Acid Degree Value Research Articles

Factors Affecting Lipase Flavor in Butter

In studies to determine the effect of cream quality, pasteurization temperature, and storage temperature on the development of lipase flavor in butter, raw cream, fresh and aged 24h, was divided into three fractions and heated at 72C, 85C, and 93C, respectively, for 18s. Each fraction of cream was churned into butter, which was divided and stored at −28.9C and 4.4C. Lipase flavor development was measured organoleptically, by acid degree value, and by free fatty acid concentration. Age of the cream significantly affected free fatty acid and acid degree values whereas heat treatment of the cream affected free fatty acids, acid degree values and flavor, and the temperature of storage affected free fatty acids and flavor. Correlation between free fatty acids and acid degree values was .86. There was no correlation between flavor and either free fatty acids or acid degree values.

An Evaluation of Methods for Detecting and Comparative Incidence of Penicillin Residues in Different Types of Raw Milk Supplies

Over a one-month period, 288 samples of raw milk (equally divided among grade A, and manufacturing grade can and bulk milk producers) were tested by the disc assay and Delvotest P methods for penicillin residues. All positive samples were also checked by the Sarcina lutea cylinder plate method. The disc assay procedure detected one positive sample (0.34%), the Delvotest P method seven positive samples (2.4%) and one questionable (+/−) reaction. When applied to samples found positive by the Delvotest P procedure, the cylinder plate method identified as positive two samples. The Delvotest P method was found sensitive to 0.002 unit of penicillin. Hydrolytic rancidity (to acid degree values as high as 4.75) caused no false positive reactions. When applied to delactosed whey, false positive reactions did occur, as has been noted with other methods.

Influence of Mastitis on Properties of Milk. X. Fatty Acid Composition

The effect of mastitis on the concentration of fatty acids in individual quarter milk samples was investigated. Wisconsin Mastitis Test positive (>20mm) milks contained higher Lipase activities and acid degree values and lower concentrations of phospholipids than the corresponding negative (<10mm) milks. Positive milks contained higher concentrations of free fatty acids and short chain (4 to 12 carbons) fatty acids, and lower concentrations of the long chain (16 and 18 carbons) fatty acids. Total fatty acid content of the positive milks was approximately 4% lower while the free fatty acid content was approximately 47% higher than for the negative milks. Increases in the concentrations of individual free fatty acids ranged from approximately 5 to 80%.

Simple Test for Milk Lipolysis and Changes in Rancidity in Refrigerated Pasteurized Milk

The Rhodamine 6G method for determining fatty acids of Chakrabarty et al. (J. Amer. Oil Chem. Soc., 46:473. 1969) was modified for quick detection of lipolysis in milk. Two milliliters of milk are extracted with 5ml of benzenc, A ml of 30% potasium oxalate and one drop of phosphoric acid. Two milliliters of the filtered extract are mixed with 1ml of Rhodamine 6G in benzene and the color is compared with a standard prepared by mixing lauric acid with Rhodamine 6G. This method is simpler than the previous Rhodamine B method. (J. Dairy Sci., 53:537. 1970) as evaporation of solvents is unneccessary.The acid degree values in commercial pasteurized milks increased by .3 to .6 during refrigerated storage for seven days. A relationship was observed between the acid degree values and the bacterial counts after 7-day storage.

FLAVOR CHARACTERISTICS OF NORMAL AND ABNORMAL MILK

Flavor is one characteristic of quality in raw milk. Presence of abnormality, as reflected in somatic cell levels, is considered aesthetically undesirable and may well affect the flavor characteristics of raw milk. Raw milk producer samples were analyzed for flavor, somatic cell concentration, acid degree value, total and coliform bacteria, pH, butterfat, and total solids. There was an inverse relationship between flavor score and acid degree value. Results did not confirm the supposition that somatic cell concentrations may affect the flavor of raw milk.

