HOME

TheInfoList



OR:

Sour cream (in
North American English North American English (NAmE, NAE) is the most generalized variety of the English language as spoken in the United States and Canada. Because of their related histories and cultures, plus the similarities between the pronunciations (accents), ...
,
Australian English Australian English (AusE, AusEng, AuE, AuEng, en-AU) is the set of varieties of the English language native to Australia. It is the country's common language and ''de facto'' national language; while Australia has no official language, Eng ...
and
New Zealand English New is an adjective referring to something recently made, discovered, or created. New or NEW may refer to: Music * New, singer of K-pop group The Boyz Albums and EPs * ''New'' (album), by Paul McCartney, 2013 * ''New'' (EP), by Regurgitator ...
) or soured cream (
British English British English (BrE, en-GB, or BE) is, according to Oxford Dictionaries, "English as used in Great Britain, as distinct from that used elsewhere". More narrowly, it can refer specifically to the English language in England, or, more broadl ...
) is a
dairy product Dairy products or milk products, also known as lacticinia, are food products made from (or containing) milk. The most common dairy animals are cow, water buffalo, nanny goat, and ewe. Dairy products include common grocery store food items i ...
obtained by
fermenting Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food p ...
regular
cream Cream is a dairy product composed of the higher-fat layer skimmed from the top of milk before homogenization. In un-homogenized milk, the fat, which is less dense, eventually rises to the top. In the industrial production of cream, this process ...
with certain kinds of
lactic acid bacteria Lactobacillales are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped ( bacilli) or spherical ( cocci) bacteria that share common metabolic and physiological characteristics. These bact ...
. The bacterial culture, which is introduced either deliberately or naturally, sours and thickens the cream. Its name comes from the production of lactic acid by bacterial fermentation, which is called souring.
Crème fraîche Crème fraîche (English pronunciation: , , lit. "fresh cream") is a dairy product, a soured cream containing 10–45% butterfat, with a pH of approximately 4.5., p. 181''f'' It is soured with a bacterial culture. European labeling regulati ...
is one type of sour cream with a high fat content and less sour taste.


Traditional

Traditionally, sour cream was made by letting cream that was skimmed off the top of milk ferment at a moderate temperature. It can also be prepared by the souring of pasteurized cream with acid-producing bacterial culture. The bacteria that developed during fermentation thickened the cream and made it more acidic, a natural way of preserving it.


Commercial varieties

According to US ( FDA) regulations, commercially produced sour cream contains no less than 18% milkfat before bulking agents are added, and no less than 14.4% milkfat in the finished product. Additionally, it must have a total acidity of no less than 0.5%. It may also contain milk and whey solids, buttermilk, starch in an amount not exceeding one percent, salt, and rennet derived from aqueous extracts from the fourth stomach of calves, kids or lambs, in an amount consistent with good manufacturing practice. In addition, according to the Canadian food regulations, the emulsifying, gelling, stabilizing and thickening agents in sour cream are algin, carob bean gum (locust bean gum),
carrageenan Carrageenans or carrageenins ( ; ) are a family of natural linear sulfated polysaccharides that are extracted from red edible seaweeds. Carrageenans are widely used in the food industry, for their gelling, thickening, and stabilizing properties. T ...
,
gelatin Gelatin or gelatine (from la, gelatus meaning "stiff" or "frozen") is a translucent, colorless, flavorless food ingredient, commonly derived from collagen taken from animal body parts. It is brittle when dry and rubbery when moist. It may also ...
, guar gum,
pectin Pectin ( grc, πηκτικός ': "congealed" and "curdled") is a heteropolysaccharide, a structural acid contained in the primary lamella, in the middle lamella, and in the cell walls of terrestrial plants. The principal, chemical component o ...
, or
propylene glycol alginate Propylene glycol alginate (PGA) is an emulsifier, stabilizer, and thickener used in food products. It is a food additive with E number E405. Chemically, propylene glycol alginate is an ester of alginic acid, which is derived from kelp ...
or any combination thereof in an amount not exceeding 0.5 percent, monoglycerides, mono- and diglycerides, or any combination thereof, in an amount not exceeding 0.3 percent, and sodium phosphate dibasic in an amount not exceeding 0.05 percent. Sour cream is not fully fermented, and like many dairy products, must be
refrigerated The term refrigeration refers to the process of removing heat from an enclosed space or substance for the purpose of lowering the temperature.International Dictionary of Refrigeration, http://dictionary.iifiir.org/search.phpASHRAE Terminology, ht ...
unopened and after use. Additionally, in Canadian regulations, a milk-coagulating enzyme derived from ''Rhizomucor miehei'' (Cooney and Emerson) from ''Mucor pusillus Lindt'' by pure culture fermentation process or from Aspergillus oryzae RET-1 (pBoel777) can also be added into sour cream production process, in an amount consistent with good manufacturing practice. Sour cream is sold with an expiration date stamped on the container, though whether this is a "sell by", a "best by" or a "use by" date varies with local regulation. Refrigerated unopened sour cream can last for 1–2 weeks beyond its ''sell by date''. Once it has been opened, refrigerated sour cream generally lasts for 7–10 days.


