Milk Plant Research Articles

Utilization of dairy waste for vitamin B 12 fermentation

Whey samples collected from Composite Milk Plant, Ludhiana (May, 1980 to July, 1981) had high lactose (2·80-6·11%), protein (0·325-0·485%), fat (0·10-0·25%) and lactic acid (0·14-0·40%) contents resulting in a high Biochemical Oxygen Demand (BOD 5 24·8–59·1 × 10 3 mg litre −1). Propionibacterium shermanii 566 synthesized 5·76 mg vitamin B 12 per litre of whey containing 4% lactose supplemented with 0·5% (NH 4) 2HPO 4, when fermentation was carried out at 30°C under anaerobiosis for the first half (84 h) followed by aerobiosis for the second half of the fermentation (84 h). The metabolite started accumulating at the end of the maximum growth phase (4th day) and lasted until the curve reached a plateau (7th day). Growth of P. shermanii 566 also reduced the BOD of the whey by >90%, thereby decreasing the BOD of the milk plant effluents. The vitamin B 12 enriched fermented whey was found to replace the animal protein factor (APF) as a vitamin B 12 source in poultry rations. Therefore, the technology developed is a worthwhile attempt to utilize whey for vitamin B 12 production and, in turn, reduce the water pollution problem.

Pressure drop in milking machine air pipes

The air flow in a large milking plant has been analysed assuming the flow to be in turn incompressible, isothermal and adiabatic. The results obtained were then compared with results from a laboratory rig which was set up to measure the air flow and pressure drop in two sizes of stainless steel pipe. It was found that at the low Mach numbers achieved in air pipes there was no significant difference between the three methods, indicating that the flow could be assumed to be incompressible, which represents the simplest analysis. This was confirmed by the results of tests with the laboratory rig. In a further test the pressure loss due to a 90° bend was measured and found to be equal to the drop in 0·6 m of straight pipe of the same bore.

Influence of Drying Plant Environment on Salmonellae Contamination of Dry Milk Products

This study was done to correlate incidence of salmonellae found in the dry milk processing plant environment with finished product contamination. Three plants with various histories of environmental salmonellae incidence were chosen for the study. The daily plant samples representing one lot of production were placed in a 1500-g composite in a sterile sample container and submitted to the central analytical laboratory for analysis. Two samples of nonfat dry milk were found to contain salmonellae in 8 continuous months of sampling and testing. In each instance of finished product positive, the environment had at least four positive samples recorded in the routine environmental program during the week or on the day in which the positive product was noted. Repeat tests of the positive product were negative on one lot and confirmed the positive in two of three retests of the other lot. It may be concluded from this study that controlling salmonellae in the dry milk plant environment will effectively preclude finished product contamination since dry milks are produced in essentially closed systems in a process that includes a pasteurization step.

Heating and Storing Milk on Dairy Farms Before Pasteurization in Milk Plants

Fresh uncooled raw milk was heated at subpasteurization temperatures through a thin plate heat exchanger and stored in a refrigerated bulk tank at 3±1° C. Equal quantities of heated milk were added to the tank each day or every other day. After 7 days, the stored milk was delivered to a milk processing plant where it was pasteurized. Chemo-biological analysis of the milk before and after pasteurization indicated that the farm-heated milk maintained satisfactory quality after 7 days of storage at 3±1° C. Selected data on the stored milk were comparable to those of regular milk for bacterial counts, acid degree values, and amino acid composition. A consumer panel of 800 persons tasted pasteurized, aged, farmheated (stored) milk, and fresh milk control. About 43% of the panelists expressed no sample preference; 30.8% of the panelists preferred fresh milk.

Optimum Number and Location of Manufacturing Milk Plants to Minimize Marketing Costs

Historically, the manufacturing milk sector has been treated as the residual segment of the dairy industry. Milk for fluid consumption has always had first claim on Grade A milk production and any excess milk has been available for manufactured products. The pricing system for milk reflects the dependence on manufactured products as the residual outlet for excess milk. On-farm quality standards for production are lower for manufacturing milk and thus the farm price is lower. The proportion of whole milk produced as manufacturing grade milk is declining as producers shift to Grade A production. The decline in supply has been accelerated to some extent also by the upgrading of on-farm quality standards in recent years. Many small producers left the industry rather than make the necessary expenditures to upgrade on-farm facilities. In addition, the movement of Grade A milk into the expanding fluid milk markets in the South has resulted in a declining quantity of excess Grade A milk. Consequently, there is excess processing capacity in the manufacturing milk sector.

