Apple Cider Vinegar Research 2016
-ACV and weight loss. ACV “may turn on certain genes involved in breaking down fats” and thus help weight loss, according to WebMD.com. A study of 175 obese people in Japan showed that taking daily ACV helped slightly in weight loss.
ACV suppresses glycemic index: Carol Johnston, PhD, director of Arizona State University’s nutrition program, has studied apple cider vinegar for more than 10 years and believes its effects on blood sugar are similar to certain medications. “Apple cider vinegar’s anti-glycemic effect is very well documented,” Johnston says, per WebMD.com. This only works hand in hand with diet changes -- you can’t just have ACV and say gee, I don’t have to worry about getting Type 2 Diabetes anymore!
Debbie Davis, RD, recommends using unfiltered apple cider vinegar, “the cloudy kind, where you can see a blob in the bottle” (which is what we are learning to make in this class). That blob, the Mother of Vinegar, is full of probiotics and other beneficial bacteria. “This kind of vinegar can support immune function and, for some people, even help with constipation,” Davis says, per WebMD.com.
Don't drink it straight. It’s so acidic that it could harm your tooth enamel and your esophagus, per WebMD.com.
Don't use a lot. “Dilute 1 to 2 tablespoons in a big glass of water, and sip it along with your meals one or two times a day,” Johnston says, per WebMD.com.
Vinegar: Medicinal Uses and Antiglycemic Effect
Vinegar folklore is as colorful as it is practical. Legend states that a courtier in Babylonia (c. 5000 BC) “discovered” wine, formed from unattended grape juice, leading to the eventual discovery of vinegar and its use as a food preservative. Hippocrates (c. 420 BC) used vinegar medicinally to manage wounds. Hannibal of Carthage (c. 200 BC), the great military leader and strategist, used vinegar to dissolve boulders that blocked his army's path. Cleopatra (c. 50 BC) dissolved precious pearls in vinegar and offered her love potion to Anthony. Sung Tse, the 10th century creator of forensic medicine, advocated hand washing with sulfur and vinegar to avoid infection during autopsies. Based on the writings of US medical practitioners dating to the late 18th century, many ailments, from dropsy to poison ivy, croup, and stomachache, were treated with vinegar, and, before the production and marketing of hypoglycemic agents, vinegar “teas” were commonly consumed by diabetics to help manage their chronic aliment. This review examines the scientific evidence for medicinal uses of vinegar, focusing particularly on the recent investigations supporting vinegar's role as an antiglycemic agent. Epidemiologic studies and clinical trials were identified by a MEDLINE title/abstract search with the following search terms: vinegar, glucose; vinegar, cancer; or vinegar, infection. All relevant randomized or case-control trials were included in this review.
Readers are encouraged to respond to George Lundberg, MD, Editor of MedGenMed, for the editor's eye only or for possible publication via email: ten.epacsdem@grebdnulg
Vinegar, from the French vin aigre, meaning “sour wine,” can be made from almost any fermentable carbohydrate source, including wine, molasses, dates, sorghum, apples, pears, grapes, berries, melons, coconut, honey, beer, maple syrup, potatoes, beets, malt, grains, and whey. Initially, yeasts ferment the natural food sugars to alcohol. Next, acetic acid bacteria (Acetobacter) convert the alcohol to acetic acid. Commercial vinegar is produced by either fast or slow fermentation processes. For the quick methods, the liquid is oxygenated by agitation and the bacteria culture is submerged permitting rapid fermentation. The slow methods are generally used for the production of the traditional wine vinegars, and the culture of acetic acid bacteria grows on the surface of the liquid and fermentation proceeds slowly over the course of weeks or months. The longer fermentation period allows for the accumulation of a nontoxic slime composed of yeast and acetic acid bacteria, known as the mother of vinegar. Vinegar eels (nematodaTurbatrix aceti) feed on these organisms and occur in naturally fermenting vinegar. Most manufacturers filter and pasteurize their product before bottling to prevent these organisms from forming. After opening, mother may develop in stored vinegar; it is considered harmless and can be removed by filtering. Many people advocate retaining the mother for numerous, but unsubstantiated, health effects.
