IMPROVING FATTY EXTRUDATE STRUCTURE WITH AMYLASE AND PROTEASE

The extrusion of fatty flour at temperatures less than 100C on the one hand favors less leakage of oil from plant and products, but on the other hand reduces the degree of expansion unless suitable technological coadjuvants are used. Enzymes are generally used in the preparation of bread to mellow gluten and to soften texture. At the moment, there is little information about the use of enzymes to improve the texture of extruded products. The effect of two commercially available enzymes (GRINDAMYL Amylase 1000 and GRINDAMYL Protease 41) on the texture of products obtained from wheat and almond flours extruded at low temperature (54C) was studied. GRINDAMYL Protease 41 was found to affect the rheological characteristics of dough by rapid decreasing the consistency during farinographic analyses and by improving the structure of extrudates with a high lipid content (reduced breaking strength, high% porosity and high water solubility index).     

MODELING OF PREHEAT TREATMENT OPTIMIZATION APPLIED TO FRESH‐CUT “ROCHA” PEAR

ABSTRACT

Response surface methodology based on a five‐level, three‐variable central composite rotatable design was used for modeling the effects of preheat treatments on fresh‐cut “Rocha” pear quality. Studied variables were time (t: 0–150 min), temperature (T: 20–50C) and posttreatment storage time (St: 0–20 days, 5C). The quality‐affecting parameters including color, firmness, pH, soluble solid content, and total ascorbic acid content were the monitored dependent variables. Results provide reasonable estimation of the impact of preheat treatments on the quality of fresh‐cut “Rocha” pear and its shelf life. The time–temperature range of 33–41C during less than 20 min was selected as the conditions that best provided surface browning control, without impairing other studied quality parameters, with an estimated 8‐day shelf life period. The achieved kinetic changes of polyphenoloxidase, partial reduction in enzyme activity (ca. 23%) and depletion of phenolic content (ca. 11%) could be responsible for the browning control.

PRACTICAL APPLICATIONS

Minimal processing, namely cutting operations, triggers physiological reactions which limit fresh‐cut Rocha pear shelf life. Superficial browning is one of the major concerns to this industry, and new “clean” methodologies aiming at the inhibition of such reaction and maximization of the product shelf life will benefit not only from product marketability but also will respond to the consumers' demand of “chemical free” products. Heat treatments have been used to improve fresh‐cut commodities' browning resistance. The present work evaluated the use of preheat treatments against this physiological disorder during storage. Results will provide an optimized preheat treatment that grants high‐quality fresh‐cut Rocha pear with suitable shelf life.

     

CHEMICAL CHARACTERIZATION AND PREPARATION OF SALTED MINCES FROM BIGEYE GRUNT AND LONGFIN BONEFISH

The proximate chemical composition, amino add and fatty add profile of bigeye grunt (Brachydeuterus auritus) and longfin bonefish (Pterothrissus belloci) minces were determined. Both minces contained a low fat content. Polyunsatu‐rated fatty adds represented more than 50% of the fatty adds in bigeye grunt but in the case of longfin bonefish the percentages of saturated, mono‐, and polyunsaturated were similar. The amino add profile of minces from these species was very similar. The preparation of salted minces using different drying methods is described. The chemical and physical characteristics of raw and dried salted minces as well as cooked products were measured. Dried salted minces from these species had high water uptake and cooked products presented a low salt content (1 %). Cooked rehydrated salted minces from longfin bonefish were lighter in color than those from bigeye grunt and color values were not significantly influenced by the salt level used in the preparation.     

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.     

MINORITY POLITICAL REPRESENTATION AND LOCAL ECONOMIC DEVELOPMENT POLICY

ABSTRACT: This article examines the relationship between black and Hispanic political representation in local government and the economic development policy approaches pursued by city administrations. It asks whether the administrations of black and Hispanic mayors are more likely than other administrations to follow policy approaches that address the interests of minority residents. In each aspect of development policy examined, the results indicate that administrations of minority mayors are no more likely than other administrations to promote the interests of minority constituents.     

Behaviour of Listeria monocytogenes inoculated into Minas Frescal cheese made by direct acidification or lactic culture during refrigerated storage

The behaviour of Listeria monocytogenes Scott A artificially inoculated into Brazilian Minas Frescal cheese manufactured with the addition of a lactic culture or by direct acidification with lactic acid was evaluated at 5 and 10°C for 25 days. In cheese produced with a lactic culture, the counts remained almost unchanged during storage, whereas cheeses produced by direct acidification presented an increase in the counts of 2–3 log cycles. The profiles of the lactic bacterial counts, associated with those of L. monocytogenes, show a strong influence of the competitive starter culture on the survival of L. monocytogenes . This suggests that the addition of starter culture is an efficient way to control the growth of L. monocytogenes in these products.     

THERMAL INACTIVATION KENETICS of PECTINESTERASE EXTRACTED FROM ORANGES

A study was carried out on the kinetics of thermal inactivation of pectines terase (PE), extracted from the pulp of Valencia and Navel oranges. Moreover, the influence of intrinsic factors on the kinetics of Navel orange PE was investigated. In a citric acid buffer, at a pH of 3.7 and 4.2, the enzyme was more thermostable as compared to water. However, at pH 3.2 an increased inactivation and an increased temperature sensitivity of the rate constant was observed. Ca²⁺-ions also enhanced the inactivation, whereas the temperature sensitivity of the rate constant decreased. In presence of sucrose, a diminished inactivation of PE was observed, and addition of sucrose only slightly influenced the activation energy.     

STUDY ON INTERACTION AMONG EXTRUSION-COOKING PROCESS VARIABLES AND ENZYME ACTIVITY: EVALUATION OF EXTRUDATE STRUCTURE

A blend of wheat flour (moisture content 11.61%) and different amounts of two commercial enzymes like GRINDAMYL (GA) amylase 1000 (0–0.1 g/kg) and GA protease 41 (0–1.0 g/kg) were extruded through a co-rotating twin-screw extruder.
The effects of barrel temperature (60–120C), dough moisture (20–36%), screw speed (100–400 rpm) and different amounts of enzymes on structure of extrudates (porosity and break strength) were studied using response surface methodology.
Results showed that the highest value of porosity (62.47%  ±  4.07) was obtained at the highest value of barrel temperature (120C) and at the largest amounts of GA protease 41 (1.0 g/kg) or GA amylase 1000 (0.1 g/kg). However, the simultaneous addition of large amounts of both enzymes caused a negative effect on expansion degree (porosity  <  30%). Large amounts of moisture dough and GA amylase 1000 resulted in a high value of break strength (25.7 N/mm²) and in stiff-textured extrudates .

PRACTICAL APPLICATIONS

This research could provide some information about the effects of and the interactions between extrusion parameters and enzyme activities, which are commonly used to produce bakery products, in order to improve the texture of extrudates processed at low barrel temperatures, i.e., 60C, for example, extrudates with thermolabile components like vitamins or extrudates with high lipid fraction like breakfast cereals, pet food, etc.