Energy Use Profile in Concentrated and Powdered Milk Manufacture

Direct energy requirements in a plant (Plant A) producing evaporated and condensed milk were 508 kcal/kg processed while those in a plant (Plant B) producing condensed and dehydrated milk were 544kcal. Thermal energy was the major component accounting for about 82% of the direct energy consumed. Consumption of electricity in the plants was less than in fluid milk plants studied earlier. This was due to the absence of refrigerated storage areas. In Plant A, packaging energy was nearly equal to the thermal energy input; steel cans for evaporated milk contributed 87% of the packaging energy. In Plant B, packaging energy was 11 kcal/kg of milk processed. About 14% of the thermal energy consumed was lost into discarded waste streams and hot equipment surfaces. Heat recovery and insulation techniques can reduce the present losses by about 60%.

Fieldmen: Planning Their Work

Most milk producers, co-op leaders and plant managers feel their field men are doing a good job. The fieldman's basic job is as the milk plant's personal contact with its member producers. The fieldman's basic reasons for contacting member producers include: milk quality. Grade A and Manufacturing Grade milk requirements, flavor control, dairy farm building plans, milking equipment installation, herd health, sales and financial arrangements for purchase of equipment, member relations and dealing with members's problems and complaints. The fieldman also works for his milk plant in procurement of new members, hauler relations, membership meetings, administration and record keeping, and cooperating with sanitarians. Along with the foregoing, fieldmen must maintain proper personal habits in dress, vocabulary, smoking and driving. There have been too few rewards given these industry ambassadors, who must fill the varied roles of troubleshooter, psychologist, sanitation specialist and salesman. In the interest of energy conservation and driving time, a daily plan of farm calls in a given area should be worked out by the fieldman. Most fieldmen can best work out their own plan of work, taking into consideration location of the farm and urgency of calls to be made.

What We Have Learned From Metering Milk

Finding differences between farm tank stick measurements and milk plant meters or scales caused Milk, Inc. to seek a new and faster way to locate inaccuracies. Many dollars had been spent on this kind of equipment without the desired results, because of improper installation, care, and operation. We realized that a meter needed special care by a trained person who did not have other responsibilities to divert his attention, so we developed the system explained in this article.

Studies on the Psychrotrophic Bacteria of Dairy Plant Milk

The conditions of contamination with bacteria grown at 5°C for 10 days, 20°C for 4 days, and 35°C for 2 days incubations of raw milk obtained at 2 dairy plants, were studied on 563 samples. After that, 393 strains isolated at 5°C incubation from raw milk, 302 strains at 20°C and 362 strains at 35°C were identified and were tested their growth abilities at 0°C for 14 days, 5°C for 10 days, 20°C for 4 days, and 35°C for 2 days incubations respectively.The results obtained are summarized as follows:1) Bacterial counts of most of raw milk samples were ranged from the level of 103/ml to 106/ml at 5°C incubation, and, from the level of 104/ml to 106/ml at both 20 and 35°C incubations. The number of samples with bacterial counts more than 106/ml was many at 20°C incubation, without the distinctions of season and milking method. On comparison of bacterial counts of samples from hand-milking and milker-milking, their bacterial counts differed in area and season. But it showed a tendency that the number of samples with bacterial counts more than 106/ml was many in milker-milking.2) Total strains of gram-negative bacilli such as Pseudomonas, coliform bacteria, Flavobacterium etc. occupied 80.8% of all strains isolated at 5°C incubation of raw milk. In strains isolated at 20°C incubation, total strains of gram-negative bacilli such as Flavobacterium, coliform bacteria, Pseudomonas etc. were 69.0%. On the other hand, in strains isolated at 35°C incubation, total strains of cocci consisted of Streptococcus mostly were 55.2%, and gram-negative bacilli were only 30.7%.3) Out of 393 strains isolated at 5°C incubation, all but one were well grown at 20°C in growth-test. One hundred and ninety six strains (64.9%) of 302 strains isolated at 20°C incubation were well grown at 5°C. Ninety five point nine percent of 362 strains isolated at 35°C incubation was well grown at 20°C.4) The method at 20°C for 4 days incubation is supposed as more superior than the one at 35°C for 2 days incubation to estimate the viable bacterial counts including both psychrotrophs and mesophiles in raw milk, especially in raw milk arrived at milk plant.

