Sour cream, acidic

Cells of microorganisms have constituted a portion of human food siace ancient times. Yeast-leavened baked products contain the residual nutrients from the yeast cells destroyed duriag bakiag (see Bakery processes and leavening agents). Cultured dairy products, such as yogurt, buttermilk, and sour cream, contain up to lO cells of lactic acid bacteria per gram (19) (see Milk and milkproducts). Other examples of fermented foods consumed siace early times iaclude fermented meats, fish, and soybean products. 

Acids and bases are determined by their properties. The word acid comes from the Latin word acidus, which means sour. For example, lemon juice tastes sour because it contains citric acid. Sauerkraut, another sour-tasting food, is cabbage fermented in lactic acid. In fact, sauer (pronounced almost exactly like the English word sour) in German means acid. Sour cream also has lactic acid in it. 

Sour cream is cream that has been soured by lactic acid bacteria or by directly adding food-grade acids. According to U.S. federal standards, both sour cream and acidified sour cream must contain not less than 18% milk fat with a titratable acidity of not less than 0.5% expressed as lactic acid (FDA 1981A). Optional ingredients are used to improve... 

Milk can be converted easily by lactic acid starter cultures into various cultured and culture-containing milk products. Within the last ten years, consumption of these products (e.g., yogurt, sour cream, and acidophilus milk) has increased appreciably in the United States. (Rasic and Kurmann 1978 Shahani and Chandan 1979 Helferich and... 

Taste is only one of several qualities of a process or product that is affected by an excess of either of these 10ns. Some raw materials are naturally too acidic, others too alkaline—so that neutralizers must be added to adjust the pH within an acceptable range. In die dairy industry, for example, the acid in sour cream must be adjusted by the addition of alkaline compounds in order that satisfactory butter can be churned. Quite often, the pH may be difficult to adjust or to maintain after adjustment. Stability of pH can be accomplished by the addition of buffering agents that, within limits, effectively maintain the desired pH even when additional acid or alkali is added. For example, orange-flavored instant breakfast drink has just... 

Lactic Fermentation—in which lactic acid is produced. This is an important fermentation for the preservation of food. Ixtclohacillits bitlgaricus. L, casei. and Streptococcus lartis are used for the manufacture of dairy products, such as sour cream. Lactobacillus plunlariim is used in lhe preservation of certain vegetables, such as the production of pickles and kraut. 

Butter (Irish sour cream) 2,3-Butanedione, (R)-<5-decalactone, butanoic acid, (Z)-7-6-dodecenolactone (160) 182... 

Farmer sour cream (FSC) Rancid, like butanoic acid 3... 

Many examples of acid-base reactions can be found in cooking, such as the soda-sour cream reaction in Little Men. In addition, the unfortunate result of acid rain (the formation of which we will discuss later) is that the acid in the rain reacts with the carbonates found in limestone and marble, which causes the deterioration of statues, some of which had managed to survive without corrosion for thousands of years before the advent of the industrial age. (But before one completely condemns the industrial age, it should be remembered that the bacteria of Black Death, smallpox, and syphilis also managed to survive for thousands of years before modem technology brought them to bay.) This ability of acid rain to dissolve marble brings up another property common to all acids and bases they are corrosive. 

Low Molecular Weight Carbonyl Compounds. In the dairy field, a major product made this way is starter distillate. The main component is diaceyl which is a very important aroma compound responsible for the characteristic buttery flavor of fermented dairy products such as sour cream or buttermilk. The dairy industry relies upon fermentation by lactic streptococci for the production of diacetyl in cultured products. Starter distillate is a natural product rich in diacetyl which is produced by distilling such lactic cultures. The key intermediate in the biosynthesis of diacetyl is aL-acetolactic acid which is decarboxylated to form diacetyl (Figure 3). The starting material of the biosynthetic pathway is citrate which is a natural component of milk. 

The major problem has been the partial or complete inhibition of acid production by dairy starter cultures used in the manufacture of cheese, buttermilk, sour cream or yogurt... 

In the food industry LC is frequently used to determine the quality of the finished product. For example, it has been shown that the flavor quality of grape juice is directly linked to the amount and spectrum of organic acids present. Likewise, in the production of sour cream by fermentation, the quality of the finished product quality is related directly to the organic acid profile. Last, but not least and as pointed out above, LC techniques are also crucial in determining the quality of recombinant protein products. 

Acidic (generic see specific acids) Sour cream ( soumess and apples) see also acetic and lactic. 30-280 Varies with acid see individual acids Lactobacillus spps. (see details in Table 18.1) ( Acetomonas). Microorganisms may produce various acids and give a sour/tart note to beer. 

Recent studies of photooxidized butter and butter oil identified by aroma extract dilution analysis, 3-methylnonane-2,4-dione, a potent volatile compound derived from furanoid fatty acids (see Section C.4) (Figure 11.7). Six different furanoid fatty acids were established as dione precursors, and were found in various samples of butter made from either sweet cream (116 76 mg/ kg), or from sour cream (153-173 mg/kg), or from butter oil (395 mg/kg). Similar precursors of the dione were identified in stored boiled beef and vegetable oils. This flavor defect arising by photooxidation of butter or butter oil is apparently different from the light-activated flavor in milk,that involves the interaction of sulfur-containing proteins and riboflavin. However, more sensory comparisons are needed to distinguish between these two flavor defects due to light oxidation. 

