Effect of psychrotrophic post-pasteurization contamination on the keeping quality at 11 and 5 °C of HTST-pasteurized milk in the UK

1982 ◽  
Vol 49 (4) ◽  
pp. 619-630 ◽  
Author(s):  
Monika J. A. Schröder ◽  
Christina M. Cousins ◽  
Charles H. McKinnon
Keyword(s):  
Shelf Life ◽  
Storage Temperature ◽  
Bacterial Counts ◽  
Pasteurized Milk ◽  
Colony Forming Units ◽  
Keeping Quality ◽  
The Uk ◽  
Spoilage Microflora

SummaryThe keeping quality of commercial HTST-pasteurized milk and laboratory pasteurized milk from a common bulk raw supply has been investigated for 5 dairies. Spoilage occurred at levels of total bacterial counts around 107 colony forming units/ml, but with a slightly higher off-flavour threshold for the commercial milks than the laboratory pasteurized milks. The predominant microflora at spoilage and the type of off-flavour produced differed between the 2 types of milk. Raising the storage temperature from 5 to 11 °C caused a slight shift in the spoilage microflora and led to an average reduction in the shelf life of the laboratory pasteurized milk from 28 to 6 d and of the commercial pasteurized milk from 13 to 5 d. Changes in the level of post-pasteurization contamination (PPC) were reflected in changes in keeping quality, particularly at 5 °C. However, the greatest improvements were found in the absence of PPC.

A Membrane-Filter Technique to Test for the Significance of Sublethally Injured Bacteria in Retail Pasteurized Milk

1975 ◽  
Vol 38 (2) ◽  
pp. 87-88 ◽  
Author(s):  
T. J. CLAYDON
Keyword(s):  
Shelf Life ◽  
Membrane Filter ◽  
Selective Medium ◽  
Pasteurized Milk ◽  
Filter Technique ◽  
Litmus Milk ◽  
Keeping Quality ◽  
Membrane Transfer

A membrane transfer procedure previously described was used to study the possible role of sublethally injured bacteria in the keeping quality of retail pasteurized milk. Trypticase soy broth (TSB) was used as nonselective medium and TSB plus NaCl at pH 6.0 (TSBS 6.0), as the selective medium inhibitory to injured organisms. In pasteurized milk at early stages of storage, colony counts on the latter medium were much lower than on the former. Subsequent transfer of the TSBS 6.0 filters to fresh TSB and further incubation usually increased the counts to about the initial TSB range. Generally the organisms presumed injured and subsequently recovered were the same types as those considered uninjured. They were mainly streptococci and micrococci that produced only slow changes in litmus milk at 5 C, so they are of doubtful significance in the shelf life of retail milk at refrigerator temperatures.

Effect of oxygen on the keeping quality of milk: II. Effect of available oxygen on bacterial spoilage and oxygen uptake

1982 ◽  
Vol 49 (3) ◽  
pp. 425-437 ◽  
Author(s):  
Monika J. A. Schröder
Keyword(s):  
Oxygen Uptake ◽  
Shelf Life ◽  
Bacterial Growth ◽  
Bacterial Count ◽  
Bacterial Activity ◽  
Pasteurized Milk ◽  
Keeping Quality ◽  
Quality Of Milk ◽  
Effect Of Oxygen

SUMMARYThe effect of limiting the amount of O2 present in commercially pasteurized milk on bacterial growth and on the keeping quality of the milk was investigated. No increase in bacterial count of laboratory pasteurized milk during storage for 9 d at 5 °C was observed and O2 consumption due to bacterial activity was low. In commercial pasteurized milk containing post-pasteurization contamination (PPC) growth of strict aerobes was encouraged by high O2 content while that of coliforms was less dependent on O2 level. The amounts of headspace (HS) O2 consumed in milk with PPC growth were large. Reducing the dissolved O2 content of commercial pasteurized milk stored in O2-impermeable containers without HS had little effect on bacterial activity and shelf-life.