Ecological Survey on Bacterial Contamination of Bottled Milk

Recently, remarkable progress has been made on the sanitary control of the milk plant, especially in the countermeasure against air microbes, by introducing such equipment as an air-conditioner. Then a survey was conducted to analyze the effect of such progress upon the aspect of bacterial contamination of bottled milk and the environment of the plant. Since a similar survey was carried out in 1964 before such progress was made, the present survey was performed almost under the same conditions as it in 1974. After that, results were compared between the two surveys with the following findings.1) When bottled milk was examined for bacterial contamination, psychrotrophic, mesophilic, or coliform bacteria were not detected from it immediately after bottling. When bottled milk was stored at 37°C for 24 hours or at 6°C for 7 days, the number of its samples showing a bacterial count exceeding 50, 000, or the lowest allowable limit, was much lower in the present survey than in the 1964 survey. The frequency of appearance of milk samples which failed to meet the minimum requirements after storage was higher in summer than in winter.2) When bottled milk samples were stored at 37°C in the winter of 1964, their bacterial flora contained various types of thermolabile bacteria simultaneously with Bacillus organisms. When the same samples were stored at 37°C in the winter of 1974, their bacterial flora was composed exclusively of Bacillus organisms, which were presumed to have withstood pasteurization and disinfection. When the same samples were stored at 37°C in the summer of 1974, their bacterial flora contained thermolabile bacteria in addition to Bacillus organisms.3) The count of falling bacteria and the bacterial count of finished products (after storage) were compared between the line with an air-conditioner introduced and that without such equipment introduced in the same plant conducting UHT pasteurization. As a result, much more satisfactory results were obtained from the former line.

Summaries of Papers in this Issue

World Protein Supplies: New Horizons. R. Gordon Booth and B. J. Smith The Development of Taints in Pasteurized Cream. Margaret M. Taylor The Impact of Intervention Board Operations on the UK Dairy Industry. M. E. Bessey The Changing Breed Structure of Scottish Dairy Cattle. K. R. Robertson Use of Nitric Acid in Reverse‐flow Washing of a 22‐Unit Milking Plant. J. Palmer and J. O'Shea

USE OF NITRIC ACID IN REVERSE‐FLOW WASHING OF A 22‐UNIT MILKING PLANT

Reverse‐flow washing of a 22‐unit pipeline milking plant in a Turnstyle milking parlour was studied during a milking season. The quantity of detergent solution used/wash was 2701 which was preceded and followed by 4401 of rinse water. Two concentrations of nitric acid and surface active agent were used as the cleansing agent in hot and at one concentration in cold water for 5 consecutive 6‐week periods. Bulk milk and cluster rinse samples taken at weekly intervals were tested for total colony and coliform count. It is concluded that nitric acid 0‐3 per cent w/v plus a wetting agent in hot water is an effective detergent system for reverse‐flow washing of large pipeline plants.

A Note on the Intraurban Location of Wholesalers and Local-Market Manufacturers

In their seminal study of spatial economy of New York Metropolitan Region, Hoover and Vernon [1959] argue that industries which ship to local consumers [such as] newspapers, bakeries, breweries, bottling works and milk plants ... have sought out comparatively central locations in in order to minimize both average delivery time, since deliveries must be closely timed at peril of missing sales, and average distance traveled to customers, since the cost of transport must be held to a minimum because of comparatively low value of delivered product [pp. 36, 37]. They note, however, that these industries, though seemingly locked to a central point, since the center of an area, generally speaking, is least-cost point from which distribution can be made,.., .have shown a tendency to move outward in recent years. In case of national-market industries, Hoover and Vernon attributed increasing decentralization to advent of motor vehicle, but they do not do so with local-market industries. Instead they suggest that, one reason for outward shift is that consumers are gradually spreading out from center of Region. Another reason, it is now becoming evident, is that, after all, center of Region is not always least-cost point for distribution, because center is more highly congested than surrounding market areas [1959, p. 37]. At another point in study, Hoover and Vernon argue that congestion in central area is also assumed to be a factor causing decentralization of wholesalers. Wholesalers covering whole Region will find advantages in locating their distribution points outside central nub of congestion, following pattern of bakeries and other local market manufacturers [p. 81]. In this note I demonstrate that

Thermoduric and psychrotrophic organisms on poorly cleansed milking plants and farm bulk milk tanks.