The chemical and organoleptic properties of vinegars are a function of the starting material and the fermentation method. Acetic acid, the volatile organic acid that identifies the product as vinegar, is responsible for the tart flavor and pungent, biting odor of vinegars. However, acetic acid should not be considered synonymous with vinegar. The US Food and Drug Administration (FDA) states that diluted acetic acid is not vinegar and should not be added to food products customarily expected to contain vinegar. Other constituents of vinegar include vitamins, mineral salts, amino acids, polyphenolic compounds (eg, galic acid, catechin, caffeic acid, ferulic acid), and nonvolatile organic acids (eg, tartaric, citric, malic, lactic).[4,5]
In the United States, vinegar products must contain a minimum of 4% acidity. European countries have regional standards for vinegar produced or sold in the area. White distilled vinegars are generally 4% to 7% acetic acid whereas cider and wine vinegars are 5% to 6% acetic acid. Specialty vinegars are grouped as herbal or fruit vinegars. Herbal vinegars consist of wine vinegars or white distilled vinegars, which may be seasoned with garlic, basil, tarragon, cinnamon, clove, or nutmeg. Fruit vinegars are wine and white vinegars sweetened with fruit or fruit juice to produce a characteristic sweet-sour taste. Traditional vinegars are produced from regional foods according to well-established customs. The balsamic vinegar of Modena, Italy, is made from the local white Trebbiano grapes, which are harvested as late as possible, fermented slowly, and concentrated by aging in casks of various woods. Traditional rice wine vinegars are produced in Asia, coconut and cane vinegars are common in India and the Philippines, and date vinegars are popular in the Middle East.
Medicinal Uses of Vinegar
The use of vinegar to fight infections and other acute conditions dates back to Hippocrates (460-377 BC; the father of modern medicine), who recommended a vinegar preparation for cleaning ulcerations and for the treatment of sores. Oxymel, a popular ancient medicine composed of honey and vinegar, was prescribed for persistent coughs by Hippocrates and his contemporaries, and by physicians up to modern day. The formulation of oxymel was detailed in the British Pharmacopoeia (1898) and the German Pharmacopoeia (1872), and, according to the French Codex (1898), the medicine was prepared by mixing virgin honey, 4 parts, with white wine vinegar, 1 part, concentrating and clarifying with paper pulp.
Recent scientific investigations clearly demonstrate the antimicrobial properties of vinegar, but mainly in the context of food preparation.[9–12] Experts advise against using vinegar preparations for treating wounds. At concentrations nontoxic to fibroblasts and keratinocytes (≤ 0.0025%), acetic acid solutions were ineffective at inhibiting the growth of Escherichia coli, group D Enterococcus, or Bacteroides fragilisbacteria, and only slightly effective at inhibiting the growth of Staphylococcus aureus and Pseudomonas aeruginosa bacteria. Similarly, experts caution against using vinegar as a household disinfectant against human pathogens because chemical disinfectants are more effective.[14,15] However, undiluted vinegar may be used effectively for cleaning dentures, and, unlike bleach solutions, vinegar residues left on dentures were not associated with mucosal damage.
Although investigations have demonstrated the effectiveness of diluted vinegar (2% acetic acid solution at pH 2) for the treatment of ear infections (otitis externa, otitis media, and granular myringitis),[17,18] the low pH of these solutions may irritate inflamed skin and damage cochlear outer hair cells. Immediate vinegar application at the site of jellyfish stings is practiced at various coastal locations around the world[20,21] because vinegar deactivates the nematocysts. However, hot-water immersion is considered the most efficacious initial treatment for jellyfish envenomation because the venom is deactivated by heat.[22,23]
In the popular media, vinegar is commonly recommended for treating nail fungus, head lice, and warts, yet scientific support for these treatment strategies is lacking. Takano-Lee and colleagues demonstrated that, of 7 home remedies tested, vinegar was the least effective for eliminating lice or inhibiting the hatching of eggs. Scattered reports suggest that the successive topical application of highly concentrated acetic acid solutions (up to 99%) alleviated warts,[25,26] presumably due to the mechanical destruction of wart tissue. One treatment protocol, however, required local anesthesia, excision, and rapid neutralization at the site of application, thus limiting its use by the lay public.
Although not a treatment modality, vinegar washes are used by midwives in remote, poorly resourced locations (eg, Zimbabwe and the Amazon jungle) to screen women for the human papilloma virus infection.[27,28] Contact with acetic acid causes visual alterations of the viral lesions permitting rapid detection of infection with 77% sensitivity and the option of immediate treatment with cryotherapy.
Kondo and colleagues reported a significant reduction in systolic blood pressure (approximately 20 mm Hg) in spontaneously hypertensive (SHR) rats fed a standard laboratory diet mixed with either vinegar or an acetic acid solution (approximately 0.86 mmol acetic acid/day for 6 weeks) as compared with SHR rats fed the same diet mixed with deionized water. These observed reductions in systolic blood pressure were associated with reductions in both plasma renin activity and plasma aldosterone concentrations (35% to 40% and 15% to 25% reductions in renin activity and aldosterone concentrations, respectively, in the experimental vs control SHR rats). Others have reported that vinegar administration (approximately 0.57 mmol acetic acid, orally) inhibited the renin-angiotensin system in nonhypertensive Sprague-Dawley rats.
