A Comparison of Three Methods for Determining Thermal Inactivation Kinetics: A Case Study on Salmonellaenterica in Whole Milk Powder

2020 ◽  
Author(s):  
Soon Kiat Lau ◽  
Xinyao Wei ◽  
Nina Kirezi ◽  
Rajendra Panth ◽  
Arena See ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Thermal Inactivation ◽  
Milk Powder ◽  
Water Bath ◽  
Isothermal Treatment ◽  
Inactivation Kinetics ◽  
Model Parameters ◽  
Treatment Methods ◽  
Whole Milk ◽  
Whole Milk Powder

Different methods for determining the thermal inactivation kinetics of microorganisms could result in discrepancies of the resulting thermal resistance values. This study determined the thermal resistance of Salmonella in whole milk powder using three methods (Thermal death time (TDT) disk in water bath, pouches in water bath, and TDT Sandwich). Samples from three separate production lots of whole milk powder were inoculated with a five strain Salmonella cocktail and equilibrated to 0.20 a w . The samples were then subjected to three isothermal treatment methods at 75, 80, or 85 °C. Samples were taken out at six timepoints and enumerated for survivors. The inactivation data were fitted to two consolidated models consisting of two primary models (log-linear and Weibull) and one secondary model (Bigelow). Normality testing indicated that all the model parameters were normally distributed. None of the model parameters for both consolidated models were significantly different (α=0.05). The amount of inactivation during the come-up time phase was also not significantly different among the methods (α=0.05). In terms of magnitude, however, the TDT Sandwich showed less inactivation during the come-up time phase and overall less variation in model parameters. The survivor data from all three methods were combined and fitted to both consolidated models, with the Weibull having lower root mean square error and a better fit according to corrected Akaike’s Information Criterion. These results suggest that the three thermal treatment methods are not significantly different from each other and are interchangeable, at least in the case of Salmonella in whole milk powder. Comparisons with more methods, other microorganisms, and larger varieties of food products using the same framework presented in this study could provide guidance for standardizing thermal inactivation kinetics studies for microorganisms in foods.

Effects of Inoculation Procedures on Variability and Repeatability of Salmonella Thermal Resistance in Wheat Flour

2016 ◽  
Vol 79 (11) ◽  
pp. 1833-1839 ◽  
Author(s):  
IAN M. HILDEBRANDT ◽  
BRADLEY P. MARKS ◽  
ELLIOT T. RYSER ◽  
ROSSANA VILLA-ROJAS ◽  
JUMING TANG ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Water Activity ◽  
Wheat Flour ◽  
Thermal Inactivation ◽  
Culture Method ◽  
Isothermal Treatment ◽  
Inactivation Kinetics ◽  
Inoculation Methods ◽  
Low Moisture Foods ◽  
D Values

ABSTRACT Limited prior research has shown that inoculation methods affect thermal resistance of Salmonella in low-moisture foods; however, these effects and their repeatability have not been systematically quantified. Consequently, method variability across studies limits utility of individual data sets and cross-study comparisons. Therefore, the objective was to evaluate the effects of inoculation methodologies on stability and thermal resistance of Salmonella in a low-moisture food (wheat flour), and the repeatability of those results, based on data generated by two independent laboratories. The experimental design consisted of a cross-laboratory comparison, both conducting isothermal Salmonella inactivation studies in wheat flour (~0.45 water activity, 80°C), utilizing five different inoculation methods: (i) broth-based liquid inoculum, (ii) lawn-based liquid inoculum, (iii) lawn-based pelletized inoculum, (iv) direct harvest of lawn culture with wheat flour, and (v) fomite transfer of a lawn culture. Inoculated wheat flour was equilibrated ~5 days to ~0.45 water activity and then was subjected to isothermal treatment (80°C) in aluminum test cells. Results indicated that inoculation method impacted repeatability, population stability, and inactivation kinetics (α = 0.05), regardless of laboratory. Salmonella inoculated with the broth-based liquid inoculum method and the fomite transfer of a lawn culture method exhibited instability during equilibration. Lawn-based cultures resulted in stable populations prior to thermal treatment; however, the method using direct harvest of lawn culture with wheat flour yielded different D-values across the laboratories (α = 0.05), which was attributed to larger potential impact of operator variability. The lawn-based liquid inoculum and the lawn-based pelletized inoculum methods yielded stable inoculation levels and repeatable D-values (~250 and ~285 s, respectively). Also, inoculation level (3 to 8 log CFU/g) did not affect D-values (using the lawn-based liquid inoculum method). Overall, the results demonstrate that inoculation methods significantly affect Salmonella population kinetics and subsequent interpretation of thermal inactivation data for low-moisture foods.

