MANUFACTURING MILK QUALITY: A RE-EVALUATION

1971 ◽  
Vol 34 (5) ◽  
pp. 249-255 ◽  
Author(s):  
William S. LaGrange
Keyword(s):  
Milk Quality ◽  
Plate Count ◽  
Dairy Farmers ◽  
High Count ◽  
Psychrotrophic Bacteria ◽  
Standard Plate Count ◽  
Processing Plants ◽  
Standard Plate ◽  
Plate Counts ◽  
Microscopic Count

The bacteriological quality of manufacturing-grade milk is very similar to that marketed a decade earlier when bulk tanks first came into general use. Milk grading programs usually relied on reduction tests. These tests indicated that most milk supplies were good quality. Based on the Standard Plate Count, data is presented that show approximately one-third of the samples tested, in 1969–70 and in 1957–59, exhibit counts <200,000/ml. Considerable quantities of milk, received at processing plants have plate counts exceeding 1,000,000/ml. Dairy farmers learned they could substitute cooling for cleaning because psychrotrophic bacteria predominated the microflora of most high count bulk milk. These bacteria do not readily reduce resazurin and methylene blue. Psychrotrophs also tend to grow in clumps preventing an accurate evaluation of milk quality using the Direct Microscopic Count (DMC). USDA uses the DMC to test check manufacturing plant's milk supplies. Laboratories are recognizing the value of plating procedures, including the Plate Loop Count, to determine milk quality. Manufacturing-grade milk must be evaluated with a plating procedure before progress can be made in milk quality improvement. One grade of milk is far from being a reality if present levels of manufacturing-grade milk quality are considered.

Use of Individual, Premoistened, Disposable Wipes in Preparing Cow Teats for Milking and Resultant Raw Milk Quality and Production1

1991 ◽  
Vol 54 (12) ◽  
pp. 957-959 ◽  
Author(s):  
ROBERT W. ADKINSON ◽  
RONALD H. GOUGH ◽  
JEFFREY J. RYAN
Keyword(s):  
Raw Milk ◽  
Milk Quality ◽  
Plate Count ◽  
Coliform Count ◽  
Standard Plate Count ◽  
Standard Plate ◽  
Plate Counts ◽  
Water Nozzle ◽  
Daily Milk Production ◽  
Paper Towels

Two methods of preparing cows for milking were compared. One preparation consisted of wiping each teat clean with individual, premoistened, disposable wipes. This method was compared with washing teats with a hand-held water nozzle and drying with individual paper towels. Two groups of eight Holstein cows each were randomly assigned to the two treatments. Aseptically collected weigh jar milk samples from individual cow milkings were analyzed for standard plate count, preliminary incubation count, laboratory pasteurization count, and coliform count. Pretrial bacterial counts were monitored for 2 d and were used as covariates in statistical analyses. Cows were sampled for 7 d followed by a 2-d rest after which treatments were switched and cows sampled for another week. Method of udder preparation did not affect daily milk production, fat or protein percent. Standard plate counts and preliminary incubation counts were significantly lower for wipe treatment (363 vs 933 CFU/ml and 263 vs 661 CFU/ml). There was no treatment difference for laboratory pasteurization count or coliform count. Raw milk quality as determined by standard plate count and preliminary incubation count was improved by the wipe treatment.

Pyruvate as an Indicator of Quality in Grading Nonfat Dry Milk1

1982 ◽  
Vol 45 (6) ◽  
pp. 561-565 ◽  
Author(s):  
R. T. MARSHALL ◽  
Y. H. LEE ◽  
B. L. O'BRIEN ◽  
W. A. MOATS
Keyword(s):  
Geometric Mean ◽  
Regression Line ◽  
Skim Milk ◽  
Plate Count ◽  
Department Of Agriculture ◽  
Standard Plate Count ◽  
Geometric Average ◽  
Dry Milk ◽  
Standard Plate ◽  
Microscopic Count

