Poultry Processing Line Speeds as Related to Bacteriologic Profile of Broiler Carcasses

Aerobic plate counts, Enterobacteriaceae, E. coli counts; and Salmonella prevalence were determined on broiler carcasses obtained in a comtnercial slaughter establishment in Puerto Rico. Samples were obtained from three sites in the production process. Each site represented an end-point of a discrete segment of the slaughter process. Whole bird carcass rinses (300) were randomly collected over 4 days of production for several linespeeds. Samples were collected for birds processed at 70 birds/min (BPM), 80 BPM, 90 BPM, and three replications of samples at 100 BPM (June 1990 to May 1991). A total of 1,800 carcass rinses were analyzed. Mean bacterial counts and Salmonella prevalence did not change significantly with processing line speeds.     

Temperature Mapping of Particles During Aseptic Processing with Magnetic Resonance Imaging

Magnetic Resonance Imaging (MRI) was used to obtain 2-dimensional temperature maps in potatoes undergoing aseptic processing. The change in precession frequency of protons served as the temperature indicator. The larger particles (6.9 and 3.84 cm3) showed a δT (T_surface - T_center) of up to 22±0.4°C 45s after exiting the heat exchanger with the δ (T_outlet - T_inlet) of the carrier fluid in the heat exchanger at 30 to 45°C. No AT was measured between the center and the surface of particles <2.05 cm³ pumped at <22.7 L/min. The average fluid to particle convective heat transfer coefficient (h_fp) for the heat exchanger and holding tube was calculated using a finite element method. The hfp was from 600 to 2500 and >3000 W/m²°C for the large (6.9 cm³ cubes) and smaller particles respectively.     

EFFECTS OF VARIETY AND GROWTH SEASON ON THE ORGANOLEPTIC AND NUTRITIONAL QUALITY OF HYDROPONICALLY GROWN TOMATO

The effects of variety and season on several organoleptic and nutritional quality parameters (i.e., dry weight (dw), total sugars, soluble solid compounds, titratable acidity (TA), electrical conductivity (EC), juiciness, firmness, vitamin C (vit C), total phenolic compounds, hydrophilic antioxidant capacity and minerals) of five different varieties of tomatoes (i.e., Jack, Cabrales, Jaguar, Iker and Nevada) grown in two crop cycles (spring and autumn) were studied. Each variety presented its own specific characteristics regarding the chosen parameters. Firmness, TA and EC were season dependent, whereas soluble solids content did not change between cycles. In some varieties, the dw, juiciness and total sugars were affected by climatic conditions. The total phenolic compounds and the hydrophilic antioxidant capacity were variety dependent in both cycles. By contrast, the vit C content was variety dependent only in the autumn cycle. Similarly, these latter parameters (phenolic compounds, hydrophilic antioxidant capacity and vit C) were also season dependent, showing higher values in the spring than in the autumn cycle. The effect of tomato variety and season on mineral contents is also discussed. Those tomatoes grown in the spring cycle had better quality according to the organoleptic parameters studied here as well as to a higher antioxidant capacity. The percentages of the recommended dietary allowances supplied by the studied tomatoes were not significantly affected by variety or season, despite differences in their physicochemical compositions.     

Occurrence of coagulase-positive Staphylococci, microbial indicators and physical–chemical characteristics of traditional semihard cheese produced in Brazil

Coagulase-positive Staphylococci and microbial indicators of the 'Requeijão do Norte', a traditional semihard cheese, were surveyed in Brazil. Coagulase-positive Staphylococci were found in quantities of up to 9.4 log cfu/g. The coagulase gene was detected in isolates physiologically classified as coagulase-negative. The SEB and TSST-1 toxins were detected. Salmonella spp. were not detected. High levels of total and fecal coliforms (≥ 210 MPN/g) and moulds (≥   6.48 log cfu/g) were found in most samples. The values of physical–chemical parameters and water activity showed the greatest variations. These results suggest a possible risk that this cheese may pose to consumers.     

HEAT SHOCK REDUCES BOTH CHILLING INJURY AND THE OVERPRODUCTION OF REACTIVE OXYGEN SPECIES IN YELLOW PITAYA (HYLOCEREUS MEGALANTHUS) FRUITS

ABSTRACT

Yellow pitaya fruits were heat‐shocked (25C/24 h), stored at 2C for 14 days and then held for 13 days at 18C. Chilling injury (CI), respiration rate, hydrogen peroxide (H₂O₂), superoxide anion radical (O₂•^‐) and lipid peroxidation product (LPP) levels were measured. Pitting and browning were detected in the control fruit when moving from 2 to 18C. Minor CI symptoms were found in the treated fruit. There was a rapid increase in the levels of H₂O₂, O₂•^‐ and LPP in the control fruits when moved to 18C. At the end of the storage, the levels of these compounds were 4.5‐, 4.9‐ and 6.2‐fold higher, respectively, in the control than in the treated fruit. The results suggest that the reactive oxygen species levels in the heat‐shocked fruit were adequate for normal ripening, while the levels in the control group were excessively high, inducing CI symptoms.

PRACTICAL APPLICATIONS

Refrigeration is a technique that can be used to extend shelf life of yellow pitaya fruit. Nevertheless, these fruits are susceptible to chilling injury. This research was developed to study the effect of heat shock treatment on the preservation of whole yellow pitaya fruit during refrigeration. Preheating fruit at 25C for 24 h before storage at 2C for 14 days prevented chilling injury during shelf life at 18C. Thus, the combination of heat shock and refrigeration delays the senescence of yellow pitaya fruit and therefore improves its shelf life. Furthermore, this treatment could be useful during quarantine treatments of fruit fly‐infested fruit.

     

ESTIMATION of HEAT of MOISTURE SORPTION and IMPROVED CRITERIA FOR EVALUATING MOISTURE SORPTION ISOTHERM EQUATIONS FOR FOODS

Heat of sorption of moisture on foods can be estimated from sorption isotherm equations having both moisture and temperature as independent variables. Sorption thermodynamics dictate that the heat of moisture sorption should decrease with increased moisture concentration, or increased temperature of food, provided no biological, chemical or other changes occur during sorption. This fact, and the Clausius-Clapeyron equation were used to derive two analytical formulae to evaluate the reliability of moisture sorption equations in the calculation of heat of sorption. As examples, Chung and Pfost, modified Harkins and Jura, modified Henderson, and Guggenheim-Anderson-De Boer equations at specified conditions were analyzed.