Heat-Resistant Psychrotrophic Bacteria Isolated from Pasteurized Milk1

1977 ◽  
Vol 40 (2) ◽  
pp. 101-108 ◽  
Author(s):  
C. J. WASHAM ◽  
H. C. OLSON ◽  
E. R. VEDAMUTHU
Keyword(s):  
Thermal Resistance ◽  
Shelf Life ◽  
Detailed Examination ◽  
Genus Bacillus ◽  
Pasteurized Milk ◽  
Psychrotrophic Bacteria ◽  
Milk Samples ◽  
Heat Resistant ◽  
Different Types

Psychrotrophic bacteria were isolated from 227 pasteurized milk samples which had a shelf life in excess of 20 days at 7.2 C. Of 700 cultures isolated, 135 were resistant to heating at 72 C for 16 sec and were able to re-establish growth at 7.2 C. Thirty-five cultures, representing 15 different types were subjected to detailed examination to determine their actions on refrigerated milk, growth temperatures, thermal resistance at various temperatures, and their identities. The spore-forming genus Bacillus occured most frequently. The non-sporing types were assigned to the genera Arthrobacter, Microbacterium, Streptococcus, and Corynebacterium.

Evaluation of an 18°C/45-Hour Plate Count Technique for the Enumeration of Psychrotrophic Bacteria in Raw and Pasteurized Milk

1983 ◽  
Vol 46 (6) ◽  
pp. 528-529 ◽  
Author(s):  
HARRY K. OEHLRICH ◽  
ROBIN C. MCKELLAR
Keyword(s):  
Plate Count ◽  
Reliable Estimate ◽  
Additional Test ◽  
Bacterial Counts ◽  
Pasteurized Milk ◽  
Psychrotrophic Bacteria ◽  
Milk Samples

Bacterial counts were done at 7°C for 10 d and at 18°C for 45 h on 93 samples of raw and 185 samples of pasteurized milk. As an additional test, catalase-positive microorganisms were enumerated at 18°C/45 h. Close correlations were obtained between the numbers of microorganisms following 18°C/45-h and 7°C/10-d incubations in raw (r2=0.866) and pasteurized (r2=0.936) milk samples. Similar correlations (r2=0.860 and 0.946) were noted for the 18°C/45-h-catalase and the 7°C/10-d methods for raw and pasteurized milk, respectively. Results suggest that incubation at 18°C for 45 h provides a reliable estimate of the numbers of psychrotrophs in raw and pasteurized milk and that the use of catalase does not improve sensitivity of the test significantly.

scholarly journals Influence of the microbiological quality of raw milk on the shelf life of pasteurized milk

2019 ◽  
Vol 40 (4) ◽  
pp. 1469
Author(s):  
José Carlos Ribeiro Júnior ◽  
Aline Marangon de Oliveira ◽  
Fernando Godoi Silva ◽  
Lorena Natalino Haber Garcia ◽  
Cátia Maria de Oliveira Lobo ◽  
...  
Keyword(s):  
Shelf Life ◽  
Microbiological Quality ◽  
Raw Milk ◽  
Poor Quality ◽  
Pasteurized Milk ◽  
Microbial Counts ◽  
Legal Standards ◽  
Milk Samples ◽  
Brazilian Standard

The dairy industry strives to produce high quality products with high nutritional value as well as to meet the legal standards for longer shelf life. However, these goals are made unfeasible by the poor quality of raw milk produced in some regions of Brazil. Others Brazilian dairy regions, however, already succeed in producing milk with low microbial counts, such as the municipality of Castro, Paraná state, designated as the ‘Brazilian dairy capital’. In order to evaluate the effect of raw milk quality on microbial counts during the shelf life of pasteurized milk, samples were collected from two dairy regions of Paraná: the northern and Castro region, characterized by milk production with high and low microbiological counts, respectively. Samples were experimentally pasteurized and the total microorganism counts were analyzed for 18 days at 7°C, using the Brazilian standard microbiological count limit for pasteurized milk (8 x 104 CFU/mL) as the end of the shelf life. Low microbiological counts in raw milk (Castro) resulted in significantly lower counts shortly after pasteurization and over the entire shelf life, meeting the pasteurized milk standard for 18 days. The temporal evolution in the counts over 18 days for the milks of high and low microbiological count was similar; however, the disparity between the absolute counts between the regions was significant (p < 0.05). Of the milk samples from northern Paraná, four (44.4%) already had counts higher than that of the legislative limit for pasteurized milk immediately after pasteurization. The others (five) reached the maximum microbiological count limit for pasteurized milk on the 6th day after pasteurization. In contrast, the milk from the Castro region remained below the limit throughout the analysis period. Thus, it can be stated that the microbiological quality of raw milk is directly related to the initial count of microorganisms after pasteurization, and that pasteurized milk produced from raw milk with low microbiological counts complies with the Brazilian legislation for 18 days following thermal processing.

