Effect of Curd Washing Level on Proteolysis and Functionality of Low-Moisture Mozzarella Cheese Made with Galactose-Fermenting Culture

Abstract: The effect of curd washing on functional properties of low-moisture mozzarella cheese made with galactose-fermenting culture was investigated. A total of 4 curd washing levels (0%, 10%, 25%, 50% wt/wt) were used during low-moisture mozzarella cheese manufacture, and cheeses were stored for 63 d at 4 °C and the influence of curd washing on proteolysis and functionality of low-moisture mozzarella cheese were examined. Curd washing had a significant effect on moisture and ash contents. In general, moisture contents increased and ash contents decreased with increased curd washing levels. Low-moisture mozzarella cheese made with 10% curd washing levels showed higher proteolysis, meltability, and stretchability during storage than other experimental cheeses. In general, galactose contents decreased during storage; however, cheeses made with 25% and 50% curd washing levels had lower galactose contents than those with control or 10%. L*-values (browning) decreased and proteolysis increased in low-moisture mozzarella cheeses during storage.     

Effects of extended dry storage of powdered infant milk formula on susceptibility of Enterobacter sakazakii to hot water and ionizing radiation

Infant milk formula has been identified as a potential source of Enterobacter sakazakii, which has been implicated in neonatal meningitis and necrotizing enterocolitis. This study was undertaken to determine whether the length of E. sakazakii storage in powdered infant milk formula (PIMF) affected the ability of the pathogen to survive subsequent reconstitution of the powder with hot water or treatment with gamma radiation. Five E. sakazakii strains were mixed individually with PIMF and kept for up to 12 months at 25 degrees C. After storage PIMF was reconstituted with water at 60 to 100 degrees C or was exposed to < or = 5 kGy of gamma radiation. Without any treatment secondary to drying, E. sakazakii counts decreased < 1 log/g after 1 month but decreased about 4 log/g during storage for 8 to 12 months. Dry storage decreased thermal resistance but increased resistance of E. sakazakii to ionizing radiation in PIMF. Reconstitution of contaminated powder with water at 70 degrees C after 1 month of dry storage reduced E. sakazakii viability slightly, > 2 log/g, and after powder was stored for 12 months all E. sakazakii strains were eliminated. In contrast, desiccation substantially increased the resistance of E. sakazakii strains to ionizing radiation. Although the D-value for E. sakazakii IMF1 following overnight storage in PIMF was 0.98 kGy, > 4 kGy was required to kill 1.5 log/g of the same strain that had survived 12 months in dry PIMF. Results suggested that low-dose irradiation will more effectively eliminate E. sakazakii from PIMF if the treatment is applied shortly after PIMF manufacture.     

Effect of chemical modification of oil fly ash and compatibilization on the rheological and morphological properties of low‐density polyethylene composites

In this study, the effect of oil fly ash (OFA), a by‐product of oil fuel power plants, on the rheological and morphological behavior of low‐density polyethylene (LDPE) is investigated. As received and acid‐functionalized OFA (COOH‐OFA) are used to examine the effect of surface modification of OFA on polymer–filler composites. LDPE/OFA composites were prepared by melt mixing with filler loading in the range 1–10 wt %. The results are compared with pure LDPE. The effect of polyethylene‐grafted‐maleic anhydride (PE‐g‐MA) as a compatibilizer was also studied. Both viscous and elastic properties of composites increased with OFA loading especially at low frequency. The surface modification of OFA has influenced the properties of OFA. As‐received OFA showed some agglomeration at high loading that resulted in two‐phase system as described by scanning electron microscopy (SEM) and Cole–Cole plot. Field emission‐SEM (FE‐SEM) images showed improvement in the dispersion of COOH‐LDPE/OFA composites. In addition, the surface modification reduced the size of agglomeration. In general, the COOH modification of OFA improved both the dispersion and rheological properties of OFA. With chemical modification, the concentration of the filler can be increased to 10% without compromising the properties of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Hydrometallurgical extraction of zinc from Jordanian electric arc furnace dust