Physical-chemical properties


Ingredients

Cultured cream. Processed sour cream can include any of the following additives and preservatives: grade A whey, modified food starch, sodium phosphate,
sodium citrate Sodium citrate may refer to any of the sodium salts of citric acid (though most commonly the third): * Monosodium citrate * Disodium citrate * Trisodium citrate The three forms of salt are collectively known by the E number E331. Applications ...
, guar gum,
carrageenan Carrageenans or carrageenins ( ; ) are a family of natural linear sulfated polysaccharides that are extracted from red edible seaweeds. Carrageenans are widely used in the food industry, for their gelling, thickening, and stabilizing properties. T ...
,
calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hydrate is better known as plaster of Paris ...
, potassium sorbate, and locust bean gum.


Processing

The manufacturing of sour cream begins with the standardization of fat content; this step is to ensure that the desired or legal amount of milk fat is present. As previously mentioned the minimum amount of milk fat that must be present in sour cream is 18%. During this step in the manufacturing process other dry ingredients are added to the cream; additional grade A whey for example would be added at this time. Another additive used during this processing step are a series of ingredients known as stabilizers. The common stabilizers that are added to sour cream are
polysaccharides Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with w ...
and
gelatin Gelatin or gelatine (from la, gelatus meaning "stiff" or "frozen") is a translucent, colorless, flavorless food ingredient, commonly derived from collagen taken from animal body parts. It is brittle when dry and rubbery when moist. It may also ...
, including modified food starch, guar gum, and
carrageenan Carrageenans or carrageenins ( ; ) are a family of natural linear sulfated polysaccharides that are extracted from red edible seaweeds. Carrageenans are widely used in the food industry, for their gelling, thickening, and stabilizing properties. T ...
s. The reasoning behind the addition of stabilizers to fermented dairy products is to provide smoothness in the body and texture of the product. The stabilizers also assist in the gel structure of the product and reduce whey syneresis. The formation of these gel structures, leaves less free water for whey syneresis, thereby extending the shelf life. Whey syneresis is the loss of moisture by the expulsion of whey. This expulsion of whey can occur during the transportation of containers holding the sour cream, due to the susceptibility to motion and agitation. The next step in the manufacturing process is the acidification of the cream.
Organic acids An organic acid is an organic compound with acidic properties. The most common organic acids are the carboxylic acids, whose acidity is associated with their carboxyl group –COOH. Sulfonic acids, containing the group –SO2OH, are r ...
such as
citric acid Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in ...
or
sodium citrate Sodium citrate may refer to any of the sodium salts of citric acid (though most commonly the third): * Monosodium citrate * Disodium citrate * Trisodium citrate The three forms of salt are collectively known by the E number E331. Applications ...
are added to the cream prior to
homogenization Homogeneity is a sameness of constituent structure. Homogeneity, homogeneous, or homogenization may also refer to: In mathematics *Transcendental law of homogeneity of Leibniz * Homogeneous space for a Lie group G, or more general transformatio ...
in order to increase the metabolic activity of the starter culture. To prepare the mixture for homogenization, it is heated for a short period of time. Homogenization is a processing method that is utilized to improve the quality of the sour cream in regards to the color, consistency, creaming stability, and creaminess of the cultured cream. During homogenization larger fat globules within the cream are broken down into smaller sized globules to allow an even suspension within the system. At this point in the processing the milk fat globules and the casein
proteins Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
are not interacting with each other, there is repulsion occurring. The mixture is homogenized, under high pressure homogenization above 130
bar (unit) The bar is a metric unit of pressure, but not part of the International System of Units (SI). It is defined as exactly equal to 100,000  Pa (100 kPa), or slightly less than the current average atmospheric pressure on Earth at sea l ...
and at a high temperature of 60 °C. The formation of the small globules (below 2 microns in size) previously mentioned allows for reducing a cream layer formation and increases the
viscosity The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the int ...
of the product. There is also a reduction in the separation of whey, enhancing the white color of the sour cream. After homogenization of the cream, the mixture must undergo
pasteurization Pasteurization or pasteurisation is a process of food preservation in which packaged and non-packaged foods (such as milk and fruit juices) are treated with mild heat, usually to less than , to eliminate pathogens and extend shelf life. ...
. Pasteurization is a mild heat treatment of the cream, with the purpose of killing any harmful bacteria in the cream. The homogenized cream undergoes high temperature short time (HTST) pasteurization method. In this type of pasteurization the cream is heated to the high temperature of 85 °C for thirty minutes. This processing step allows for a sterile medium for when it is time to introduce the starter bacteria. After the process of pasteurization, there is a cooling process where the mixture is cooled down to a temperature of 20˚C. The reason that the mixture was cooled down to the temperature of 20˚C is due to the fact that this is an ideal temperature for mesophilic inoculation. After the homogenized cream has been cooled to 20˚C, it is inoculated with 1-2% active starter culture. The type of starter culture utilized is essential for the production of sour cream. The
starter culture A fermentation starter (called simply starter within the corresponding context, sometimes called a mother) is a preparation to assist the beginning of the fermentation process in preparation of various foods and alcoholic drinks. Food groups wh ...
is responsible for initiating the fermentation process by enabling the homogenized cream to reach the pH of 4.5 to 4.8. Lactic acid bacteria (hereto known as LAB) ferment lactose to lactic acid, they are mesophilic,
Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bact ...
facultative anaerobes. The strains of LAB that are utilized to allow the fermentation of sour cream production are Lactococcus lactis subsp latic or Lactococcus lactis subsp cremoris they are lactic acid bacteria associated with producing the acid. The LAB that are known for producing the aromas in sour cream are Lactococcus lactis ssp. lactis biovar diacetyllactis. Together these bacteria produce compounds that will lower the pH of the mixture, and produce flavor compounds such as
diacetyl Diacetyl (IUPAC systematic name: butanedione or butane-2,3-dione) is an organic compound with the chemical formula (CH3CO)2. It is a yellow liquid with an intensely buttery flavor. It is a vicinal diketone (two C=O groups, side-by-side). Diacet ...
. After the inoculation of starter culture, the cream is portioned in packages. For 18 hours a fermentation process takes place in which the pH is lowered from 6.5 to 4.6. After fermentation, one more cooling process takes place. After this cooling process, the sour cream is packaged into their final containers and sent to the market.