Trials investigating the effects of vinegar ingestion on the renin-angiotensin system have not been conducted in humans, and there is no scientific evidence that vinegar ingestion alters blood pressure in humans. In their report, Kondo and colleagues speculated that dietary acetic acid promoted calcium absorption and thereby downregulated the renin-angiotensin system. In the rat model, acetic acid administration enhanced calcium absorption and retention; moreover, in humans, calcium absorption in the distal colon was enhanced by acetate. Clearly, much work is needed to establish whether vinegar ingestion alters calcium absorption and/or blood pressure regulation in humans.
Whether chronic vinegar ingestion affects other risk factors for cardiovascular disease in humans is not known. Hu and colleagues reported a significantly lower risk for fatal ischemic heart disease among participants in the Nurses' Health Study who consumed oil-and-vinegar salad dressings frequently (5-6 times or more per week) compared with those who rarely consumed them (multivariate RR: 0.46; CI: 0.27-0.76, P for trend = .001). Frequent consumption of mayonnaise or other creamy salad dressings was not significantly associated with risk for ischemic heart disease in this population (multivariate RR: 0.84; CI: 0.50-1.44, P for trend = .44). The study authors contend that because oil and vinegar dressings are a major dietary source of dietary alpha-linolenic acid, an antiarrhythmic agent, alpha-linolenic acid may potentially be the beneficial ingredient of this food. Yet, creamy, mayonnaise-based salad dressings are also rich in alpha-linolenic acid and did not show the same risk benefit as the oil and vinegar dressings.
In vitro, sugar cane vinegar (Kibizu) induced apoptosis in human leukemia cells, and a traditional Japanese rice vinegar (Kurosu) inhibited the proliferation of human cancer cells in a dose-dependent manner. An ethyl acetate extract of Kurosu added to drinking water (0.05% to 0.1% w/v) significantly inhibited the incidence (−60%) and multiplicity (−50%) of azoxymethane-induced colon carcinogenesis in male F344 rats when compared with the same markers in control animals. In a separate trial, mice fed a rice-shochu vinegar-fortified feed (0.3% to 1.5% w/w) or control diet were inoculated with sarcoma 180 (group 1) or colon 38 (group 2) tumor cells (2 × 106 cells subcutaneously). At 40 days post-inoculation, vinegar-fed mice in both experimental groups had significantly smaller tumor volumes when compared with their control counterparts. A prolonged life span due to tumor regression was also noted in the mice ingesting rice-shochu vinegar as compared with controls, and in vitro, the rice-shochu vinegar stimulated natural killer cell cytotoxic activity.
The antitumor factors in vinegar have not been identified. In the human colonic adenocarcinoma cell line Caco-2, acetate treatment, as well as treatment with the other short-chain fatty acids (SCFA) n-butyrate and propionate, significantly prolonged cell doubling time, promoted cell differentiation, and inhibited cell motility. Because bacterial fermentation of dietary fiber in the colon yields the SCFA, the investigators concluded that the antineoplastic effects of dietary fiber may relate in part to the formation of SCFA. Others have also documented the antineoplastic effects of the SCFA in the colon, particularly n-butyrate. Thus, because acetic acid in vinegar deprotonates in the stomach to form acetate ions, it may possess antitumor effects.
Vinegars are also a dietary source of polyphenols, compounds synthesized by plants to defend against oxidative stress. Ingestion of polyphenols in humans enhances in vivo antioxidant protection and reduces cancer risk. Kurosu vinegar is particularly rich in phenolic compounds, and the in-vitro antioxidant activity of an ethyl acetate extract of Kurosu vinegar was similar to the antioxidant activity of alpha-tocopherol (vitamin E) and significantly greater than the antioxidant activities of other vinegar extracts, including wine and apple vinegars. Kurosu vinegar extracts also suppressed lipid peroxidation in mice treated topically with H2O2-generating chemicals. Currently, much interest surrounds the role of dietary polyphenols, particularly from fruits, vegetables, wine, coffee, and chocolate, in the prevention of cancers as well as other conditions including cardiovascular disease; perhaps vinegar can be added to this list of foods and its consumption evaluated for disease risk.
Epidemiologic data, however, is scarce and unequivocal. A case-control study conducted in Linzhou, China, demonstrated that vinegar ingestion was associated with a decreased risk for esophageal cancer (OR: 0.37). However, vinegar ingestion was associated with a 4.4-fold greater risk for bladder cancer in a case-control investigation in Serbia.