Industrial Fermentation. The primary and largest industry revolves around food products. Milk from cows, sheep, goats, and horses have traditionally been used for the production of fermented dairy products. These products include cheese, sour cream, kefir, and yogurt. More recently so-called probiotics appeared and have been marketed as health-food drinks. Dairy products are produced via fermentation using lactic bacteria such as Lactobacillus acidophilus and Bifidobacterium. Fungi are also involved in making some cheeses. Fermentation produces lactic acid and other flavors and aroma compounds that make dairy products taste good. 

Seasonings based on dairy products — Cheeses and sour creams are commonly used in snack seasonings. Natural cheeses are often used for label or familiarity purposes. Enzyme modified cheeses or creams are typically used to carry the flavor due to both flavor strength and cost issues. The dairy character of the seasoning may be fortified with other natural flavorings, e.g., lactic acid, butyric acid, diacetyl, etc. Examples of dairy-based snack seasonings are presented in Table 14.6 and Table 14.7. 

Homofermentative lactic acid bacteria (such as Lactococcus lactis and Streptococcus lactis) produce (-l-)-L-lactic acid (e.g. in sour cream). Both isomers, (-l-)-L-lactic acid and (-)-D-lactic acid (8-65), are formed during milk fermentation by heterofermen-tative bacteria (lactic acid bacteria are mostly heterofermentative bacteria) and lactic acid thus also occurs as a racemate in sauerkraut, pickled cucumbers, olives and silage. For example, bacteria of the genus Leuconostoc produce d-lactic acid, while bacteria Pediococcus acidilactici and other bacteria produce racemic lactic acid. The content of lactic acid in dairy products is 0.5-1.0%. L-Lactic acid in yoghurt represents about 54% and in sour cream 96% of the total lactic acid content. The total lactic acid content in sauerkraut is 1.5 2.5%, in fermented cucumbers it ranges from 0.5 to 1.5% and fermented green olives contain 0.8 to 1.2% lactic acid. 

The aroma of butter made from sweet cream is affected primarily by free fatty acids (especially capric and lauric acids), S- and y-lactones, dimethylsulfide, (Z)-hept-4-enal and the degradation products of tryptophan (indole and skatole). The butter obtained from sour cream contains mainly metabolic products of microorganisms (so-called starter cultures). Especially important compounds are biacetyl, lactic and acetic acids. 

Raw cucumbers or pickles may be diced or sliced and added to relish trays, salads, and sandwiches. It is noteworthy that the slightly bitter flavor of the raw vegetable is improved by dressing with acid-flavored items such as lemon juice, mayonnaise, sour cream, vinegar, and yogurt whereas pickles are acid-flavored to begin with, and have no need for such dressing. 

Buckwheat flour Fleur (roiti dehulled buckwheat. Preparation ot buckwheat pancakes and blintzes (rolled thin pancakes filled ot served with fish, fiuil, meat, and/or sour cream), Similar lo that ol wheat llcui, exc t that amino acid patterns ol the 2 Hours are complementary, (Hence, mixtures of Ihe flours ate more nutritious than either one alone.) This flour has a rich hearty llavor and produ( s baked goods that are a little heavier and moisler than wheat flout Items. 

CULTURED MILK AND OTHER PRODUCTS. Cultured milks are fluid products that result from the souring of milk or its products by bacteria that produce lactic acid, whereeis acidified milks are obtained by the addition of food-grade acids to produce an acidity of not less than 0.20%, expressed as lactic acid. The word cultured is used because pure bacterial cultures are employed in commercial manufacture. It is proper also to use the words fermented or sour because lactic acid, which imparts sourness, is produced by fermentation of milk sugar (lactose). Kefir, koumiss, acidophilus milk, cultured buttermilk, sour cream, and yogurt are examples of lactic acid fermentations. 

Sour cream or cultured sour cream—Pasteurized, homogenized cream cultured with Streptococcus lactls at 71.6°F (22°C) until the acidity is at least 0.5%, calculated... 

Acidified sour cream— This product results from the souring of pasteurized cream with safe and suitable acidifiers, with or without the addition of lactic acid producing bacteria. Federal standards of identity call for not less than 18% milkfat and a titratable acidity of not less than 0.5% calculated as lactic acid. In the event nutritive sweeteners or bulky flavoring ingredients are added, the product may not contain less than 14.4% milkfat. 

Quick breads, unlike yeast breads, are simply mixed and baked, relying on the rising action of baking powder or baking soda combined with an acidic element such as buttermilk, yogurt, or sour cream. Quick breads can be savory, such as biscuits, or sweet, like a loaf of banana bread. Experienced cooks can make a batch of biscuits, start to finish, in about seventeen minutes, so they truly are quick. 

Most of the SCP produced currently is for animal consumption. Minor quantitites of SCP are being produced for human use. This use has been controversial because of the content of nucleic acid, which can increase blood uric acid levels in a segment of the population. However, many traditional foods contain SCP, such as cheese, yogurt, and sour cream. 

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