Physical-chemical changes

During the pasteurization process, temperatures are raised past the point where all the particles in the system are stable. When cream is heated to temperatures above 70 °C, there is denaturation of whey proteins. To avoid phase separation brought on by the increased surface area, the fat globules readily bind with the denatured β-lactoglobulin. The adsorption of the denatured whey proteins (and whey proteins that bound with casein micelles) increases the number of structural components in the product; the texture of sour cream can be partly attributed to this. The denaturation of whey proteins is also known for increasing the strength of the
cross-link In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural ...
ing within the cream system, due to the formation of whey protein polymers. When the cream is inoculated with starter bacteria and the bacteria begins converting lactose to lactic acid, the pH begins a slow decrease. When this decrease begins, dissolution of calcium phosphate occurs, and causes a rapid drop in the pH. During the processing step, fermentation the pH was dropped from 6.5 to 4.6, this drop in pH brings on a physicochemical change to the casein micelles. Recall the casein proteins are heat stable, but they are not stable in certain acidic conditions. The colloidal particles are stable at the normal pH of milk which is 6.5-6.7, the micelles will precipitate at the isoelectric point (pI) of milk which is a pH of 4.6. At a pH of 6.5 the casein micelles repulse each other due to the electronegativity of the outer layer of the micelle. During this drop in pH there is a reduction in zeta potential, from the highly net negative charges in cream to no net charge when approaching the pI. U_E= \left \lfloor \frac \right \rfloor The formula shown is the Henry's equation, where z: zeta potential, Ue: electrophoretic mobility, ε: dielectric constant, η: viscosity, and f(ka): Henry's function. This equation is used to find the zeta potential, which is calculated to find the
electrokinetic potential Zeta potential is the electrical potential at the slipping plane. This plane is the interface which separates mobile fluid from fluid that remains attached to the surface. Zeta potential is a scientific term for electrokinetic potential in coll ...
in colloidal dispersions. Through electrostatic interactions the casein molecules begin approaching and aggregating together. The casein proteins enter a more ordered system, attributing to a strong gel structure formation. The whey proteins that were denatured in the heating steps of processing, are insoluble at this acidic pH and are precipitated with casein. The interactions involved in gelation and aggregation of casein micelles are hydrogen bonds, hydrophobic interactions, electrostatic attractions and van der Waals attractions These interactions are highly dependent on pH, temperature and time. At the isoelectric point, the net surface charge of casein micelle is zero and a minimum of electrostatic repulsion can be expected. Furthermore, aggregation is taking place due to dominating hydrophobic interactions. Differences in the zeta potential of milk can be caused by differences in ionic strength differences, which in turn depend on the amount of calcium present in the milk. The stability of milk is largely due to the electrostatic repulsion of casein micelles. These casein micelles aggregated and precipitated when they approach the absolute zeta potential values at pH 4.0 – 4.5. When the heat treated and denatured, whey protein is covering the casein micelle, isoelectric point of the micelle elevated to the isoelectric point of β lactoglobulin (approximately pH 5.3).