Zinc was extracted in a Jordanian Steel Plant using an electric arc furnace dust. Sulfuric, nitric and hydrochloric acids were used at different concentrations to recover zinc from dust particles. The highest zinc extraction was obtained at low acid concentration of less than 1 mol/L in the order of H₂SO₄ followed by HNO₃ and then HCl. The kinetics of zinc extraction using H₂SO₄ showed a maximum zinc recovery of 72% obtained by using 0.1 mol/L acid concentration, 900 rpm agitation speed and 50 °C.     

Sensory Evaluation of Flavored Soy Milk-Based Yogurt： A Comparison between Jordanian and Malaysian Consumers

Soy yogurt has gained significant popularity due to its nutritional health benefits. The objectives of this study were to develop flavored yogurt from soybean milk with reduced soy aftertaste by the addition of 30% （wt/wt） strawberry or orange jam in conjunction with a lactic acid fermentation. Soy milk-based yogurt products were assessed for microbial quality and for acceptability by a panel of Jordanian and Malaysian consumers. Sixty-one individuals, of whom 75.4% （n = 46） were Jordanian and 24.6% （n = 15） were Malaysian, evaluated the plain and flavored soy milk-based yogurt. The overall acceptability of orange and strawberry soy yogurt was rated significantly higher than plain soy yogurt. In general, the orange and strawberry soy yogurt received higher sensory ratings from Malaysian than Jordanian consumers. In addition, formulations with orange jam received higher scores than those flavored with strawberry. Shelf life tests showed that soy yogurt was acceptable for at least 8 d without perceptible spoilage. Therefore, the approach used yielded flavored products with better acceptability and improved sensory attributes, including decreased intensity of off flavor, with suitable shelf life at 4 ℃.     

Impact of environmental stress desiccation, acidity, alkalinity, heat or cold on antibiotic susceptibility of Cronobacter sakazakii

Cronobacter sakazakii is an emerging foodborne pathogen that has been implicated in severe forms of meningitis, septicemia or necrotizing colitis in pre-term neonates. Although illness outbreaks (primarily associated with powdered infant formula, PIF) caused by this pathogen are rare, the case-fatality rate may reach 50%. Successful treatment of C. sakazakii infection is reliant upon clinical use of antibiotics (AB) such as ampicillin. Recent reports showed increased resistance of C. sakazakii to broad-spectrum antibiotics. The objective of this study was to evaluate the effect of extreme pH (3.5 for 30 min or 11.25 for 5 min), cold (4 °C for 24 h), heat (55 °C for 5 min), and desiccation (cells were dried at 40 °C for 2 h and held at 21 °C for 4 d) stresses on susceptibility of five isolated strains of C. sakazakii to streptomycin, gentamicin, kanamycin, neomycin, tetracycline, doxycycline, tilmicosin, florfenicol, ampicillin, amoxicillin, vancomycin, ciprofloxacin and enrofloxacin. All unstressed strains of C. sakazakii were sensitive to streptomycin, gentamycin, kanamycin, ciprofloxacin, enrofloxacin, ampicillin and amoxicillin, but were moderately resistant or resistant to the rest. Exposing cells to alkaline or acidic stress did not change their sensitivity toward streptomycin, gentamycin, kanamycin or ciprofloxacin, but their resistance toward the other AB was increased. Cells stressed by desiccation showed increased sensitivity toward streptomycin, gentamicin, kanamycin, ciprofloxacin, enrofloxacin, ampicillin and doxycycline, but showed resistance toward the others. Cold-stressed cells were more sensitive to streptomycin, gentamicin, kanamycin, and ciprofloxacin compared with heat-stressed cells, but both heat and cold-stressed cells showed increased resistance toward all the other AB. Results obtained will help in understanding the effect of environmental stresses during processing on C. sakazakii susceptibility to AB.