Some Functional and Utilization Characteristics of Sesame Flour and Proteins

Sesame defatted flour was prepared from dehulled seeds and the proteins extracted by isoelectric precipitation from an alkaline suspension of the flour. Temperature and pH effects on viscosity of a protein dispersion were measured using a Brookfield viscometer. Emulsifying capacity and emulsion stability were measured in mayonnaise and meat-type emulsions, respectively. Sesame flour was texturized by a simple method to produce a ground meat-like product with a hydration capacity of 380–440%. Sensory evaluation of meat loaves with 0–40% meat replaced by hydrated textured defatted sesame flour indicated no significant difference between samples. Viscosity of sesame protein dispersions at 90°C increased with increasing pH. The proteins did not form a self-supporting gel. Their emulsifying capacity proved to be relatively high when compared with traditional proteins.     

HEAT TRANSFER TO WATER AND SOME HIGHLY VISCOUS FOOD SYSTEMS IN A WATER-COOLED SCRAPED SURFACE HEAT EXCHANGER

Heat transfer in a water-cooled scraped surface heat exchanger has been investigated. The overall heat transfer coefficient in the heat exchanger is composed of three elements: heat transfer coefficient in the coolant jacket, resistance to heat flow in the separation wall and heat transfer coefficient inside the scraped cylinder. A method for assessing the heat transfer coefficient at the coolant side was developed. In contrast with studies published elsewhere, heat transfer was investigated with food systems which are non-newtonian and possess a complicated and unknown flowing behavior at higher shear rates. For water and three starch-based food products (starch content 12–18%) the heat transfer coefficients inside the scraped cylinder were measured for shaft speeds ranging from 1.67 to 10 revolutions/s. The experimental results were compared with heat transfer coefficients calculated with a model based on the penetration theory. For the starch-based products, in general, no consistent interactions between mass flow rates and internal heat transfer coefficients were observed. In the shaft speed range studied heat transfer coefficients at scraped surface varied from 3200 to 7800 W/m² K for water, from 500 to 3150 W/m² K for velouté sauce, from 670 to 1330 W/m² K for roux and from 780 to 1900 W/m² K for ragout.     

Evaluation of Gelation and Solubility of Bovine Plasma Protein Isolates

Gelation and solubility of bovine plasma protein isolates prepared from liquid plasma using different acids (HCl, H₃PO₄, H₂SO₄) and bases (NaOH, Na₂CO₃) were evaluated and compared to commercial plasma. Protein recovery was over 90%. Solubility at 1% (w/v) was low in pH range 4.0 to 5.5 but similar to commerical plasma in pp range 5.5 to 8.0 (p < 0.01). All isolates gelled at a concentration o 6.0%. Only isolate H₃PO₄-Na₂CO₃ and commercial plasma gelled at a minimum concentration of 4.0%. This concentration decreased to 2.4% for the same isolate when 0.025M Ca⁺⁺ ion was added.     

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.     

Potentially probiotic açaí yogurt

The aim of this work was to evaluate the suitability of yogurt containing açaí pulp as a food carrier of probiotic cultures. Probiotic yogurts containing increasing amounts of açaí pulp (3, 5 and 7%) were processed and submitted to a physicochemical analysis and viable microbial count during refrigerated storage. In general, all the physicochemical parameters showed variations proportional to the amount of açaí pulp in the product formulation. Probiotic activity was verified throughout refrigerated storage for all the products, although there was a fall of one logarithmic cycle for both micro-organisms during this period (10⁷–10⁸ CFU/mL).     

Combined Stress Effects on Growth of Zygosaccharomyces rouxii from an Intermediate Moisture Papaya Product

Stress factors studied included 0.95 a_w adjusted with sucrose and glycerol, pH (4.0, 3.5, and 3.0), potassium sorbate (0, 500, 1000, and 1500 ppm) and sodium bisulfite (0, 100, and 150 ppm). These were tested on a strain of Zygosaccharomyces rouxii isolated from an intermediate moisture (IM) papaya product. Z rouxii was very sensitive to SO₂. A combination of 100 ppm SO₂, 500 ppm sorbate and pH 4.0 is recommended to prevent spoilage of IM fruits by Z. rouxii. The minimum a_w for growth in sucrose-glycerol broth was between 0.62 and 0.64 in the absence of antimicrobials and in the range of optimal pH for this yeast.     