Samples of skim milk and nonfat dry milk (NDM) made from it were collected, paired and tested for pyruvate concentration, [P], and Direct Microscopic count (DMC). The skim milk was tested for Standard Plate Count (SPC) and Psychrotrophic Plate Count (PPC). The geometric average DMC of skim milk was more than three times higher than that of the paired NDM samples. However, [P] of NDM was not significantly different from that of the skim milk. Although [P] of skim milk was poorly correlated with SPC and PPC, r = .31 and .26, respectively, it was relatively well correlated with DMC, r = .64. Data were widely dispersed around the regression line when [P] was ≤ 4.0 mg/L. However, [P] increased rapidly when DMCs were > 106/ml. A limit of 10 mg/L of [P] in NDM reconstituted 1:9 was chosen to represent the current U.S. Department of Agriculture Standard for DMC in NDM. This limit failed to classify about 10% of the samples correctly, assuming that each geometric mean DMC was correct. However, the probability that samples meeting the DMC standard would be rejected by the pyruvate test was quite low and the probability was moderate that samples which would be acceptable by the pyruvate test would be rejected by the DMC. For the latter, 28% of the samples having DMCs of ≥ 107/ml contained < 10 mg/L of pyruvate. No sample having ≥ 10 mg/L of pyruvate had a DMC of ≤ 107/ml. Pyruvate concentration in NDM did not change during storage at 5 or 32°C for 90 days.

Preliminary Incubation Count as an Index of Raw Milk Microbiological Quality During Storage

1984 ◽  
Vol 47 (3) ◽  
pp. 206-208 ◽  
Author(s):  
J. J. RYAN ◽  
R. H. GOUGH ◽  
C. H. WHITE
Keyword(s):  
Microbiological Quality ◽  
Storage Period ◽  
Raw Milk ◽  
Plate Count ◽  
Bacterial Counts ◽  
Sample Group ◽  
Psychrotrophic Bacteria ◽  
Standard Plate Count ◽  
Milk Samples ◽  
Standard Plate

During a 5-month period, 200 raw milk samples were collected from two Louisiana milk plants. Standard Plate Count (SPC), Psychrotrophic Bacteria Count (PBC), and Proteolytic Count (PC) of each sample were initially determined, then monitored daily during a 5-d storage period at 2.2°C. As hypothesized, all bacterial counts increased during the storage period. The magnitude of the increase in bacterial numbers during storage was further investigated by dividing the milk samples into bacteriologically acceptable and unacceptable groups based on SPC or Preliminary Incubation (PI) count. An SPC of 1.0 × 105/ml and PI counts of 1.0 × 105/ml, 1.5 × 105/ml, 2.3 × 105/ml, and 3.0 × 105/ml were used to repeatedly dichotomize the 200 raw milk samples into two groups. Median SPC, PBC, and PC for each acceptable and unacceptable group were then calculated. Dichotomization based on PI counts yielded acceptable sample groups having consistently lower bacterial counts during storage than did the acceptable sample group, which resulted from the dichotomization based on a SPC of 1.0 × 105/ml. The results of this study indicated that the PI count is of considerable value for raw milk quality control.

Subpasteurization Heat Treatment to Inactivate Lipase and Control Bacterial Growth in Raw Milk

1982 ◽  
Vol 45 (6) ◽  
pp. 513-515 ◽  
Author(s):  
G. F. SENYK ◽  
R. R. ZALL ◽  
W. F. SHIPE
Keyword(s):  
Heat Treatment ◽  
Lipase Activity ◽  
Raw Milk ◽  
Heat Treatments ◽  
Plate Count ◽  
Psychrotrophic Bacteria ◽  
Standard Plate Count ◽  
Heat Treated ◽  
Standard Plate ◽  
And Control

Raw milk was heat-treated under subpasteurization and suprapasteurization conditions, cooled and stored for up to 72 h at 4.4 and 6.7°C. Milk lipase activity and bacteria counts were monitored in both unheated and heated milks. Inhibition of milk lipase activity ranged from 42 to 98% for treatments of 57.2°C for 10 sec to 73.9°C for 10 sec, respectively. The logs of Standard Plate Count after 72 h of storage at 6.7°C were 6.56, 4.86, 4.31, 4.00 and 2.82 for unheated and 10-sec heat treatments at 57.2, 65.6, 73.9 and 82.2°C, respectively. Psychrotrophic Bacteria Counts were also lower in the heated milks than in the unheated milk. The logs of Psychrotrophic Bacteria Counts after 72 h of storage at 6.7°C were 6.21, 2.45, 2.27, 1.33 and 1.00 for unheated and 10-sec heat treatments at 57.2, 65.6, 73.9 and 82.2°C, respectively. Heat treatment of raw milk supplies would result in limiting action of the milk lipase system and growth of bacteria.

