Sour cream: Definition and fat content

Sour cream is a relatively heavy, viscous product with a glossy sheen. It has a delicate, lactic acid taste with a balanced, pleasant, buttery-like. American sour cream is heavier-bodied than its European counterpart owing largely to having the cream homogenized twice before being cultured.

The U.S. Food and Drug Administration (FDA) defines sour cream as follows: “Sour cream results from the souring, by lactic acid producing bacteria, of pasteurized cream. Sour cream contains not less than 18 percent milkfat; Sour cream has a titratable acidity of not less than 0.5 percent, calculated as lactic acid.”

Body and Texture: Shall be thick and smooth, uniform, free from lumps or graininess, and spoonable to a soft mound. Flavoring ingredients shall be consistent in size and distribution in the finished product.

Color and Appearance: Shall present a clean, natural color, with a smooth, velvety appearance. Natural color may range from a bright white to a light cream color.

Sour cream, also known as cultured cream, is produced by the fermentation of high pasteurized cream that contains 18–20% fat content. It is then homogenized at a low temperature, to promote formation of homogenization clusters. The starter cultures typically used for making sour cream are aromatic starters (i.e., Lc. lactis subsp. lactis biovar. diacetylactis and L. mesenteroides subsp. cremoris) similar to those used for cultured buttermilk.

Different types of sour creams exist that are defined based on fat content. Full-fat sour creams must have at least 18% milk fat and not less than 14.4% milk fat. Reduced-fat sour cream has a minimum fat reduction of 25%. Light or lite sour cream has a minimum of 50% fat reduction. Low-fat sour cream must contain 3 g or less fat per 50 g and 6% or less total fat. Nonfat sour cream must have less than 0.5 g of fat per 50 g of product and less than 1% total fat.

Sour cream is predominantly utilized as an accompaniment with warm entrees such as baked potatoes and burritos. This usage imposes certain demands on the sensory characteristics of the product, especially with regard to texture when in contact with warm surfaces. Sour cream must remain viscous without whey separation when placed on warm food.

Sour cream is frequently used as a base in dips and sauces. Traditionally, flavors such as onion and spinach have been popular. Currently, the trend is more diverse, with flavors ranging from apricot ginger to chipotle.
Sour cream: Definition and fat content

Separation of fat or cream from milk

Most milk plants separate milk for standardization or the obtain cream for bottling purpose and skim milk for butter milk and cottage cheese.

A layer of cream will form on the top of fresh milk, as it comes from cow, if it is allowed to stand for twenty or thirty minutes. This known as gravity creaming and it was very important prior to the invention of the cream separator. For many years it was customary to heat milk to 85 to 95 °F separation, because at this temperature the difference in density between the fat and skim milk is greatest and results in the most efficient separation of fat from skim milk.

Cream is separated from milk in a cream separator. Cream separator is a heavy metal bowl spinning at a very high speed which sediments the skim milk phase of incoming milk toward the wall of the bowl and displaces the cream inward along the centre of the bowl.

The cream and skim milk can then be recombined in desired ratios to obtain low-fat, light and whole milk with 1%, 2% and 3.25% fat respectively. This standardization usually is performed in a continuous manner.
Separation of fat or cream from milk

Skimmed milk

Milk is highly nutritious food that provides nearly all the substances essential for good health in people of all ages. About 4% of whole milk is fat. The fat that separates from milk is cream. Milk which has had the fat or cream removed is called skimmed milk.

Skimmed milk, which may contain 0.5% fat or less, has been a popular beverage for many years. Skimmed milk is as nutritious as whole milk, but contains much less fat and cholesterol than whole milk.

The fat-soluble vitamins – A, D, E and K - are removed with the fat when milk is skimmed. Consequently, they are present in only trace amounts in skimmed milk and in reduced amounts in semi-skimmed milk. Usually this milk is fortified with vitamins A and D.
Skimmed milk

Cottage cheese

Cottage cheese is a high protein low-fat cheese prepared form curdles milk (curds).  It is usually thought of as a ‘diet’ food, cottage cheese is a healthful food choice when it is made from skim or low-fat milk.

Cottage cheese only retains 25 to 50 percent of the calcium from the milk it is made from, due to the processing. The curdling process leaches calcium from the curds into the liquid called whey, which is removed. The higher the water content of cheeses, such as cottage cheese, the sooner they will go bad.

The total solid (TS) content of the skim milk is often increased to 10-13% by the fortification with non-fat dry milk powder or by the addition of UF retentate.