Molecular Analysis of Spoilage-Related Bacteria in Pasteurized Milk during Refrigeration by PCR and Denaturing Gradient Gel Electrophoresis

2009 ◽  
Vol 72 (3) ◽  
pp. 572-577 ◽  
Author(s):  
HONGFEI HE ◽  
JIN DONG ◽  
CHIN NYEAN LEE ◽  
YONG LI
Keyword(s):  
Shelf Life ◽  
Gel Electrophoresis ◽  
Denaturing Gradient Gel Electrophoresis ◽  
Plate Count ◽  
Pasteurized Milk ◽  
Milk Samples ◽  
Gradient Gel Electrophoresis ◽  
Aerobic Plate Count ◽  
Species Specific

Bacterial diversity in fluid milk products has been extensively studied in order to improve milk quality. Here, we illustrate the utility of viable counts and PCR–denaturing gradient gel electrophoresis (DGGE) for monitoring the microbial spoilage of pasteurized milk during shelf life. Five pasteurized milk samples stored at 4°C were examined at 10 and 5 days before expiration and on the expiration day. With bacterial DNA extracted directly from the samples, PCR-DGGE analysis indicated that Pseudomonas became dominant in four samples. Meanwhile, the aerobic plate count of these four samples exceeded the regulatory limit of 20,000 CFU/ml at 5 days before expiration, and the rapid psychrotrophic count markedly surpassed the aerobic plate count on the expiration day. Streptococcus and Buttiauxella spp. were detected in several samples. Sequence analysis of DGGE fragments revealed high diversity among Pseudomonas spp. in the milk samples. P. putida and P. migulae grew to high numbers during refrigerated storage. Further identification of Pseudomonas at the species level was facilitated by PCR and multiplex PCR using species-specific primers; consequently, P. fluorescens and P. fragi were observed. These results highlight an important role of Pseudomonas in the shelf life of pasteurized milk.

scholarly journals Stability of Lactic Acid Bacteria in Pasteurized Cow’s and Goat’s Milk

2019 ◽  
Vol 1 (4) ◽  
pp. 77-82
Author(s):  
Nurfarhana Syed Malik ◽  
Mohd. Nizam Lani ◽  
Fauziah Tufail Ahmad
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Viable Count ◽  
Plate Count ◽  
Pasteurized Milk ◽  
Milk Samples ◽  
Goat’S Milk ◽  
Different Types ◽  
Goat's Milk ◽  
The Stability

This study was done to determine the effect of pasteurization on the stability of lactic acid bacteria (LAB) and its enzyme in raw and pasteurized cow’s and goat’s milk. The total viable count for plate count of the bacterial growth concentration was higher in both pasteurized cow’s and goat’s milk at 2.48 log CFU/ml. This is followed by raw cow’s milk (1.59 log CFU/ml) and raw goat’s milk (0.65 log CFU/ml). Lactic acid bacteria (LAB) was found to be similar in both raw cow’s and goat’s milk (p>0.05), and pasteurized milk of both animals also contained the same amount of LAB (p>0.05). LAB was still detected in pasteurized milk (p<0.05), indicating the stability of LAB against the pasteurization temperature. Interestingly, based on API ZYM assay kit results, there were nine different enzymes detected in all samples, which were leucinearylamidase, valinearylamidase,cystinearylamidase, trypsin, α-chymotrypsin, naphthol-AS-BI-phosphohydrolase, α-glucosidase, β-glucosidaseand acid phosphatise. The results revealed that different types of lactic acid bacteria were detected in treated and non-treated milk samples produced by different animals, indicating the different stability levels of LAB against pasteurization.

Quality evaluation of different types of chicken consumed in Puerto Rico

1969 ◽  
Vol 74 (1) ◽  
pp. 75-81
Author(s):  
Fred Fernández-Coll ◽  
Wanda Molina-Rivera ◽  
Teresa Dopazo-Rodríguez ◽  
Isabel B. De Caloni
Keyword(s):  
Puerto Rico ◽  
Shelf Life ◽  
Quality Evaluation ◽  
Psychrotrophic Bacteria ◽  
General Quality ◽  
Different Types ◽  
General Acceptability

A study was done to compare the general quality, microbiology and shelf-life of fresh and frozen chicken. Two brands of frozen Grade A, one brand of frozen Grade C and one brand of fresh chicken were compared for yield, texture, general acceptability, psychrotrophic bacteria contents after one, two, and three cycles of thawing and freezing, and shelf-life once it was kept at 7.2° C (45° F) after thawing. Unfrozen fresh chicken samples were anlyzed for psychrotrophic bacteria and shelf-life as a control . Results indicated that there are no significant differences (P > 0.05) in yield, texture and general acceptability among the fresh and frozen chickens studied. The size of the psychrotrophic bacteria population is generally not affected by up to three cycles of thawing and freezing. With the exception of the frozen Grade C chickens analyzed, shelf-life was not generally affected by up to three cycles of thawing and freezing as compared with samples that were unfrozen and frozen and thawed only once.

