANGES IN FREE FATTY ACID AND DIACYLGLYCEROL COMPOUNDS IN SHORT-RIPENING DRY-CURED SAUSAGE

A study on lipolysis of Southern Italy short-ripened dry-cured sausages manufactured without and with starters was carried out. Samples were submitted to microbiological and chemical analysis during drying and ripening, whereas sensory analysis was performed at the end of the ripening. The starters, addition caused the inhibition of the Enterobacteriaceae. An increase of free fatty acids (FFAs) and diacylglycerols (DAGs) during the ripening was observed. The addition of starter did not affect FFA and DAG release. The DAG profile including 1,2- and 1,3-isomers was analyzed for the first time in dry-cured sausages. Oleic, linoleic and palmitic acids, and 1,2-, 1,3-palmitinolein, 1,2- and 1,3-diolein were the most abundant compounds in FFA and DAG, respectively. A decrease in the concentration of some 1,2-DAG and an increase of 1,3-OO and 1,3-OP species during the process was observed. Finally, the addition of starter cultures slightly influenced the sensory properties of sausages.

PRACTICAL APPLICATIONS

In this work the development and application of an analytical method for the determination of free fatty acids (FFAs) and diacylglycerols (DAGs) in sausages was achieved. DAGs are intermediate products of hydrolysis and also constitute a substrate for hydrolysis reactions leading to FFA release. These latter compounds undergo a series of reactions leading to the formation of low-molecular-weight products responsible for sensory properties of dry-cured sausages. Therefore, the assessment of these lipolysis products is a useful tool for evaluating the ripening process of dry-cured sausages.     

AUTOXIDATION OF PACKED ROASTED ALMONDS AS AFFECTED BY TWO PACKAGING FILMS

Peeled and unpeeled almonds of Romana and Pizzuta varieties of almonds were roasted and packed under vacuum conditions, using two films having different barrier effects against O₂. The almonds were stored for eight months at room temperature in the dark and, at regular intervals, were analyzed to study the progress in lipid oxidation. Results showed that almond oxidation strongly depended on packaging: the film with the highest barrier effect against O₂ was able to better preserve almonds. With reference to Romana almonds, peeled almonds were slightly more oxidized than unpeeled almonds especially in the last phase of the storage. In the case of Pizzuta almonds, the difference between peeled and unpeeled nuts was more evident. The results of chemical and instrumental analyses were confirmed by the judgements of the panel test, pointing out a more positive evaluation for the Romana variety of almonds.