Cottage cheese is prepared with varying amounts of fat. It is highest in creamed small curd cheese (4.2 percent fat), while low-fat cottage cheese contains 1 percent or 2 percent fat, and dry curd cottage cheese has 0.5 percent fat.
Cottage cheese

What is ghee?

Ghee is clarified butter which means it’s basically butter with the milk solids removed. It is often used in making Indian food. Ghee is sweet in taste and has a cooling potency.

It is anti-aging, nourishing, rejuvenating, good for the eyes, kindles agni, improves digestion, enhances memory, intellect, stamina, immune system and promotes longevity.

Ghee can be used for long, slow frying, for it does not burn quickly as butter would, and it keeps well at room temperature for months in tropical kitchens.

As it turns from butter into ghee, its flavor is transformed to toasted nutty heights, enhancing the dishes in which it is used.

Chemically, ghee is a complex lipid consisting of mixed, FFAs, phospholipids, sterols, sterol esters, soluble vitamins, carbonyls, hydrocarbons, carotenoids, small amounts od charred casein and traces so calcium, phosphorus, iron and zinc.
Ghee

Fat in milk

The fat content and its type are of considerable commercial and nutritional importance to the dairy industry. 

Biologically, due to the high percentage of carbon in fats, they are ‘stored’ nutrients with the highest energy or calorific value of all food constituents.

Milk fat occurs in the form of droplets or globules, surrounded by a membrane and emulsified in milk serum (also called whey).

The fat globule membrane acts as the emulsifying agent for the fat suspended in milk. The membrane protects the fat from enzymes and prevents the globules coalescing into butter grains.

The fat globules (called cream) separate after prolonged storage or after centrifugation. The fat globules float on the skim milk.

Homogenization of milk so finely divides and emulsifies the fat globules that cream separation does not occur even after prolonged standing.

About 98% of milk fat is a mixture of triacyl glycerides. The partial glycerides (diglycerides and monoglycerides) and free fatty acids are probably partly left over from the biosynthesis process.
Fat in milk

Decreaming Process

Decreaming Process
During processing, milk fat is removed partially or completely in order to:

• Obtain a fat-reduced or fat free

• Concentrate milk fat or the production of high fat products

• Standardize the fat content of milk

Decreaming (separation, centrifugation) is the mechanical separation of milk into cream and skim milk by means of centrifugal forces.

The decreaming process has significant economic importance, as it controls the efficiency of the fat separation.

The key objective is to manufacture a skim milk with the lowest possible fat content, which corresponds to good decreaming efficiency. Knowledge of the basics of the fat separation is important for an optimal decreaming process.

Decreaming is based on the facts that fat exists in polydisperse system in an emulsified state and that the specific density difference between milkfat and skim milk is fairly large.

Basically two processes for fat separation are possible, natural decreaming and separation with machine. Natural creaming has no industrial significance.
Decreaming Process

Fat in Milk

Fat in Milk
Fat and associated lipid materials are present in milk as an emulsion of small individual globules in an aqueous phase. These fat globules are predominantly in the liquid state at 37 degree. The fat globules vary in size from about 0.1 to 10 um in diameter.

Surrounding each milk fat globule is a membrane composed of cholesterol, phospholipids, proteins, and other surface-active molecules. The fat globules membrane appears to have two layers: an inner layer that contains a phospholipids-protein complex, and an outer layer that contains enzymes originating in the mammary gland.

The membrane serves to prevent individual fat globules from combining with other to form a larger globule. Mechanical agitation can lead to a disruption of the membrane and thus cause the individual fat globules to coalesce to form larger globules and eventually to form butter. Disruption of the globule membrane may also contribute to the development of rancid flavor in milk.

Milk fat is made up of approximately 12.5% glycerol and 85.5% fatty acids by weight. The predominant glycerides are triglycerides (8-99%); diglycerides account for 0.05%; and monoglycerides for 0.04% of the total. These glycerides contain more than 16 different fatty acids combined with glycerol in a number of different ways.

The principal fatty acids contain an even number of carbon atoms. Milk fat is unique in that it is the only natural food fat that contains butyric acid in its glycerides structure. This fatty acid has a strong characteristics odor. Their release from triglycerides during lipolysis is the cause of rancid odor and flavor in milk.

Milk fat contains a number of minor components. Among these are free fatty acids, cholesterol, phospholipids, and the fat soluble vitamins.
Fat in Milk