Reproducibility of Salmonella Thermal Resistance Measurements via Multilaboratory Isothermal Inactivation Experiments

2020 ◽  
Vol 83 (4) ◽  
pp. 609-614 ◽  
Author(s):  
IAN M. HILDEBRANDT ◽  
BRADLEY P. MARKS ◽  
NATHAN M. ANDERSON ◽  
ELIZABETH M. GRASSO-KELLEY
Keyword(s):  
Thermal Resistance ◽  
Thermal Inactivation ◽  
Isothermal Treatment ◽  
Inactivation Kinetics ◽  
Sampling Point ◽  
Single Location ◽  
Isothermal Analysis ◽  
D Values ◽  
Log Linear ◽  
Treatment Medium

ABSTRACT Isothermal inactivation experiments often are used to investigate the thermal resistance of pathogens, such as Salmonella, in foods; however, little is known about the reproducibility of such experimental methodologies. The objective of this study was to quantify the reproducibility of Salmonella isothermal resistance results via a six-laboratory comparison. Inoculation was performed at a single location and then distributed to each laboratory for isothermal analysis. Salmonella Agona 447967 was inoculated into oat flour, re-equilibrated to a water activity (aw) of 0.45, and then packaged and distributed to each laboratory. Before conducting the inactivation trials, each laboratory was required to verify the inoculated product's aw, enumerate Salmonella population levels, and verify that the isothermal treatment medium was at the target temperature (80°C). All laboratories were required to process at least three replications, collect at least six sample time points with three subsamples at each sampling point, enumerate survivors using an identical plating methodology and media, and verify that the temperature did not substantially change during isothermal treatment. The log-linear model was fit to the Salmonella survivor data, and the resultant D-values were statistically compared via Welch's t test (α = 0.05). Two significant differences in thermal inactivation kinetics were identified as potentially resulting from suspected methodology deviations. Two of the inoculated batches distributed for analysis yielded significantly lower D-values, which likely resulted from a deviation in the inoculation procedures. One laboratory yielded significantly lower D-values, which was likely the result of temperature deviations. Overall, excluding the D-values resulting from deviations, the inactivation results were reproducible, yielding D-values of 30.2 ± 3 min. These results indicate that isothermal inactivation results can be reproducible but that even minor methodology deviations can substantially affect measured Salmonella thermal resistance. HIGHLIGHTS

Survival and thermal resistance of Salmonella in dry and hydrated nonfat dry milk and whole milk powder during extended storage

2021 ◽  
Vol 337 ◽  
pp. 108950
Author(s):  
Amninder Singh Sekhon ◽  
Arshdeep Singh ◽  
Phoebe Unger ◽  
Monipel Babb ◽  
Yaeseol Yang ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Milk Powder ◽  
Whole Milk ◽  
Dry Milk ◽  
Nonfat Dry Milk ◽  
Whole Milk Powder

Adhesion characteristics of whole milk powder to a stainless steel surface

1998 ◽  
Vol 97 (3) ◽  
pp. 191-199 ◽  
Author(s):  
Paul R. Rennie ◽  
X.D. Chen ◽  
Antony R. Mackereth
Keyword(s):  
Stainless Steel ◽  
Steel Surface ◽  
Milk Powder ◽  
Stainless Steel Surface ◽  
Whole Milk ◽  
Whole Milk Powder

DRIED MILK POWDER: II. FACTORS AFFECTING THE SORPTION OF CARBON DIOXIDE

1945 ◽  
Vol 23f (6) ◽  
pp. 327-333 ◽  
Author(s):  
Jesse A. Pearce
Keyword(s):  
Carbon Dioxide ◽  
Milk Powder ◽  
Sorption Rate ◽  
High Fat ◽  
Time Intervals ◽  
Sorption Behaviour ◽  
Factors Affecting ◽  
Whole Milk ◽  
Identical Manner ◽  
Whole Milk Powder

Sorption of carbon dioxide by milk powder in a closed system at 35 °C. and at approximately 74 cm. of mercury was observed to be greater than 0.4 cc. per gm. after 150 hr., while only 0.012 cc. of nitrogen was absorbed per gm. after 70 hr. The initial sorption of carbon dioxide varied with time according to the equation:[Formula: see text]where s is 100 times the amount sorbed in cc. per gm. at any time, t (min.), and k and m are constants peculiar to the system under investigation. The logarithmic form of this equation was used. Powders with 26, 28, and 30% fat did not differ in behaviour, but sorption curves for powders with only 1% fat had lower [Formula: see text] values and lower [Formula: see text] values than the curves for the high fat levels. Powders with 1% fat sorbed carbon dioxide in an identical manner when exposed to either 100% carbon dioxide or a mixture of 20% carbon dioxide and 80% nitrogen. For whole milk powder, dilution to 80% nitrogen content was effective in reducing the initial sorption rate of carbon dioxide. Great variation was observed in the sorption behaviour of powders from different plants and in powders produced at different time intervals in the same plant. Temperature differences within the range 25° to 40 °C. had no effect on sorption. Palatability and [Formula: see text] correlated to the extent of r =.61.

scholarly journals Effect of bovine feeding system (pasture or concentrate) on the oxidative and sensory shelf life of whole milk powder

2021 ◽  
Author(s):  
H.J. Clarke ◽  
C. Griffin ◽  
D. Hennessy ◽  
T.F. O'Callaghan ◽  
M.G. O'Sullivan ◽  
...  
Keyword(s):  
Shelf Life ◽  
Milk Powder ◽  
Feeding System ◽  
Whole Milk ◽  
Whole Milk Powder

A Process for Increasing the Free Fat Content of Spray-dried Whole Milk Powder

2003 ◽  
Vol 68 (1) ◽  
pp. 210-216 ◽  
Author(s):  
A.B. Koc ◽  
P.H. Heinemann ◽  
G.R. Ziegler
Keyword(s):  
Milk Powder ◽  
Fat Content ◽  
Whole Milk ◽  
Whole Milk Powder ◽  
Spray Dried
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