Effect of protein–polysaccharide mixtures on the continuous manufacturing of foamed food products

The aim of this work is to understand the effects of protein and polysaccharide interactions on the physicochemical properties of highly viscous Newtonian model foods and their impact on continuous foaming operation in laminar flow conditions. Model foods consisted of modified glucose syrups. Foaming was carried out at constant gas-to-liquid flow rate ratio as a function of rotation speed. Overrun, mean bubble diameter d₃₂ and stability over time were used to characterize foams. Results showed that blow-by occurred during foaming of models including either 0.1% guar or xanthan without proteins, while 0.1% pectin allowed a total incorporation of the gas phase with large bubbles. For proteins, models with 2% whey protein isolate (WPI) were able to form foams with the desired overrun and small bubbles, while foaming was less effective with 2% Na-caseinates. With WPI, guar addition did not improve significantly foam properties. Overrun was reduced in WPI–xanthan mixtures, probably because the matrix exhibited viscoelastic trends even though xanthan decreased d₃₂. WPI–pectin mixtures provided abundant and stable foams with the smallest d₃₂ and the best stability because WPI reinforced the time-dependent behaviour of pectin recipes. However, blow-by was observed with 0.1% pectin when WPI was replaced by Na-caseinates, which demonstrates the key role of specific protein–polysaccharide interactions on overrun. Conversely, bubble diameters in foams were governed by process parameters and could be adequately described using a laminar Weber number based on foam viscosity measured during foaming for all model foods that provided stable foams.     

Incidence of Listeria monocytogenes in cheese manufacturing plants from the northeast region of São Paulo, Brazil

The incidence of Listeria monocytogenes in three cheese manufacturing plants from the northeastern region of S?o Paulo, Brazil, was evaluated from October 2008 to September 2009. L. monocytogenes was found in samples from two plants, at percentages of 13.3% (n = 128) and 9.6% (n = 114). Samples of raw and pasteurized milk, water, and Minas Frescal cheese were negative for L. monocytogenes, although the pathogen was isolated from the surface of Prato cheese and in brine from one of the plants evaluated. L. monocytogenes was also isolated from different sites of the facilities, mainly in non-food contact surfaces such as drains, floors, and platforms. Serotype 4b was the most predominant in the plants studied. The results of this study indicate the need for control strategies to prevent the dispersion of L. monocytogenes in the environment of cheese manufacturing plants.     

Influence and comparison of emerging techniques of yarn manufacturing on physical–mechanical properties of polyester-/cotton-blended yarns and their woven fabrics

Abstract

In this study, the physical–mechanical properties of ring spun, ring compact, rotor and air-vortex yarns were investigated. The study was carried with yarn having linear densities of 24.4 tex and 36.7 tex, which were then converted to woven fabrics. The ring spun yarns have higher values of strength but also with higher strength irregularities. Extra-ordinarily low hairiness was observed in air-vortex yarns due to its unique yarn formation technique. The deviation rate (DR) of yarns have correlation with the mass spectrogram of respective yarns obtained from USTER Tester 5. Rotor and air-vortex yarns exhibited higher coefficient of friction. The woven fabrics made from ring spun yarns exhibited higher tensile and tear strength with higher elongation at break. The fabrics made from air-vortex yarns have very good pilling grade due to less protruding fibres on their surface and good structural integrity.     

The influence of manufacturing and drying conditions on the survival and toxinogenesis of Staphylococcus aureus in two Spanish dry sausages (chorizo and salchichón)

The effects of formulation, starter culture and fermentation temperature on growth and synthesis of toxin A (SEA) and TNase by Staphylococcus aureus during fermentation and drying of Spanish chorizo were investigated. Inhibitory factors able to inhibit SEA synthesis in culture media were unable to prevent SEA production in chorizo fermented at 20 and 30°C, though a lower temperature and starter culture SP318 (Lactobacillus sake, Pediococcus pentosaceous and Staphylococcus xylosus) decreased staphylococcal growth and SEA formation. Reduction and even disappearance of the SEA during ripening was observed. In most batches, TNase was a reliable indicator of staphylococcal growth and SEA production. Dextrose added to the salchichón formulation repressed S. aureus growth during drying. Lactobacillus curvatus in combination with dextrose was an effective anti-staphylococcal agent during fermentation.