Rheological properties

Sour cream exhibits time-dependent thixotropic behaviors. Thixotropic fluids reduce in viscosity as work is applied, and when the product is no longer under stress, the fluid returns to its previous viscosity. The viscosity of sour cream at room temperature is 100,000 cP, (for comparison: water has a viscosity of 1 cP at 20 °C). The thixotropic properties exhibited by sour cream are what make it such a versatile product in the food industry.


Uses

Sour cream is commonly used as a
condiment A condiment is a preparation that is added to food, typically after cooking, to impart a specific flavor, to enhance the flavor, or to complement the dish. A table condiment or table sauce is more specifically a condiment that is served separat ...
on foods, or combined with other ingredients to form a
dipping sauce A dip or dipping sauce is a common condiment for many types of food. Dips are used to add flavor or texture to a food, such as pita bread, dumplings, crackers, chopped raw vegetables, fruits, seafood, cubed pieces of meat and cheese, pot ...
. It can be added to soups and sauces to help thicken and make them creamy, or in baking to help increase the moisture level over and above using milk. In Tex-Mex cuisine, it is often used as a substitute for crema in
nachos Nachos are a Mexican culinary dish consisting of fried tortilla chips or ''totopos'' covered with melted cheese or cheese sauce, as well as a variety of other toppings and garnishes, often including meats (such as ground beef or grilled chicken ...
,
taco A taco (, , ) is a traditional Mexican food consisting of a small hand-sized corn- or wheat-based tortilla topped with a filling. The tortilla is then folded around the filling and eaten by hand. A taco can be made with a variety of fillin ...
s, burritos, and taquitos.


See also

* Crema *
Crème fraîche Crème fraîche (English pronunciation: , , lit. "fresh cream") is a dairy product, a soured cream containing 10–45% butterfat, with a pH of approximately 4.5., p. 181''f'' It is soured with a bacterial culture. European labeling regulati ...
*
Cream cheese Cream cheese is a soft, usually mild-tasting fresh cheese made from milk and cream.Oxford English Dictionary Stabilizers such as carob bean gum and carrageenan are often added in industrial production. The U.S. Food and Drug Administration de ...
*
Fermented milk products Fermented milk products or fermented dairy products, also known as cultured dairy foods, cultured dairy products, or cultured milk products, are dairy foods that have been fermented with lactic acid bacteria such as '' Lactobacillus'', '' Lacto ...
*
List of dairy products This is a list of dairy products. A dairy product is food produced from the milk of mammals. A production plant for the processing of milk is called a dairy or a dairy factory. Dairy farming is a class of agricultural, or an animal husbandry, ente ...
* List of dips * Smetana * Pomazánkové máslo * Souring *
Yogurt Yogurt (; , from tr, yoğurt, also spelled yoghurt, yogourt or yoghourt) is a food produced by bacterial fermentation of milk. The bacteria used to make yogurt are known as ''yogurt cultures''. Fermentation of sugars in the milk by these bac ...


References


Further reading

* * —notes on the industrial production process for sour cream and yogurt.


External links

* {{Salad dressings Fermented dairy products Sour foodsy: Dairy products Condiments Mexican cuisine Western cuisine English cuisine British cuisine European cuisine Israeli cuisine Mediterranean cuisine North American cuisine Central American cuisine South American cuisine Australian cuisine Canadian cuisine New Zealand cuisine