Effect of Delayed Heading on Some Quality Attributes of Penaeus Shrimp1

1979 ◽  
Vol 42 (5) ◽  
pp. 407-409 ◽  
Author(s):  
R. J. ALVAREZ ◽  
J. A. KOBURGER
Keyword(s):  
Panel Data ◽  
Storage Period ◽  
Plate Count ◽  
Sensory Panel ◽  
Bacterial Populations ◽  
Standard Plate Count ◽  
Plate Count Agar ◽  
Pseudomonas Species ◽  
Standard Plate ◽  
Plate Counts

To determine the effect of delayed heading on shrimp quality, shrimp were stored on ice with and without heads for 10 days. Some shrimp were delay-headed after 5 days and returned to ice for the remainder of the storage period. Microbiological studies were conducted at 0, 5 and 10 days of storage. Total aerobic plate counts were done using Standard Plate Count agar with an added 0.5% NaCl. Incubation was at 20 C for 5 days. Analyses indicated similar counts on shrimp tails stored with or without heads and those delayed-headed. Counts ranged from 2.4 × 106 bacteria/gram at 0 day to 1.6 × 109 bacteria/gram on the 10th day. Identification of the flora present revealed that the same major groups of organisms predominated on shrimp tails subjected to the different storage treatments and the head did not alter development of the usual flora. Flavobacterium, Pseudomonas, Planococcus, Moraxella and the Vibrio/Aeromonas group were the major genera encountered. A shift in bacterial populations was observed during storage. Flavobacterium species predominated during the first 5 days of storage; however, after the fifth day Pseudomonas species predominated. Sensory panel data revealed no differences in acceptability between shrimp tails stored with or without heads and those delay-headed.

THE QUALITY OF RAW MILK FROM SELECTED OHIO MARKETS.

1966 ◽  
Vol 29 (4) ◽  
pp. 118-121 ◽  
Author(s):  
S. P. Ohri ◽  
W. L. Slatter
Keyword(s):  
Raw Milk ◽  
Plate Count ◽  
High Count ◽  
Coliform Count ◽  
Standard Plate Count ◽  
Milk Samples ◽  
Bacteriological Method ◽  
Standard Plate ◽  
Bulk Tank

Summary An 8-month survey of the bacteriological quality of bulk tank produced fluid milk supplies for four major markets in Ohio, was made utilizing the Standard Plate Count (SPC), the preliminary incubation count (PI), the thermoduric (pasteurized milk) count, and the coliform count. In terms of maximum standards of 200,000 and 100,000 organisms/ml, the SPC would have eliminated 13% and 20% of the milk samples, respectively. A SPC of 50,000/ml, a PI count of 200,000/ml, a thermoduric count of 500/ml, and a coliform count of 100/ml would have eliminated 37%, 34%, 40%, and 40%, respectively, of the samples but not all of the samples eliminated by one test were eliminated by another test. All of the tests employed showed a seasonal trend especially in the high count categories but the trend was less noticeable in the results of the preliminary incubation count. A combination of two of the methods was superior to any single bacteriological method employed in detecting unsatisfactory milk. Of the tests used, the combination of the thermoduric count (500/ml) and the coliform count (100/ml) was the most effective in the detection of unsatisfactory milk samples.

Biogenic Amine Survey and Organoleptic Changes in Fresh, Stored, and Temperature-Abused Bluefish (Pomatomus saltatrix)

1999 ◽  
Vol 62 (9) ◽  
pp. 1033-1037 ◽  
Author(s):  
TODD M. GINGERICH ◽  
TATIANA LORCA ◽  
GEORGE J. FLICK ◽  
MERLE D. PIERSON ◽  
HAROLD M. McNAIR
Keyword(s):  
High Performance Liquid Chromatography ◽  
Biogenic Amine ◽  
High Performance ◽  
Plate Count ◽  
Pomatomus Saltatrix ◽  
Morganella Morganii ◽  
Standard Plate Count ◽  
Histamine Formation ◽  
Standard Plate ◽  
Plate Counts