scholarly journals THE KEEPING QUALITY OF THE PASTEURIZED MILK PRODUCED IN THESSALONIKI - GREECE

1973 ◽  
Vol 24 (2) ◽  
pp. 87
Author(s):  
Α. ΠΑΝΕΤΣΟΣ ◽  
Π. ΚΑΡΑΙΩΑΝΝΟΓΛΟΥ ◽  
Α. ΜΑΝΤΗΣ
Keyword(s):  
Bacterial Counts ◽  
Pasteurized Milk ◽  
Keeping Quality

The keeping quality of the pasteurized milk produced in the district of Thessaloniki was examined. It was found that pasteurized milk which was stored at 4° C, continued to have the same bacterial counts, low acidity, and no off flavours after 48 hours. The results were compared with those obtained from samples of milk collected from different stores.

Usefulness of the Benzalkon-Crystal Violet-ATP Method for Predicting the Keeping Quality of Pasteurized Milk

1982 ◽  
Vol 45 (10) ◽  
pp. 928-931 ◽  
Author(s):  
G. M. WAES ◽  
R. G. BOSSUYT
Keyword(s):  
Shelf Life ◽  
Crystal Violet ◽  
Quantitative Estimation ◽  
Bacterial Count ◽  
Total Bacterial Count ◽  
Life Test ◽  
Pasteurized Milk ◽  
Keeping Quality ◽  
Factory Laboratory

Using the benzalkon-crystal violet-ATP method (BC-ATP method), post-pasteurization contamination of pasteurized milk caused by gram-negative bacteria can be determined within 24 h. This study determined to what extent the keeping quality of pasteurized milk can be predicted by applying this BC-ATP method. Results obtained with the BC-ATP method for 100 samples of pasteurized milk were compared with those recorded in the shelf-life test (total bacterial count after 10 d of storage of samples at 7°C; standard: 106 bacteria per ml) and the Moseley test (bacterial count after 5 d of storage at 7°C; standard: 105 bacteria per ml). Using the shelf life test and the Moseley test, 14 and 8% of the results, respectively, did not correspond with those obtained with the BC-ATP method. From the results obtained, it was obvious that the greater the post-pasteurization contamination of the pasteurized milk, the lesser is the keeping quality. A quantitative estimation of the degree of post-pasteurization contamination can be obtained satisfactorily by applying the BC-ATP method to 1000-, 100-, 10- and 1-ml portions. The Moseley test takes too much time to achieve a good coordination between the factory laboratory and the pasteurization and filling sections of the dairy factory. By substituting the BC-ATP method applied to 100-ml portions of pasteurized milk for the Moseley test (5 d at 7°C; standard: 100,000 bacteria per ml) almost the same information is obtained within 24 h.

THE KEEPING QUALITY OF PASTEURIZED MILK AS INFLUENCED BY THE GROWTH OF PSYCHROPHILIC BACTERIA AND THE ADDITION OF AUREOMYCIN*

1953 ◽  
Vol 16 (5) ◽  
pp. 213-219 ◽  
Author(s):  
J. C. Olson ◽  
D. S. Willoughby ◽  
E. L. Thomas ◽  
H. A. Morris
Keyword(s):  
Storage Life ◽  
Psychrophilic Bacteria ◽  
Bacterial Counts ◽  
Pasteurized Milk ◽  
Complete Destruction ◽  
Reliable Indication ◽  
Keeping Quality ◽  
Long Storage

In studies of the keeping quality of pasteurized milk, it was found that past records from milk plants showing good bacterial counts of finished products, afforded a rather reliable indication that milk from such plants may show better keeping quality than milk from plants with poor past records. Proper pasteurization resulted in extensive if not complete destruction of psychrophiles. Negative coliform counts of freshly pasteurized milk were not reliable as indicators of good keeping quality during storage at the temperature used in these studies. The mere absence of psychrophiles in one or two milliliters of milk was not found to be a guarantee of long storage life. The presence of aureomycin in the concentration used in these studies had no effect in extending the keeping quality of pasteurized milk.