EFFECT OF THE COW'S BODY CONDITION AND STAGE OF LACTATION ON DEVELOPMENT OF MILK RANCIDITY

An objective of this study was to investigate the relationship between body condition of the dairy cow and susceptibility of milk to rancidity. Initial milk samples were obtained from 166 cows in Spring, 1969, and all animals were retested after an interval of two months. Additional observations included the effects of stage of lactation, level of milk production, and herd effects. Each cow was evaluated for body condition, at the times when milk samples were obtained, by a method based on measures of weight and skeletal size and by a subjective scoring system. Spontaneous rancidity of the milk fat was allowed to develop upon storage for 48 hr; and induced rancidity was brought about by controlled agitation. As measured by acid degree values (ADV) the treatments imposed on the milk samples were successful in simulating development of spontaneous and induced lipolysis of the milk fat. However, the magnitude of the ADV was not related to body condition score. It is concluded that in well-fed herds, such as those used in this experiment, body condition of the cow does not influence the susceptibility of her milk to rancidity. These data may not apply under conditions of poor feeding and management. Advancing stage of lactation was associated with increases in both spontaneous and induced rancidity. This was indicated by positive correlations between days in milk and ADV, and by significantly higher values in the second sampling period than in the first. There was a negative correlation between the amount of milk produced and ADV. This may have been related to the decline in milk flow which accompanied advancing lactation. An unexplained herd difference existed with respect to the susceptibility of milk to induced rancidity.

Simple Test for Lipolytic Rancidity in Milk

The Rhodamine B method of MacKenzie et al. (2) was simplified for determining lipolytic rancidity in milk. This may facilitate detection of rancid milk and prevent intermixing with normal milk. Lipids extracted from 2ml of milk with petroleum ether were dried, dissolved in toluene and color produced by shaking with Rhodamine B was compared with a color disc in a portable comparator. This method compared with acid degree values revealed a highly significant correlation coefficient of 0.924 for 23 milks, acid degree values of from 0.6 to 2.0, out of 40 different milks; the other 17 milks were so rancid they exceeded the comparator's color range. Detection of above 1.2 acid degree values is possible by this method. Hydrogen peroxide and sodium tetraphosphate were effective in preventing activation of the milk lipase system by agitation.

Influence of Mastitis on Properties of Milk. IV. Hydrolytic Rancidity

The effect of mastitis on acid degree values and lipase activity of milk was investigated using quarter milk samples obtained from individual cows. Both acid degree values and lipase activity were significantly higher (P<0.01) in the Wisconsin Mastitis positive (>20mm) samples than in the corresponding negative samples (<10mm). Initial acid degree values for the mastitis positive (>20mm) samples were 35 to 40% higher than for the negative samples. This relationship was also observed when lipolysis was spontaneous or induced. Lipase activity of the positive samples was approximately 7% higher than for the negative samples.

Chemical and Flavor Changes in Sterile Concentrated Milk During Storage

Three lots of concentrated milk (ultra-high temperature, high-temperature short-time, and conventionally sterilized) were stored at 4, 20, and 37C for eight months, and examined monthly for changes in flavor, volatile compounds as detected by GLC, acid degree values, and severity of browning. One lot of sterile concentrated skimmilk also stored at 4, 20, and 37C was analyzed occasionally during the eight months.Flavor deterioration was rapid at 20 and 37C, with cooked, scorched, and stale flavor defects most apparent. The ultra-high temperature milk had a flavor advantage initially, but after storage flavor scores for all processed milks were at similar levels. Some methyl ketones, furan, and methyl furan increased during storage at 20 and 37C. Milk fat was the precursor of 2-heptanone and 2-pentanone. Increases in acetone, butanone, acetaldehyde, furan, and methyl furan concentration during storage appeared to come from the nonfat portion of milk. Methyl sulfide was derived from the serum phase, but did not increase in concentration during storage. Methyl sulfide was the only volatile compound found at concentrations greater than its threshold value in milk. Acid degree values were high in all freshly sterilized milks and increased slightly at 20C and rapidly at 37C. Browning reaction values increased at 37C storage.

A modification of the acid degree value test for lipolytic rancidity in milk

SummaryWhile using an acid degree value test during work on lipolysis in milk, difficulty was encountered in extracting the fat from the milk of certain cows, especially milk of high butterfat content and milk from newly calved cows. This difficulty was overcome by increasing the quantity of reagent used. A study was made of the quantities of reagent required for milks of different butterfat content and for colostrum. No effect on the acid degree value occurred as a result of increasing the quantity of reagent. A modification of the test is recommended, using an increased quantity of reagent.