Changes in histamine, putrescine, and cadaverine concentrations in bluefish filets (Pomatomus saltatrix) stored at 5, 10, and 15°C were determined using high-performance liquid chromatography. An organoleptic assessment was conducted simultaneously with the biogenic amine analyses. The histamine levels found in fresh bluefish obtained from wholesale seafood distributors ranged between <1 ppm and 99 with an average of 39 ppm. Putrescine and cadaverine were not found in fresh bluefish. Fish fillets stored at each of the three temperatures developed histamine. The greatest accumulation of histamine was observed in fish stored at 15°C, which developed histamine levels as high as 2,200 ppm. Putrescine levels increased at each temperature during storage. Cadaverine was present only in uninoculated bluefish stored at 15°C. Histamine achieved higher levels in bluefish pieces inoculated with Morganella morganii, which demonstrates that bluefish support bacterial histamine formation. Histamine levels at each temperature exceeded the 50-ppm advisory level established by the Food and Drug Administration before 100% sensory rejection. Standard plate counts increased during storage of fish at all temperatures, but the correlation between histamine levels and standard plate count was not significant.

A COMPARISON OF THE EFFECT OF FOUR MILKING MACHINE CLEANING AND SANITIZING PROCEDURES ON THE STANDARD PLATE COUNT OF RAW MILK1

1955 ◽  
Vol 18 (11) ◽  
pp. 284-287
Author(s):  
G. H. Watrous ◽  
E. M. Kesler ◽  
H. V. Atherton
Keyword(s):  
Quaternary Ammonium ◽  
Statistical Difference ◽  
Plate Count ◽  
Standard Plate Count ◽  
Dry Storage ◽  
Standard Plate ◽  
Plate Counts ◽  
Milking Machine ◽  
Water Rinse ◽  
Rack Storage

A study of four milking machine washing and/or sanitizing methods indicates that an adequate washing procedure using the proper alkaline detergent, coupled with dry storage and a warm water rinse before use was as satisfactory as chlorine sanitizing, the use of a quaternary ammonium cleaner sanitizer, or lye rack storage. The plate counts obtained on milk where machines were thus treated showed no statistical difference attributable to the method employed.

Heat Resistant Psychrotrophic Bacteria in Raw Milk and Their Growth at 7 C

1978 ◽  
Vol 41 (2) ◽  
pp. 93-95 ◽  
Author(s):  
E. M. MIKOLAJCIK ◽  
N. T. SIMON
Keyword(s):  
Heat Treatment ◽  
Raw Milk ◽  
Plate Count ◽  
Psychrotrophic Bacteria ◽  
Standard Plate Count ◽  
Heat Resistant ◽  
Heated Milk ◽  
Standard Plate ◽  
Subsequent Storage ◽  
Microbiological Data

Microbiological data are presented for 109 raw milk samples, and for the same samples after heat treatment at 80 C for 12 min, and upon subsequent storage at 7 C for 7, 14, and 28 days. The Standard Plate Count of the raw milk averaged 110,000/ml with 65% of these organisms being penicillin-resistant. Immediately after heat treatment, 87% of the samples had psychrotrophic spore counts< 10/ml. After 14 and 28 days of storage, 50 and 83% of the samples had psychrotrophic counts ≥ 100,000/ml. It was concluded that growth of heat-resistant psychrotrophic organisms may cause spoilage of heated milk. No relationship could be demonstrated between gram-negative counts of raw milk, or initial mesophilic spore counts of heated milk, and bacterial numbers in heated, stored milk.

A COMPARATIVE EVALUATION OF OFFICIAL METHODS FOR THE STANDARD PLATE COUNT OF CREAM

1972 ◽  
Vol 35 (12) ◽  
pp. 730-732
Author(s):  
A. R. Brazis ◽  
J. W. Messer ◽  
J. T. Peeler
Keyword(s):  
Statistical Analysis ◽  
Comparative Evaluation ◽  
Plate Count ◽  
Precise Method ◽  
Standard Plate Count ◽  
Standard Plate ◽  
Plate Counts

Three official methods to measure cream samples for Standard Plate Counts (SPC) were reviewed. A statistical analysis was made of results from 135 analysts over a 2-year period. Results demonstrated that: (a) pipetting samples is the least precise method to prepare cream samples for the SPC, (b) when compared to the SPC variance of 0.012, variation among analysts is significant for the procedure that weighs 11 g of cream, while the among-analyst variance is not significant when the 1-g weighing procedure is employed, and (c) weighing 1 g of cream is the most precise method to prepare cream samples for SPC determinations.

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