scholarly journals Rapid Impedance Method for Predicting the Potential Shelf Life of Packaged Pasteurized Milk

2003 ◽  
Vol 86 (5) ◽  
pp. 998-1002 ◽  
Author(s):  
Li Zhiyong ◽  
Yi Minying ◽  
Gao Jianting
Keyword(s):  
Shelf Life ◽  
Traditional Method ◽  
Elevated Temperatures ◽  
Impedance Method ◽  
Detection Time ◽  
Pasteurized Milk ◽  
Estimation Process ◽  
Milk Samples ◽  
Colony Forming Units

Abstract The potential shelf life of packaged pasteurized milk was studied using a rapid impedance method. The results showed a high correlation between the shelf life of Fengxing and Xiang Man-lou pasteurized milks and between the detection time and the logarithm of colony-forming units per milliliter. The impedance detection time was measured after preliminary incubation at 30°C for 6 h for 100 and 200 μL milk samples, or at 37°C for 6 h for 100–400 μL milk samples for Fengxing pasteurized milk, and after 6 h preliminary incubation at 30°C for 300 and 400 μL milk samples or6hat37°C for 100–400 μL milk samples for Xiang Man-lou pasteurized milk. Regressive equations were then constructed to predict the potential shelf life. Compared with the traditional method, the impedance method plus pre-incubation of milk at elevated temperatures (30 and 37°C) was rapid, accurate, and convenient. The entire estimation process was completed within 11–14 and 14–20 h for Fengxing and Xiang Man-lou pasteurized milks, respectively.

Heat-Resistant Psychrotrophic Bacteria Isolated from Pasteurized Milk

1977 ◽  
Vol 40 (5) ◽  
pp. 329-329
Author(s):  
C. J. WASHAM ◽  
H. C. OLSON ◽  
E. R. VEDAMUTHU
Keyword(s):  
Pasteurized Milk ◽  
Psychrotrophic Bacteria ◽  
Heat Resistant

scholarly journals Evaluating the shelf-life of pasteurized milk in Oman

Heliyon ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. e06555
Author(s):  
M. Al-Farsi ◽  
I. Al-Gharibi ◽  
A. Al-Abri ◽  
A. Al-Humaimi ◽  
F. Al-Nabhani ◽  
...  
Keyword(s):  
Shelf Life ◽  
Pasteurized Milk

Characterization of Serratia species and qualitative detection of Serratia marcescens in raw and pasteurized milk by an analytical method based on polymerase chain reaction

2021 ◽  
Vol 67 (2) ◽  
pp. 3453-3464
Author(s):  
Evelin Korcz ◽  
László Varga ◽  
Zoltán Kerényi
Keyword(s):  
Serratia Marcescens ◽  
Bacterial Species ◽  
Relevant Literature ◽  
Inhibitory Effect ◽  
Test Methods ◽  
In Vitro Assays ◽  
Pasteurized Milk ◽  
Milk Samples ◽  
Microbiological Methods

Serratia species are opportunistic pathogenic microorganisms primarily known as nosocomial infectious agents, which can also cause food quality problems. The appearance of the extracellular pigment-producing Serratia marcescens in cow’s milk causes its red discoloration, posing a challenge to the dairy industry and food certification laboratories. The detection of the bacterium by conventional procedures based on microbiological methods is time-consuming and labor-intensive, and in many cases does not lead to satisfactory results due to the competitive inhibitory effect of the accompanying microflora. Following the analysis of the relevant literature, the published endpoint PCR methods and the primers used for the detection of S. marcescens were evaluated in in silico and in vitro assays, and then the procedure was tested on farm milk samples. Using the method, a total of 60 raw and pasteurized milk samples were analyzed, more than half of which (i.e., 32) were identified as S. marcescens positive. The significance of our work is mainly represented by the application of the published test methods in food industry practice. Our results highlight to the importance of detecting this bacterial species.

Effect of Light on Vitamin Loss and Shelf Life of Pasteurized Milk Packaged in PET Bottles

2012 ◽  
pp. 21-35
Author(s):  
Michael Kontominas ◽  
Anastasia Badeka ◽  
Nikolaos Pournis ◽  
Ioannis Karabagias
Keyword(s):  
Shelf Life ◽  
Pasteurized Milk ◽  
Pet Bottles ◽  
Effect Of Light
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