Authors:Pinar Şanlibaba, S. Buzrul, Nefİse Akkoç, H. Alpas and M. Akçlİk
Survival curves of
bacteriophage pll98 inactivated by heat were obtained at seven temperature values (50–80°C) in M17 broth and skim milk. Deviations from first-order kinetics in both media were observed as sigmoidal shapes in the survival curves of pll98. An empirical model with four parameters was used to define the thermal inactivation. Number of parameters of the model was reduced from four to two in order to increase the robustness of the model. The reduced model produced comparable fits to the full model. Both the survival data and the calculations done using the reduced model (time necessary to reduce the number of phage pll98 six- or seven- log10) indicated that skim milk is a more protective medium than M17 broth within the assayed temperature range.
Authors:K. Karimi, A. Narmani, I. Pertot and M. Arzanlou
Proteases constitute a significant part of cell wall-degrading enzymes (CWDEs)
produced by fungal biocontrol agents and particularly crucial in mycoparasitism
of fungal phytopathogens. Plate-based screening methods are routinely used for
screening protease-producing microorganisms including fungi. Skim milk agar
(SMA) is one of the most popular media for the detection of protease producing
bacteria. However, SMA is not efficient to test fast growing fungi, because it
does not give an estimation of the actual amount of secreted protease produced
by fungal inocula. In the current study, the efficacy of two modified
plate-screening methods, including split-SMA (SSMA) and minimal medium
supplemented with skim milk (MSMW) was assessed for detection of protease
production by three representative fungal strains including Trichoderma
longibrachiatum strain N, Beauveria bassiana
strain B and Purpureocillium lilacinum strain PL. Protease
production was revealed on the three tested media by the three strains. However,
the halo diameter of the fungal strains (a proxy for protease production) was
the smallest on SMA. Furthermore, protease production could not be detected for
T. longibrachiatum strain N on SMA due to its fast growth;
while it showed the highest protease activity on both modified media compared
with the other strains. According to the result of this study, the SSMA medium
is an easy and more accurate method compared with the two other different
methods as it displays the actual amount of protease produced by fungal strains
and therefore this method is recommended for quantitative and qualitative
detection of protease production by slow and fast growing fungi.
production by lactic acid bacteria and bifidobacteria grown in skimmilk containing honey. Fd Microbiol. Safety , 66 , 478-481.
Growth and acid production by lactic acid bacteria and bifidobacteria grown in skimmilk containing
Authors:Ander Arando, Juan Vicente Delgado, José Manuel León, Sergio Nogales, Francisco Javier Navas-González, María Gabriela Pizarro and Carlos Carmelo Pérez-Marín
Allai , L. , Druart , X. , Contell , J. , Louanjli , N. , Moula , A. B. , Badi , A. , Essamadi , A. , Nasser , B. and El Amiri , B. ( 2015 ): Effect of argan oil on liquid storage of ram semen in Tris or skimmilk based extenders
A L-QADIRI , H.M. , L IN , M. , A L-HOLY , M.A. , C AVINATO , A.G. & R ASCO , B.A. ( 2008 ): Monitoring quality loss of pasteurized skimmilk using visible and short wavelength near-infrared spectroscopy and multivariate analysis . J
Authors:Y. H. Roos, K. Jouppila and Bettina Zielasko
An exotherm, observed in differential scanning calorimetry (DSC) scans of amorphous food materials above their glass transition temperature,Tg, may occur due to sugar crystallization, nonenzymatic browning, or both. In the present study, this exothermal phenomenon in initially anhydrous skim milk and lactose-hydrolyzed skim milk was considered to occur due to browning during isothermal holding at various temperatures above the initialTg. The nonenzymatic, Maillard browning reaction produces water that in amorphous foods, may plasticize the material and reduceTg. The assumption was that quantification of formation of water from theTg depression, which should not be observed as a result of crystallization under anhydrous conditions, can be used to determine kinetics of the nonenzymatic browning reaction. The formation of water was found to be substantial, and the amount formed could be quantified from theTg measured after isothermal treatment at various temperatures using DSC. The rate of water formation followed zero-order kinetics, and its temperature dependence well aboveTg was Arrhenius-type. Although water plasticization of the material occurred during the reaction, and there was a dynamic change in the temperature differenceT−Tg, the browning reaction was probably diffusioncontrolled in anhydrous skim milk in the vicinity of theTg of lactose. This could be observed from a significant increase in activation energy. The kinetics and temperature dependence of the Maillard reaction in skim milk and lactose-hydrolyzed skim milk were of similar type well above the initialTg. The difference in temperature dependence in theTg region of lactose, but above that of lactose-hydrolyzed skim milk, became significant, as the rate in skim milk, but not in lactose-hydrolyzed skim milk, became diffusion-controlled. The results showed that rates of diffusion-controlled reactions may follow the Williams-Landel-Ferry (WLF) equation, as kinetic restrictions become apparent within amorphous materials in reactions exhibiting high rates at the same temperature under non-diffusion-controlled conditions.
The effect of growth phase of cells, cryoprotectant agents and freezing rate on the survival of selected micro-organisms (Bacillus cereus, Lactobacillus plantarum, Escherichia coli, Pseudomonas fluorescens, Saccharomyces cerevisiae, Kluyveromyces lactis, Candida utilis, Mucor racemosus, Aspergillus niger) during freezing and thawing was studied. In cases where significant differences were observed stationary phase cells always survived better than exponential phase ones, while of the two cryoprotectant agents studied, horse serum + inositol was always superior to skimmed milk powder + inositol. The effect of freezing rate was different among the studied micro-organisms.
Microbial properties, correlation between pH and microbial properties, and the effect of pH adjustment on microflora of Civil cheese during refrigerated storage were examined. The cheeses made from skim milks with a pH of 5.35, 5.30, and 5.25 had higher counts of total aerobic bacteria, yeast and moulds, LAB and psychrotrophic organisms than those made from milks adjusted to higher pH values. A highly negative correlation between pH and total aerobic bacteria, yeast and moulds and LAB was observed in Civil cheese.
The -emitter32P was used to determine total phosphorus by INAA in Skim Milk Powder RM 63, a material now certified by the EEC Bureau of Reference (BCR). Samples and comparator were irradiated in the Danish reactor DR 3. One month later the samples were dissolved in water and aliquots counted with a GM end-window counter using absorber thicknesses of zero to 400 mg/cm2. The Synthesis of Precision was introduced to find the absorber best suited for discriminating against other -emitting isotopes and at the same time giving maximum precision.