Blood Glucose Control
The antiglycemic effect of vinegar was first reported by Ebihara and Nakajima in 1988. In rats, the blood glucose response to a 10% corn starch load was significantly reduced when coadministered with a 2% acetic acid solution. In healthy human subjects, although the glucose response curve was not significantly altered, the area under the insulin response curve following the ingestion of 50 g sucrose was reduced 20% when coadministered with 60 mL strawberry vinegar. Several years later, Brighenti and colleagues demonstrated in normoglycemic subjects that 20 mL white vinegar (5% acetic acid) as a salad dressing ingredient reduced the glycemic response to a mixed meal (lettuce salad and white bread containing 50 g carbohydrate) by over 30% (P < .05). Salad dressings made from neutralized vinegar, formulated by adding 1.5 g sodium bicarbonate to 20 mL white vinegar, or a salt solution (1.5 g sodium chloride in 20 mL water) did not significantly affect the glycemic response to the mixed meal. Separate placebo-controlled trials have corroborated the meal-time, antiglycemic effects of 20 g vinegar in healthy adults.[49–51]
While compiling a glycemic index (GI) table for 32 common Japanese foods, Sugiyama and colleaguesdocumented that the addition of vinegar or pickled foods to rice (eg, sushi) decreased the GI of rice by 20% to 35%. In these trials, healthy fasted subjects ingested the reference and test foods, each containing 50 g carbohydrate, on random days, and the food GI was calculated using the areas under the 2-hour blood glucose response curves. In the vinegar-containing foods, the amount of acetic acid was estimated to be 0.3-2.3 g, an amount similar to that found in 20 g vinegar (approximately 1 g). Ostman and colleaguesreported that substitution of a pickled cucumber (1.6 g acetic acid) for a fresh cucumber (0 g acetic acid) in a test meal (bread, butter, and yogurt) reduced meal GI by over 30% in healthy subjects.
Recently, the antiglycemic property of vinegar was demonstrated to extend to individuals with marked insulin resistance or type 2 diabetes. In this crossover trial, individuals with insulin resistance (n = 11, fasting insulin concentrations greater than 20 mU/mL) or with diagnosed type 2 diabetes (n = 10) consumed a vinegar test drink (20 g vinegar, 40 g water, 1 tsp saccharine) or placebo immediately before the consumption of a mixed meal (87 g total carbohydrate). In the insulin-resistant subjects, vinegar ingestion reduced postprandial glycemia 64% as compared with placebo values (P = .014) and improved postprandial insulin sensitivity by 34% (P= .01). In individuals with type 2 diabetes, vinegar ingestion was less effective at reducing mealtime glycemia (−17%, P = .149); however, vinegar ingestion was associated with a slight improvement in postprandial insulin sensitivity in these subjects (+19%, P = .07). The lack of a significant effect of vinegar on mealtime glycemia in the type 2 diabetics may be related to the use of venous blood sampling in this trial. Greater within-subject variation in glucose concentrations are noted for venous blood as compared with capillary blood; moreover, the concentration of glucose in venous blood is lower than that in capillary blood. Thus, capillary blood sampling is preferred for determining the glycemic response to food.
The marked antiglycemic effect of vinegar in insulin-resistant subjects is noteworthy and may have important implications. Multicenter trials have demonstrated that treatment with antiglycemic pharmaceuticals (metformin or acarbose) slowed the progression to diabetes in high-risk individuals[56,57]; moreover, because these drugs improved insulin sensitivity, the probability that individuals with impaired glucose tolerance would revert to a normal, glucose-tolerant state over time was increased.
In healthy subjects, Ostman and colleagues demonstrated that acetic acid had a dose-response effect on postprandial glycemia and insulinemia. Subjects consumed white bread (50 g carbohydrate) alone or with 3 portions of vinegar containing 1.1, 1.4, or 1.7 g acetic acid. At 30 minutes post-meal, blood glucose concentrations were significantly reduced by all concentrations of acetic acid as compared with the control value, and a negative linear relationship was calculated between blood glucose concentrations and the acetic acid content of the meal (r = −0.47, P = .001). Subjects were also asked to rate feelings of hunger/satiety on a scale ranging from extreme hunger (−10) to extreme satiety (+10) before meal consumption and at 15-minute intervals after the meal. Bread consumption alone scored the lowest rating of satiety (calculated as area under the curve from time 0-120 minutes). Feelings of satiety increased when vinegar was ingested with the bread, and a linear relationship was observed between satiety and the acetic acid content of the test meals (r = 0.41, P = .004).
In a separate trial, healthy adult women consumed fewer total calories on days that vinegar was ingested at the morning meal. In this trial, which used a blinded, randomized, placebo-controlled, crossover design, fasting participants consumed a test drink (placebo or vinegar) followed by the test meal composed of a buttered bagel and orange juice (87 g carbohydrate). Blood samples were collected for 1 hour after the meal. At the end of testing, participants were allowed to follow their normal activities and eating patterns the remainder of the day, but they were instructed to record food and beverage consumption until bedtime. Vinegar ingestion, as compared with placebo, reduced the 60-minute glucose response to the test meal (−54%, P < .05) and weakly affected later energy consumption (−200 kilocalories, P = .111). Regression analyses indicated that 60-minute glucose responses to test meals explained 11% to 16% of the variance in later energy consumption (P < .05). Thus, vinegar may affect satiety by reducing the meal-time glycemic load. Of 20 studies published between 1977 and 1999, 16 demonstrated that low-glycemic index foods promoted postmeal satiety and/or reduced subsequent hunger.