EFFECT OF A HIGH-LEVEL AND A LOW-LEVEL MILK PIPELINE ON MILK FAT ACID DEGREE VALUES

SummaryDairy farm milk pipelines located 2 ft below normal udder level and 4 ft above, respectively, were used to determine the effect of milk pipeline height on induced lipolysis. Three trials involving 86 cows and 54 observations were made. The combined data from the three groups, when averaged, indicated mean spontaneous Acid Degree Value increases above mean initial values of 0.68 for the low line and 1.16 for the high line. These results were highly significant (P <0.01) with milk handled through the high line showing a mean ADV increase of 0.48 more than the low line.

Action of Lipases of Staphylococcus aureus on Milk Fat

The activity of the lipase(s) of two strains of coagulase-positive Staphylococcus aureus was determined in milk fat incubated at 15, 22, and 30 C for 8 days. Total fat hydrolysis was measured by acid degree values (ADV). Neutral lipids were separated into component groups on a Florisil column. Free fatty acids were determined by temperature-programmed gas-liquid chromatography. The ADV were 25 to 50% greater at 22 than at 15 C and 4 to 7 times greater at 30 than at 22 C. The lipases liberated as much as 0.48 g of fatty acids per gram of fat during 8 days at 30 C. The enzyme showed a predilection for the palmitic acid-glycerol bond. Addition of fatty acids C 14 to C 18 inclusive to inoculated sterile skim milk caused inhibition of S. aureus as follows: (i) complete at 0.05 and 0.10% concentration of C 10 and (ii) partial at 0.05 and complete at 0.10% concentration of C 8 . The samples showing inhibition were negative for peptonization, coagulase, and change in p H. Addition of oleic and stearic acid to sterile skim milk inoculated with S. aureus resulted in an increase in nonprotein nitrogen, and the C 4 to C 12 acids caused a decrease in protease activity.

Action of Lipases of Staphylococcus aureus on Milk Fat1

The activity of the lipase(s) of two strains of coagulase-positive Staphylococcus aureus was determined in milk fat incubated at 15, 22, and 30 C for 8 days. Total fat hydrolysis was measured by acid degree values (ADV). Neutral lipids were separated into component groups on a Florisil column. Free fatty acids were determined by temperature-programmed gas-liquid chromatography. The ADV were 25 to 50% greater at 22 than at 15 C and 4 to 7 times greater at 30 than at 22 C. The lipases liberated as much as 0.48 g of fatty acids per gram of fat during 8 days at 30 C. The enzyme showed a predilection for the palmitic acid-glycerol bond. Addition of fatty acids C(14) to C(18) inclusive to inoculated sterile skim milk caused inhibition of S. aureus as follows: (i) complete at 0.05 and 0.10% concentration of C(10) and (ii) partial at 0.05 and complete at 0.10% concentration of C(8). The samples showing inhibition were negative for peptonization, coagulase, and change in pH. Addition of oleic and stearic acid to sterile skim milk inoculated with S. aureus resulted in an increase in nonprotein nitrogen, and the C(4) to C(12) acids caused a decrease in protease activity.

Spontaneous and Induced Lipolysis in Milk During Alternate Feeding of Two Winter Rations and of a Winter Ration and Pasture

Summary The milk from ten Holsteins was analyzed for initial acid degree value (ADV), spontaneous lipolysis, and induced lipolysis during a 3-mo. switch-back feeding trial involving two winter rations and a 10-wk. cross-over feeding trial involving a winter ration and pasture. Samples were obtained once a week from each cow. ADVs were determined by the silica-gel method. The different feeding regimes had no significant comparative influence on the incidence of induced lipolysis or the initial ADV. There was no significant difference in the incidence of spontaneous lipolysis between the two winter rations (grain, corn silage, and alfalfa hay versus grain, corn silage, and beet pulp). The feeding of pasture, beet pulp, and grain significantly reduced the occurrence of spontaneous lipolysis over that observed for alfalfa hay, beet pulp, and grain.

