Survivability of Salmonella Pathogens and Physicochemical Characteristics of Powder Goat Milk Stored under Different Storage Treatment Regimens

Roshan Paswan,Young W Park,Abhinav Mishra

doi:10.3390/dairy1030018

Roshan Paswan, Young W Park + Show 1 more

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https://doi.org/10.3390/dairy1030018

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Abstract

Survivability of Salmonella pathogens in commercial powdered goat milk (PGM) under different storage treatments was investigated using three batches of PGM products stored at two temperatures (4 °C and 25 °C) and ten storage periods (0, 3, 7, 14, 21, 30, 60, 90, 120 and 180 days). A cocktail of three Salmonella serotypes (Salmonella agona, Salmonella enteritidis and Salmonella tennessee) was inoculated to the PGM samples and then survival of Salmonella counts was enumerated in the inoculated and non-inoculated control groups. Results showed that the initial Salmonella counts were 7.103 Log CFU (colony forming unit)/g at both temperatures. At the first 3 days, the viable Salmonella counts were reduced about 0.94 and 1.40 Log CFU/g at 4 °C and 25 °C, respectively, where the same levels were sustained for 14 days. Further reductions continued and at the end of 180 days storage, Salmonella survivability was 1.15 Log CFU/g higher at 4 °C than at 25 °C under the same water activity condition. As the storage period advanced, viable pathogen counts were gradually decreased. The pH of samples stored at 4 °C for 0 and 4 month were higher than those stored at 25 °C except for 2 months, while no differences were found in water activity (aw) between treatments of the PGM products. With regard to physicochemical characteristics, the samples stored at 25 °C showed higher POV (peroxide value) values than those stored at 4 °C for 2 and 4 month periods, indicating that the rate of lipid oxidation in the PGM was elevated by a higher storage temperature and a longer storage period. The basic nutrient compositions of the experimental PGM were similar to those reported in recent studies. Oleic acid (C18:1) was the highest, caprylic acid (C8:0) was the second highest, and behenic acid (C22:0) was the lowest concentration among all fatty acids identified in the PGM samples. Most of the fatty acid concentrations tended to decrease with advanced storage periods. This research indicates that the survivability of Salmonella pathogens in the PGM products stored at 4 °C for 180 days was higher than those stored at 25 °C under the same aw condition.

Highlights

The advantages of powdered milk are the extension of shelf-life of the milk and convenient transport through reduced volume [1,2]
Peroxide Value (POV) values than those stored at 4 ◦ C for 2 and 4 month periods, indicating that the rate of lipid oxidation in the powdered goat milk (PGM) was elevated by a higher storage temperature and a longer storage period
In terms of survivability of Salmonella pathogens in the powdered goat milk during the 6 month storage, the general declining trend of the pathogen counts was similar for both temperature treatments at 4 ◦ C and 25 ◦ C

Summary

Introduction

The advantages of powdered milk are the extension of shelf-life of the milk and convenient transport through reduced volume [1,2]. In terms of food safety, dehydrated milk has the advantage of limited growth of pathogenic and spoilage bacteria [3]. Outbreaks of Salmonella serotypes (Salmonella agona, Salmonella tennessee) [10,11] were linked to dry milk products, which indicates the importance for specific study on the microbial safety of different species in milk powder. In addition to these overall outbreaks, incidents of foodborne illness linked to consumption of dry foods are largely caused by Salmonella as compared to other pathogens [12]

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