It is not known how vinegar alters meal-induced glycemia, but several mechanisms have been proposed. Ogawa and colleagues examined the effects of acetic acid and other organic acids on disaccharidase activity in Caco-2 cells. Acetic acid (5 mmol/L) suppressed sucrase, lactase, and maltase activities in concentration- and time-dependent manners as compared with control values, but the other organic acids (eg, citric, succinic, L-maric, and L-lactic acids) did not suppress enzyme activities. Because acetic acid treatment did not affect the de-novo synthesis of the sucrase-isomaltase complex at either the transcriptional or translational levels, the investigators concluded that the suppressive effect of acetic acid likely occurs during the posttranslational processing of the enzyme complex. Of note, the lay literature has long proclaimed that vinegar interferes with starch digestion and should be avoided at meal times.
Several investigations examined whether delayed gastric emptying contributed to the antiglycemic effect of vinegar. Using noninvasive ultrasonography, Brighenti and colleagues did not observe a difference in gastric emptying rates in healthy subjects consuming bread (50 g carbohydrate) in association with acetic acid (ie, vinegar) vs sodium acetate (ie, vinegar neutralized by the addition of sodium bicarbonate); however, a significant difference in post-meal glycemia was noted between treatments with the acetic acid treatment lowering glycemia by 31.4%. In a later study, Liljeberg and Bjorck added paracetamol to the bread test meal to permit indirect measurement of the gastric emptying rate. Compared with reference values, postmeal serum glucose and paracetamol concentrations were reduced significantly when the test meal was consumed with vinegar. The results of this study should be carefully considered, however, because paracetamol levels in blood may be affected by food factors and other gastrointestinal events. In rats fed experimental diets containing the indigestible marker polyethylenglycol and varying concentrations of acetic acid (0, 4, 8, 16 g acetic acid/100 g diet), dietary acetic acid did not alter gastric emptying, the rate of food intake, or glucose absorption.
Safety of Vinegar
Vinegar's use as a condiment and food ingredient spans thousands of years, and perhaps its use can be labeled safe by default. Yet there are rare reports in the literature regarding adverse reactions to vinegar ingestion. Inflammation of the oropharynx and second-degree caustic injury of the esophagus and cardia were observed in a 39-year-old woman who drank 1 tablespoon of rice vinegar in the belief it would dislodge a piece of crab shell from her throat. (The use of vinegar in these situations is a popular Chinese folk remedy.) Her symptoms resolved spontaneously after several days. Esophageal injury by vinegar is likely very rare but deserves notice. Chronic inflammation of the esophagus is a cancer risk; but, as reported previously, vinegar use was inversely related to risk for cancer of the esophagus.
The unintentional aspiration of vinegar has been associated with laryngospasm and subsequent vasovagal syncope that resolved spontaneously. Hypokalemia was observed in a 28-year-old woman who had reportedly consumed approximately 250 mL apple cider vinegar daily for 6 years. Although speculative, the hypokalemia was attributed to elevated potassium excretion related to the bicarbonate load from acetate metabolism.
These complications attributed to vinegar ingestion are isolated occurrences, but with the increased interest in vinegar as adjunct therapy in diabetes, carefully controlled trials to examine potential adverse effects of regular vinegar ingestion are warranted.
For more than 2000 years, vinegar has been used to flavor and preserve foods, heal wounds, fight infections, clean surfaces, and manage diabetes. Although vinegar is highly valued as a culinary agent, some varieties costing $100 per bottle, much scrutiny surrounds its medicinal use. Scientific investigations do not support the use of vinegar as an anti-infective agent, either topically or orally. Evidence linking vinegar use to reduced risk for hypertension and cancer is equivocal. However, many recent scientific investigations have documented that vinegar ingestion reduces the glucose response to a carbohydrate load in healthy adults and in individuals with diabetes. There is also some evidence that vinegar ingestion increases short-term satiety. Future investigations are needed to delineate the mechanism by which vinegar alters postprandial glycemia and to determine whether regular vinegar ingestion favorably influences glycemic control as indicated by reductions in hemoglobin A1c. Vinegar is widely available; it is affordable; and, as a remedy, it is appealing. But whether vinegar is a useful adjunct therapy for individuals with diabetes or prediabetes has yet to be determined.
Carol S. Johnston, Department of Nutrition, Arizona State University, Mesa, Arizona.