scholarly journals Estimation storage life of blueberry fruits of different taxons

2021 ◽  
Vol 66 (3) ◽  
pp. 302-311
Author(s):  
N. B. Pavlovskiy
Keyword(s):  
Shelf Life ◽  
Storage Temperature ◽  
Storage Life ◽  
Functional Disorders ◽  
Loss Of Weight ◽  
Gas Atmosphere ◽  
Early Maturing ◽  
Keeping Quality ◽  
Taxonomic Affiliation

Based on the results of 12-year studies, the taxonomic characteristics of the keeping quality of berries of 27 cultivars end species of blueberries introduced in Belarus are shown. It was found that the storage postharvest of blueberry fruits under conditions of an ordinary gas atmosphere, depending on the taxon, varied from 7 days (swamp blueberry) to 29 days (‘Darrow' blueberry) at a storage temperature of +5 °C. Among the studied blueberry species, the fruits of tall blueberries and varieties obtained on the basis of this taxon retained their commercial qualities for a much longer period of time, compared to berries of other blueberry species. Fruits of late-ripening tall blueberry cultivars lose weight more slowly during storage and, accordingly, have a longer shelf life compared to berries of early-maturing taxa. The fruits of large-fruited blueberry cultivars are stored longer than the berries of small-fruited taxa of this crop. The keeping quality of blueberry berries, regardless of their taxonomic affiliation, was determined mainly by the natural loss of weight and, to a lesser extent, by waste from functional disorders and rot.

Keeping Quality of Pacific Coast Dogfish

1959 ◽  
Vol 16 (6) ◽  
pp. 791-794 ◽  
Author(s):  
R. H. Moyer ◽  
B. A. Southcott ◽  
E. G. Baker ◽  
H. L. A. Tarr
Keyword(s):  
Pacific Coast ◽  
Sea Water ◽  
Total Volatile ◽  
Bacterial Counts ◽  
Ph Values ◽  
Appreciable Increase ◽  
Muscle Ph ◽  
Keeping Quality ◽  
Viable Bacteria

Pacific coast dogfish (Squalus suckleyi) were held 21 days in ice and in refrigerated sea water with and without added chlortetracycline, viable bacterial counts and volatile bases being determined periodically. Viable bacteria increased sharply after about 14 days but the muscle pH values showed little or no increase. No appreciable increase in the total volatile base or trimethylamine content of the muscle was noted until the fish were stored for more than 2 weeks, and then the increases observed were comparatively small.

Effects of Dry Ice and Superchilling on Quality and Shelf Life of Arctic Charr (Salvelinus alpinus) Fillets

2007 ◽  
Vol 3 (3) ◽  
Author(s):  
Huynh Nguyen Duy Bao ◽  
Sigurjón Arason ◽  
Kristín Anna Þórarinsdóttir
Keyword(s):  
Shelf Life ◽  
Storage Temperature ◽  
Salvelinus Alpinus ◽  
Arctic Charr ◽  
Negative Effects ◽  
Dry Ice ◽  
Fish Flesh ◽  
Microbial Analysis ◽  
And Storage

The influence of different cooling techniques (dry ice/ice packs) and storage temperature (-2°C/3°C) to prolong the shelf life of Arctic charr (Salvelinus alpinus) fillets were evaluated by sensory analysis, physical methods, chemical and microbial analysis. The effects of storage temperature were stronger than of different cooling agents. Superchilling (-2°C) of fillets packed with dry ice resulted in 6 days extension of shelf life compared to chilling (3°C). The use of dry ice parallel to superchilling prolonged shelf life for 1 day compared to fillets stored with ice packs. No negative effects on quality of the fillets where detected that could be linked to cell destruction caused by partial freezing or to sour taste, caused by absorption of CO2 gas in fish flesh.

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