Summary. Poorly cleansed pipeline milking plants gave much higher total and thermoduric colony counts than the internal surfaces of refrigerated farm bulk milk tanks, higher counts being recorded for milking plants after circulation cleaning than after cleansing by the acidified boiling water (ABW) method. Psychrotrophic counts were highest for farm milk tanks and lowest for milking plants cleansed by the ABW method. There was much variation in the proportion of thermoduric and psychrotrophic organisms in the total bacterial content of milking plants determined at 30°, thermodurics being much more prevalent in 21% of the rinses and psychrotrophs in 16%. Both groups formed about equal proportions in 9% of the pipeline rinses. The bacterial content of the farm bulk milk tanks was characterized by many psychrotrophs and few thermodurics.

Measures of Efficiency in Milk Plant Operations

Measures of Efficiency in Milk Plant Operations

THE USE OF INHIBITORY MEDIA TO SCREEN SOUTH DAKOTA BULK TANK MILK FOR STREPTOCOCCUS AGALACTIAE

Edward's medium with red blood cells, staphylococcus beta toxin, and ferric citrate (TKT medium) was used to culture 4189 bulk tank milk samples from herds supplying seven dairy plants in South Dakota. Identity of organisms with characteristics of Streptococcus agalactiae on TKT was tested by biochemical means. The incidence of S. agalactiae infected herds supplying the seven milk plants ranged from 0% to 66.6% and averaged 4.03%.Difficulty was encountered in identifying S. agalactiae by its characteristics on TKT alone so that only about one out of ten colonies picked as S. agalactiae from TKT had all the characteristics of this organism. Some limitation of the method for use in S. agalactiae eradication is thus indicated. Modified KF Agar was found unsuitable for the direct isolation and identification of S. agalactiae from bulk tank milk.

Bacteriological studies on bulk milk collection: pipeline milking plants and bulk milk tanks as sources of bacterial contamination of milk--a review.

Bacteriological studies on bulk milk collection: pipeline milking plants and bulk milk tanks as sources of bacterial contamination of milk--a review.

Is Fat-Corrected Milk Sufficient?

Since milk plant administrators are investigating protein as a milk accounting and pricing variable, a study determined whether the fat content of milk and dairy products with the weight, were sound criteria for estimating their respective values in the market place. Clearly the fat content and weight of milks and milk products failed to describe their respective wholesale prices.An alternative approach for evaluating milk from lactating dairy cows is suggested. This approach reduces milk equivalents, based on protein and fat contents, to dollars for a hypothetical milk arbitrarily valued at $5 per hundredweight. Several advantages inherent in the suggested milk evaluation system are discussed including benefits which could accrue to milk producers and milk consumers. Milk processors could also benefit because of an improved accounting system which may prove to have extensive effects upon the present price structure in marketing milk and milk products.

Economic Incentives for Cheese Processors Using a Protein-Fat Milk Pricing Model

A case study projecting the monetary inlpact on a hypothetical cheese plant changing from fat-hundredweight producer payment to a protein-fat pricing plan was investigated. The hypothetical cheese plant is situated in an area which produces 2,185,000 pounds of milk daily. This plant received 437,000 pounds of milk daily beforé adopting the novel protein-fat payment plan.Milk supplies originating from 746 herds in Utah, 333 herds in North Dakota, 103 herds in Wisconsin, and 239 individual cow milk samples were statistically analyzed by simple and weighted linear regression models. Monetary projections, given specific assumptions, were used for the Utah milk to evaluate the relative position of the Inilk plant introducing the protein-fat pricing system as compared to competitive plants pricing milk by orthodox fathundredweight payments.The annual economic incentive generated by the protein-fat pricing plan was $2,077,581 per year. The annual economic incentive differential between the hypothetical plant and the competing milk plants was $4,155,162.

MANUFACTURING MILK QUALITY: A RE-EVALUATION

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.