Cindy A. Gaas,
VINEGAR AND ITS MOTHER. (from Popular Science magazine, Jan. 1887)
By FREDERIK A. FERNALD.
"SWEET as sugar" and "sour as vinegar" are among the most common comparisons in our language, and the two substances chosen to represent these opposite qualities are popularly deemed as unlike as they can well be. Yet it is one of the marvels of chemistry that the sourest substance with which we are familiar is made from the sweetest. By the action of a ferment, the sugar in some sweet liquid is turned first to alcohol, and the alcohol then changes to acetic acid, which is the acid in vinegar.
In Great Britain, vinegar, until recently, has been manufactured almost entirely from malt—a wort, or sugary solution, weaker than is employed for beer, being first made. Of late years, glucose, cane-sugar, and molasses, have been largely used. British "proof-vinegar" contains 4.6 per cent of anhydrous acid, A notion formerly prevailed that sulphuric acid acted as a preservative to vinegar, and one tenth of one per cent was allowed to be added. Makers continued the practice after they knew that it had no such effect, as it increased the apparent strength of their vinegar at a slight cost. This addition is now an illegal adulteration.
In France, and elsewhere in Europe, the manufacturer starts with an alcoholic liquid, already partly acetified—light wines that have turned sour being generally employed. The French name, vinaigre, from which the English word vinegar is derived, means sour wine. Two sorts are produced—white-wine and red-wine vinegar—the former being generally preferred. These are fine-flavored and somewhat stronger than the malt-vinegar of Great Britain. Six and one half to seven per cent of acid have been found in French vinegars. Sour ale and beer do not yield good vinegar.
In the United States, cider vinegar has long held the preference, and, if the cider has been made from sound, sweet apples, the vinegar has a very agreeable flavor and color. The old-fashioned way which is followed by farmers in making vinegar is to set out-of-doors in the spring a barrel of cider which has become too "hard" and sour to drink, from the sugar partly turning to alcohol and acetic acid. The bung is taken out of the barrel, and the bung-hole is loosely stopped by sticking the neck of a large bottle into it. Such exposure to the air at a warm temperature effects the conversion of the cider to vinegar in three or four months. The change goes on very slowly, because the air can act only on the surface of the liquid, and fresh portions of alcohol are brought to the surface only as the newly formed acid sinks and mingles with the liquid below. The best cider-vinegar is made from new cider, and it is well to cause several fermentations to take place by adding a fresh quantity of cider every two weeks.
Vinegar is chemically a dilute solution of acetic acid, containing minute quantities of fragrant ethers, which give it its odor, and some brownish substance, to which is due its color. Other matters, derived from the liquid from which the vinegar is made, are sometimes accidentally present, as sugar, gum, starch, cream of tartar, and other salts, etc. It usually consists of between ninety-three and ninety-seven per cent of water, the rest being acid, except a fraction of a per cent of solids. The transformation of the sugar in fruit juices or sirups to acetic acid takes place according to the following chemical reactions:
C6H12O6 = 2C2H6O + 2CO2
The bubbles which appear when cider is "working" are carbonic dioxide. In the conversion of alcohol to acetic acid, a subtance called aldehyde is first formed. The oxygen for these changes is taken from the air:
C2H4O + O = C2H4O2
C2H4O + O = C2H4O2
By substantially the same slow process as that still employed in the household was all vinegar obtained from the time of Moses, or earlier, down to 1822. In 1814 Berzelius had found out the chemical composition of acetic acid, and De Saussure that of alcohol; so that, after Doebereiner had discovered that a weak solution of alcohol exposed to the air in contact with platinum-black was converted to acetic acid, he was enabled to set forth the theory on which depends the modern "quick process" of vinegar-making—the method now regularly employed in the vinegar-factories of Europe and America. The essential feature of this process consists in bringing the alcoholic solution into intimate contact with the air by causing it to trickle through a mass of loose material, which effects the acetification in from twenty-four to forty-eight hours. The operation is carried on in wooden tubs, six to ten or more feet high, called generators. Around the sides of the generator, a few inches above the bottom, is a ring of air-holes. Just above the air-holes is a perforated false bottom, and from this nearly to the top the generator is filled with beech-wood shavings, which are closely curled so that they will not crush and prevent the air circulating freely through them. A few inches above the shavings is a wooden head or sieve, perforated with small holes, which serves to distribute the alcoholic liquid, or "wash," evenly over the shavings. Several air-pipes are inserted in the sieve, extending a few inches above and below it. The generator has a cover with a hole in the middle through which the wash is poured in, and the ascending current of air passes out. The vinegar-room is kept at a temperature between 70° and 90° Fahr. A high temperature and large supply of air hasten the operation, but cause loss by the evaporation of the alcohol. If the temperature falls much below 60°, the acetification stops, and putrefaction sets in; while if too little fresh air is supplied, aldehyde, the half-way product mentioned above, instead of being promptly converted to acetic acid, is evaporated and lost. The presence of aldehyde in the air may be detected by its penetrating aroma and by the eyes smarting. The wash must be passed several times through the shavings, in order to effect its complete acetification.