Rheological Properties of Renneted Reconstituted Milk Gels by Piezoelectric Viscoprocess: Effects of Temperature and Calcium Phosphate

Scanning electron microscopy (SEM) and rheology and permeability were used to evaluate effects of clotting temperature and calcium phosphate on reneted reconstituted milk gels, especially microstructure and permeability. Dynamic measurements with a piezoelectric Viscoprocess determined rheological properties of curd after various times of renneting. An increase in clotting temperature accelerated specific rennet action and gel formation; maximum stiffness was reached faster but its value was weaker. Addition of calcium phosphate increased rate of gel formation. Maximum stiffness was reached faster but its value was not changed. Gel microstructure was not very different but its permeability coefficient decreased.     

EFFECTS OF ORGANIC ACIDS, NISIN, LYZOZYME AND EDTA ON THE SURVIVAL OF YERSINIA ENTEROCOLITICA POPULATION IN INOCULATED ORANGE BEVERAGES

Inactivation of a Yersinia enterocolitica strain by 3.4% ascorbic acid (AA), 0.5% citric acid (CA), 0.2% lactic acid, 100 IU/mL nisin, 2,400 IU/mL lysozyme and 20 mM ethylenediaminetetraacetic acid disodium salt (EDTA ), alone and combined, was studied at different temperatures (4 and 25C) in commercial and laboratory-prepared orange beverages. In laboratory-prepared juice, highest reductions (between 3.06 and 4.07 log units) were obtained with acid mixtures at 25C after 20 min of incubation. At 24 h of incubation, EDTA was bactericidal and the mixtures with nisin or lysozyme resulted in count reductions of 6.03 and 5.98 log units, respectively. In commercial orange beverage, AA and CA gave reductions of 5.43 and 4.26 log units, respectively. The three acid mixtures were bactericidal within the first 10 min. EDTA alone or mixed completely inhibited Y. enterocolitica strain at 6 and 24 h of incubation. At 4C, all the results were significantly lower than at 25C.

PRACTICAL APPLICATIONS

Yersinia enterocolitica is a common cause of gastrointestinal disorders and may lead to sequelae. This pathogen can maintain its virulence in a wide temperature range and under adverse conditions such as pH lower than 4. There are reports describing the isolation of Y. enterocolitica from water and ice in Brazil and Latin America. The sale of unpasteurized drinks is a common practice in our region and their consumption has increased over the past years. In the present work, chemical compounds and biological inhibitors were studied. Some of these compounds showed to be efficient for reducing Y. enterocolitica populations. Furthermore, they did not modify the organoleptic characteristics of the beverages and they are not toxic for human beings.     

ANTIBIOTIC RESISTANCE OF CAMPYLOLOBACTER ISOLATED FROM AUTOMATED BROILER FARMS

The use of the same antibiotics in animal food and conventional medicine can cause problems in the treatment of human diseases, because poultry frequently carry human pathogens. The aim of the present study was to determine the antibiotic resistances patterns of Campylobacter jejuni isolated from the rearing environment of broiler chickens – litter, drinking water, feed and the bird's cloaca. The results showed significant resistance to the following antibiotics: sulfonamide (77%), tetracycline (100%), erythromycin (80%) and penicillin G (100%). Intermediary resistance was present in bacitracin (90%), trimethoprim (100%), vancomycin (100%), chloramphenicol (97%), nalidixic acid (100%) and azithromycin (100%). However, new studies need to be carried out in Brazil to determine the resistance amplitude of this microorganism in other animals and humans. It is important to define some control strategies of the antibiotics used in animal production and human medicine.