The stomach is an important part of the digestive system.
LINN Milk composition is economically important to milk producers and processors and nutritionally important to consumers.
It has been known for years that variations in milk composition occur; however, the composition of milk marketed nationally has been rather constant over the last 15 years, averaging 3. This is probably partly because of the prominence of the Holstein breed and the pricing of milk based on fat concentration.
The introduction of milk pricing on a component basis and the perception by consumers that animal fats are unhealthy have created new interest in how milk components can be altered to accommodate these emerging markets.
The paper starts with a brief overview of the biosynthesis of milk components since changes in these reflect changes in the mammary gland synthesis or secretion of the component. Factors affecting milk composition such as breed, genetic variation within breed, health, environment, management practices, and diet are then reviewed.
Lipids Biosynthesis The synthesis of milk fat has been recently reviewed Dils,; Larson, ; Book and Thomas, The following discussion highlights relevant stages of biosynthesis where fat composition can be altered.
The predominant fat in milk is triacylglycerol, which contains fatty acids of short- C4-C10intermediate- CC16or long-chain C18 length. The short-chain acids are synthesized within the mammary.
In broad terms, about 50 percent of the fatty acids in milk are synthesized in the mammary gland and the other 50 percent are derived directly from blood. Fatty acids are synthesized in the mammary gland via the malonyl coenzyme A malonyl-CoA pathway.
Blood beta-hydroxybutyrate is primarily used for the first four carbons initiating fatty acid synthesis. Chain length occurs two carbons at a time, with acetate being the major carbon donor.
Once formed, fatty acyl-CoAs may combine with glycerol or diacylglycerol or monoacylglycerol to form triacylglycerol. Placement of the fatty acids on the glycerol molecule is not random.
Short-chain fatty acids are essentially in the 3 position, and C18 acids are on either the 1 or 3 position. Triacylglycerols are synthesized in the endoplasmic reticulum. As they are formed, they are rapidly incorporated into lipid-covered droplets.
The droplets then migrate toward the apical membrane of the secretory cell, where they become encapsulated by the membrane, pinched off, and released into the lumen. Gaunt reported cattle in the United States tend to have the lowest percentage of milk fat. This may be partly because of environmental factors, but some genetic variation within a breed in different countries must exist.
The repeatability from one lactation to another for the percentage of constituents in milk is quite high, an average of 0. Repeatability of milk fat percentage for Holsteins is 0. Other breeds appear to have a similar repeatability. Jerseys have the highest heritability for milk fat percentage 0.
The small variation between ratios of one milk constituent to another, particularly fat to protein, suggests little hope for drastic changes in milk yield and milk composition Gaunt, ; Wilcox, Differences in heritabilities of breeds other than Holstein may be overestimated because of a small sample population.
Genetic correlations between milk composition percentages are high and positive, averaging 0.Effect of pH and ionic strength Enzymes are amphoteric molecules containing a large number of acid and basic groups, mainly situated on their surface.
The charges on these groups will vary, according to their acid dissociation constants, with the pH of their environment (Table ). Effect of pH: Prepare M pH buffer solutions ranging from pH=1 to pH=12 in increments of one pH unit. Note that the phosphate buffer is only effective for pH= due to the dissociation constant.
How to Digest Protein: Your Health Depends on It. They also require a specific pH, which is the balance of acidity and alkalinity. Enzymes like the stomach to be very acidic. Reignite your digestive fire by learning how to improve protein digestion: Start by .
Effect of PH on Digestion. by JESSICA BRUSO Aug. 14, Enzymes and pH. Enzymes are a type of protein that cause chemical reactions, such as the breakdown of carbohydrates into glucose, protein into amino acids and fat into fatty acids and glycerol.
Different enzymes are more effective at different pH levels. Digestive System pH urbanagricultureinitiative.comd: Jun 17, The Effect of pH on the Activity of the Enzyme Amylase Aim: To find the effect of pH on the activity of the enzyme amylase.
An enzyme is a type of protein found in all living cells. Investigation: Enzymes.
Objectives. Measure the effects of changes in temperature, pH, and enzyme concentration on reaction rates of an enzyme PART C - What is the Effect of Temperature on Catalase Activity? 1. Put a piece of liver into the bottom of a clean test tube and cover it with a small amount of water.
What is the Effect of pH.