Two kinds of vinegar are sold by grocers in the United States for domestic use—cider-vinegar and white-wine vinegar. Both kinds are made in factories by the process just described. Massachusetts, New York, and some other Eastern States have laws concerning vinegar. In these States the cider-vinegar may be depended on as being really made from cider, for the risk of heavy penalties is incurred by offering anything else under this name. The laws require, also, that all vinegar shall contain four and a half per cent of acetic acid. Cider-vinegar contains a little malic acid, and will give a precipitate with acetate of lead. The absence of the precipitate shows that the sample is not cider-vinegar; but other vinegar, to which malic acid has been added, will, of coiirse, yield the precipitate. Many persons still retain a strong preference for cider-vinegar, but this, like the old preference for feather-beds, is gradually passing away. As rotten apples, and more or less of other kinds of dirt, commonly go into the cider-mill with the sound fruit, and no thorough purification of the product is attempted, not much can be said for home-made cider-vinegar on the score of purity. Many times as much white-wine as cider vinegar is now consumed in the United States, The white-wine vinegar, however, is not made from white wine, as that beverage is not sufficiently abundant in this country to supply the demand of the vinegar-manufacture. Until recently, manufacturers started with whisky, rum, or other alcoholic liquor, but they are now allowed to produce their own spirits. In the East, molasses, and in the West a wort from grain, is first fermented in a vinegar-still—an apparatus having no worm—and a liquor containing fifteen to twenty per cent of alcohol is produced. The liquor is then converted to vinegar in the usual way. This vinegar is perfectly colorless, and the brownish color which the consumer expects in vinegar is given to it by the addition of some harmless substance, as burned sugar, or an infusion of roasted barley-malt. Cider-vinegar has an agreeable flavor, due to the presence of acetic ether and malic acid. Vinegar from well-flavored wines is the most agreeable, as the ethers which give the bouquet to the wine produce a pleasant flavor in the resulting vinegar. Whisky containing fusel-oil yields a pleasant vinegar, as the fusel-oil during the acetification is decomposed into fragrant ethers. Vinegar is flavored artificially by adding to the last wash oil of cloves, or some fragrant ether.
A recipe is given in Ure's "Dictionary," by which it is said that an excellent vinegar for domestic use can be made. To each gallon of a sirup, containing one and a quarter pound of sugar to a gallon of water, is added one quarter of a pint of good yeast. The liquid is kept at a temperature of from 75° to 80° Fahr. for two or three days, and is then racked off from the sediment into the ripening-cask, where one ounce of cream of tartar and one ounce of crushed raisins for each gallon is mixed in. When the vinegar is freed from any sweet taste, it is drawn off clear into bottles and closely corked.
Vinegar should not be kept in metallic vessels except those of silver or perfectly clean copper. Earthenware glazed with oxide of lead (litharge) should never be used, but salt-glazed ware is safe. Vinegar is rarely adulterated with sulphuric acid; and oxalic acid, which is a violent poison, has also been found in it. According to the "United States Dispensatory," if vinegar is evaporated in contact with white sugar, or on white paper, the presence of free sulphuric acid will be indicated by charring. Such acrid substances as red pepper and mustard are sometimes added to vinegar to increase its apparent sharpness. They may be detected by their biting taste after evaporating a portion of the vinegar to a small bulk. Consumers need have little fear of adulterations, however, if their vinegar comes from ordinarily reputable dealers; besides, genuine vinegar can be made more cheaply than any passable imitation. There is more chance of unwholesome vinegar coming into the household in pickles and catchups than when the vinegar is bought alone.
By distillation vinegar is deprived of its coloring and other non-volatile matters. The product is always weaker than the vinegar from which it is derived, as the boiling-point of strong acetic acid is above that of water, and it contains small quantities of alcohol and empyreumatic bodies formed during the operation. Distilled vinegar was formerly used in pharmacy, but dilute acetic acid has now taken its place.
The acetic acid used in the arts is not obtained from the acetification of alcoholic liquors, but from the destructive distillation of wood, generally in the form of sawdust. It is called commercially pyroligne, ous acid, or wood-vinegar, and contains as impurities tar, wood-spirit-etc, which give it an empyreumatic or smoky odor, and which make it superior to other vinegar for preserving meats, pickles, etc. It is purified, and with the addition of coloring and flavoring matters has been sold for culinary use. As the complete purification is an expensive process, there is danger that this vinegar, if sold at a low price, will contain unwholesome substances.