Spontaneous Lipolysis in Milk Throughout the Stages of Lactation of Individual Cows

Summary The milk from each of four cows maintained under controlled conditions was checked for spontaneous lipolysis four times a week during a complete lactation by the silica gel method. The average acid degree values (ADVs) were: Cow 1—0.57, Cows 2—0.75, Cows 3—1.25, and Cow 4—1.28. The ADVs increased as lactation progressed with Cows 2, 3, and 4. Samples that were rancid organoleptically were produced only by Cows 3 and 4. Most of these samples were taken during the last month of lactation. There was considerable week-to-week and cow-to-cow variation. The average p.m. ADVs of Cows 2 and 3 were significantly higher than the average a.m. ADVs.

Use of Annatto for Coloring Butter

Summary A comparison was made of the effect of annatto and coal-tar color on the chemical quality of stored butter. Commercial conditions were duplicated by selecting two levels of cream quality, two levels of copper, and two storage treatments. Flavor was evaluated by official graders and by a panel of 15 persons. The surface color was determined with a photoelectric reflection meter and also with Dyeco color standards. Peroxide values were determined by the ferric thiocyanate method; aldehyde values by the rosaniline method; acid degrees by titration; copper content by the carbamate method, and vitamin A by the Carr-Price method. Official graders and a taste panel agreed on a difference in flavor between highand low-copper samples. The flavor of the high-copper samples decreased on storage. No flavor difference was attributable to the type of color. Peroxide and aldehyde values increased on storage in the samples with high copper content, but the type of coloring agent was not a factor. Acid-degree values increased slightly on storage, but were not affected by the type of color or by the level of copper. Carotene accounted for 10% of the vitamin A potency of the butter; it was not affected by storage for 6 mo. at −5° F., but decreased following additional storage for 2 wk. at 60° F. The preformed vitamin A content of the butter was not affected by the type of color, copper level, or storage.

THE ACID DEGREE OF MILK OBTAINED WITH PIPELINE AND BUCKET MILKERS

Pipeline milking as compared to bucket milking increased the magnitude of the acid degree values (silica gel method) of milk samples. Passage of the milk through a diaphram pump further increased the acid degree values in some cases.

THE INFLUENCE OF THE MAXIMUM TEMPERATURE RISE IN BULK TANKS ON MILK QUALITY

On adding warm morning milk to cold evening milk no development of rancidity was detectable with blend temperatures of 40°F., 50°F., and 60°F., but was apparent at a maximum rise of 70°F. Under conditions simulating every-other-day pick-up no significant increase in rancidity occured on raising the blend temperature to 60°F., but a measureable increase did occur with a blend temperature of 70°F. The increment in acid degree values between 24 and 48 hours is much less with every-other-day pick-up than with samples picked up daily.

THE EFFECT OF VARIOUS PIPELINE MILKING CONDITIONS ON THE ACID DEGREE AND FLAVOR SCORE OF MILK

Statistical analyses of acid degree values (Thomas et al.) and rancid flavor scores of pipeline milk subjected to various riser heights and pumping treatments showed that significantly higher acid degree values and poorer flavor scores were associated with risers and with continuous pumping as compared with no risers and intermittent pumping treatments. Milk exhibiting acid degree values of 1.5 or less were consistently judged to be free from rancid flavor.

The Use of Synthetic β-Carotene for Coloring Butter

Summary Synthetic β -carotene was compared with coal-tar as a coloring agent for butter. With a view to duplicating commercial conditions, the comparison was made at two levels of cream quality, two levels of copper and at three periods of storage. Neither official graders nor a taste panel could detect any flavor difference between the two types of butter. Acid degree, peroxide, and aldehyde values were the same for both types of butter, although copper and storage increased the degree of oxidation. Standardizing the color of butter with 0.35g. of synthetic β -carotene per 100lb. of fat gave a slightly deeper color than with 1oz. of coal-tar color per 100lb. of fat. The color intensity of the butter did not change during storage. The average vitamin A potency of the butter was increased 3800 I.U. per lb. as a result of coloring the butter with synthetic β -carotene, and was not affected by storage.