Contents
01.12.2011.
Professional paper
Effects of Pretreatments in Convective Dehydration of Rosehip (Rosa eglanteria)
The aim of this work was to experimentally determine drying curves for thin layer and bed drying of rosehip fruits, with and without pretreatments, to reduce processing times as a function of drying air operating variables, to propose dehydration kinetics of fruits and to determine its kinetic parameters for further use within drying simulation software. Fruits were pre-treated both chemically and mechanically, which included dipping the fruits in NaOH and ethyl oleate solutions; and cutting or perforating the fruit cuticle, respectively. Simulation models were then adopted to fit the kinetics drying data considering fruit volume shrinkage. These simple models minimized the calculation time during the simulation of deep-bed driers. Results show that pre-treatments reduced processing times up to 57%, and evaluated models satisfactorily predicted the drying of rosehip fruit. Effective mass diffusion coefficients were up to 4-fold greater when fruit was submitted to mechanical pretreatments.
Alejandra Mabellini, Elizabeth Ohaco, Carlos Alberto Márquez, Antonio De Michelis, Jorge Enrique Lozano
01.12.2011.
Professional paper
Influence of Organic Material and Biofilms on Disinfectant Efficacy Against Listeria monocytogenes
The effects of organic material and biofilm formation on the efficacy of Suma Tab D4 chlorine tablets and Suma Bac D10 quaternary ammonium compound (QAC) against Listeria monocytogenes was determined in suspension and on stainless steel and polystyrene surfaces according to standard disinfectant test methodology. Exposure to 200 and 740 mg L-1 QAC and to 150 mg L-1 active chlorine resulted in a > 5.0 log10 CFU mL-1 and > 5.0 log10 CFU/coupon reduction of six L. monocytogenes strains within one minute, in suspension tests, and on stainless steel surfaces, respectively. Additionally, there was a reduction by as much as 5 log10 CFU/coupon or 5 log10 CFU/well of reference strains EGDe and Scott A biofilms within five minutes on stainless steel and polystyrene surfaces. Organic material, added as bovine serum albumin at 0.3% (w/v) completely prevented the inactivation of L. monocytogenes in 150 mg L-1 chlorine, while reductions of only 0.6 +- 0.1 log10 CFU mL-1 were recorded in the presence of UHT milk at 3% (v/v). In contrast, reductions of 5 log10 CFU mL-1 were recorded within one minute on exposure to 740 mg L-1 QAC in the presence of 0.3% (w/v) bovine serum albumin and within two minutes in the presence of 20 % (v/v) UHT milk. Although Suma D4 chlorine tablets and Suma Bac D10 QAC are effective listericidal agents at recommended concentrations, Suma Tab D4 chlorine efficacy against L. monocytogenes is impaired by the presence of low concentrations of organic material, while Suma Bac D10 QAC maintains its listericidal activity in high organic loads.
Hilda Nyati, Rijkelt Beumer, Stijn Van der Veen, Wilma Hazeleger, Tjakko Abee
01.12.2011.
Professional paper
Effect of Egg White Utilization on the Physico-Chemical and Sensory Attributes of Protein-rich Yoghurt
High protein yoghurt was made from whole milk, fortified with egg white (30% v/v) and skim milk powder at 12% (w/v). Different yoghurt mixes, with albumin content of 15%, 30% and 45% (v/v), were prepared. The control was made from whole milk, fortified with skim milk powder at 12% (w/v). The blended premixes were pasteurized at 74ºC for 4 seconds, cooled and then inoculated with 3% (w/v) Direct Vat Set yoghurt starter culture at 45ºC. After fermentation for 3 hours in a water bath maintained at 46+-1C, product was cooled to 5ºC and then stored for 24 hours. The effect of the fortification on physico-chemical and sensory properties was investigated. Protein content increased to 8.50% at 45% egg white utilization. Susceptibility to wheying was reduced in egg-white fortified samples, without signicant difference in sensory attributes of the test samples compared to the control. Sensory analysis showed that yoghurt fortified with 45% egg white was organoleptically acceptable. The yoghurt was rated as having better sensory appeal as compared to the control.
Lilian A Gogo, Kennedy O. Gogo, Peter L. Shalo, Symon Maina Mahungu