The value of vinegar as a condiment depends on the fact that acetic acid dissolves gelatin, fibrin, and albumen; hence it aids in digesting young meats, fish, lobsters, and hard-boiled eggs. The acid assists also in the conversion of cellulose into sugar, which is the first stage in the digestion of the green leaves used in salads. It is a mistake to use vinegar on beans, for it renders insoluble the legumin, which is their chief nutritive constituent. Oil, pepper, mustard, and a little white wine make the best dressing for beans. It has been proved that some vegetable acid is necessary for the preservation of health, as long continuance in a diet lacking such acids produces scurvy. Vinegar will partly supply this lack, but not wholly, for it will not prevent or cure scurvy, A craving for acid is better satisfied by fruit or acid vegetables. Those young girls who indulge largely in such indigestible articles as pickled limes, cucumbers, etc., would enjoy better health if they should eat instead sour apples, tomatoes, and rhubarb- and cranberry-sauce. The habitual use of vinegar in considerable quantities leads to dyspepsia; the form becomes wasted, on account of insufficient nutrition; and death has been known to result.
Vinegar is used in medicine for its astringent action, being employed locally to check haemorrhage. It is also a refrigerant, for sponging the skin with diluted vinegar has a cooling effect. The heat and pain of sprains and bruises are relieved by applying to the place brown paper soaked in diluted vinegar. This use of vinegar is celebrated in the lines of a certain well-remembered lyric:
"And Jill had the job
To plaster his nob
With vinegar and brown paper."
Aromatic vinegar, called also "Vinegar of the Four Thieves," Marseilles vinegar, or camphorated acetic acid, is strong acetic acid, in which are dissolved certain essential oils, and sometimes camphor. It is said to have been used by a band of four thieves, during a plague at Marseilles, to protect them from infection while plundering the houses and bodies of the dead. It is now used only in smelling-bottles, or vinaigrettes, for cases of fainting, a bit of sponge or some crystals of sulphate of potassium being put into the bottle and moistened with the liquid. Aromatic vinegar is very fragrant and volatile, and must be kept in closely stoppered bottles. A variety of recipes for it are given: that especially recommended in the "United States Dispensatory" is one and a half fluid drachm best oil of rose-geranium, fifteen minims oil of cloves, and four fluid ounces glacial acetic acid.
The tough, leathery substance, commonly called "mother," which forms in vinegar, is one of the many fungi whose spores float in the air, settle as dust on exposed objects, and fall into exposed liquids, ready to grow into a bulky plant when conditions favor. The exact position of the vinegar-plant among the fungi has not been settled. Turpin, Berkeley, and others, say that it is the abnormally developed mycelium, or vegetative part, of Penicillium glaucum, of which common mold is the reproductive part. Pasteur and others maintain that it is a distinct species, calling it by the name Mycoderma aceti, and state that common mold frequently grows on its surface. Under the microscope it has been found to exhibit two forms—the minute, rounded particles called micrococci, and the rod-like forms known as bacilli. The vinegar-plant develops during the process of acetification, and its presence tends to accelerate the operation. Manufacturers get rid of it as soon as possible, for it interferes with the flow of the vinegar through their apparatus. It grows on the surface of the vinegar, and if not disturbed will cover the whole surface, conforming to the shape of the vessel. It has been known to reach a thickness of half an inch. The mycoderm seems to have an oxidizing action, and so, when the alcohol in the liquid fails, it probably grows at the expense of the acetic acid, converting it to carbonic dioxide and water. There is a popular notion that the presence of "mother" shows that the vinegar is made from cider, and is of good quality, but the vinegar-plant appears also in vinegar made from molasses, and it is really as undesirable in vinegar as mold on bread.
The little, wriggling creatures which swarm in some vinegars have been credited by uneducated persons with being the "life" of the vinegar. In one sense they are, but their presence is in no way beneficial. These vinegar-eels (Anguillula accti), as they are called, are developed in most fruits, and hence readily find their way into vinegar made from fruit-juices. Vinegar which contains them must contain also as impurity some mucilaginous or albuminous matter, or the eels would have no food and could not exist. They need air also, and they have been observed engaged in a curious struggle with the mycoderm on the surface. The plant tends to prevent their obtaining the requisite supply of air, and the eels were seen combining their efforts to submerge it. They may be killed by heating the vinegar to 128° Fahr., or by adding boracic acid. Vinegar when long kept, especially if exposed to the air, putrefies and becomes ropy, losing its acidity, and acquiring an unpleasant smell; the presence of the vinegar-plant, vinegar-eels, or other foreign substances, is liable to induce putrefaction, especially if the vinegar is weak.
Posted by Blog Staff at 3:20 PM