Acetic acid turns sour into salubrious

The five known tastes impart a gustatory array of pleasure and discomfort. Sour, a signature flavour of many fermented foods, is mediated by acids, often organic (comprised of molecules that contain at least one carbon atom). One acid that is gaining accolades is acetic acid, the principal acidic component in vinegar. Acetic acid is a more potent stimulator of sour taste receptors than hydrochloric acid, when both are at the same pH.1 It also is produced de novo in cellular metabolism.

Several Europe-based feeding studies in humans have shown that consumption of fermented breads, or meals comprised of bread plus vinegar, produces blunted glycaemic responses.2,3 In one study, white wheat bread (crust removed) was consumed with cheese and with or without white wine vinegar (20g) in single test meals randomly ordered.4 The meal accompanied by white vinegar was marked by significantly lower glycaemic and insulinaemic responses, which was ascribed, in part, to reduced rates of absorption. Studies conducted in Japan with common Japanese foods revealed similar results, namely foods where vinegar was added — for example, sushi rice — exhibited reduced glycaemic excursions.5

A more recent study examined the effect of vinegar upon blood glucose and insulin dynamics in persons with insulin resistance and type 2 diabetes.6 In this study, the subjects consumed a saccharin-sweetened solution of apple cider vinegar (20g) or a placebo drink, followed by a bagel, butter and orange juice meal. Among the subjects with insulin resistance, the vinegar solution fostered a 34 per cent improvement in whole body insulin sensitivity and depression in both glycaemic and insulinaemic excursions, relative to placebo. Only modest effects were seen in the control group and type 2 diabetics.

A novel realm of vinegar applications extends into vascular function. Depending upon the starting biomass, the chemoprofile of a specific vinegar can vary markedly. Studies performed with animals that spontaneously manifest hypertension have displayed a robust lowering of blood pressure by the addition of either acetic acid or vinegar to the diets.7

Additional animal studies with a combination of red wine vinegar and grape juice have yielded antihypertensive results, with pilot data in humans corroborating these findings.8 The most recent investigations with this combination have confirmed a modest inhibitory effect upon angiotensin-converting enzyme activity in vivo and relaxation of blood-vessel tension (vasodilator effect),9 partly mediated through nitric oxide.10

Vinegar shares a ?chemo-heritage? with wine in that the starting biomass can dictate the chemoprofile of the finished ?beverage.? Vinegars made from grape products contain appreciable amounts of phenolic constituents and, like their white and red progenitors, vary depending upon the colour.11 Oxygen Radical Absor-bance Capacity measurements (an in vitro assessment of antioxidant action, but has yet to be closely correlated to in vivo antioxidant activity) of various grape derivatives found certain red wine vinegars (from cabernet sauvignon and sherry wines) to approach the ORAC value and total phenolic content of certain white and red grape juices.12 The next challenge is the integration of vinegar/acetic acid into foods and beverages with high hedonic profiles.

Anthony Almada, MSc, is president and chief scientific officer of IMAGINutrition Inc. Respond: [email protected]

1. Ugawa S, et al. Receptor that leaves a sour taste in the mouth. Nature 1998; 395:555-6.
2. Liljeberg HGM, et al. Sourdough fermentation or addition of organic acids or corresponding salts to bread improves nutritional properties of starch in healthy humans. J Nutr 1995; 125:1503-11.
3. Liljeberg HGM, Bj?rck IME. Delayed gastric emptying rate as a potential mechanism for lowered glycemia after eating sourdough bread: studies in humans and rats using test products with added organic acids or an organic salt. Am J Clin Nutr 1996; 56:389-94.
4. Liljeberg H, Bj?rck I. Delayed gastric emptying rate may explain improved glycaemia in healthy subjects to a starchy meal with added vinegar. Eur J Clin Nutr 1998; 52:368-71.
5. Sugiyama M, et al. Glycemic index of single and mixed meal foods among common Japanese foods with white rice as a reference food. Eur J Clin Nutr 2003; 57:743?52.
6. Johnston CS, et al. Vinegar improves insulin sensitivity to a high-carbohydrate meal in subjects with insulin resistance or type 2 diabetes. Diabetes Care 2004; 27:281-2.
7. Kondo S, et al. Antihypertensive effects of acetic acid and vinegar on spontaneously hypertensive rats. Biosci Biotechnol Biochem 2001; 65:2690-4.
8. Sugiyama A, et al. Acute cardiovascular effects of a new beverage made of wine vinegar and grape juice, assessed using an in vivo rat. Nutr Res 2003; 23:1291?6.
9. Honsho S, et al. A red wine vinegar beverage can inhibit the renin-angiotensin system: experimental evidence in vivo. Biol Pharm Bull 2005; in press.
10. Takahara A, et al. The endothelium-dependent vasodilator action of a new beverage made of red wine vinegar and grape juice. Biol Pharm Bull 2005; 28:754-6.
11. Alonso AM, et al. Study of the antioxidant power of brandies and vinegars derived from sherry wines and correlation with their content in polyphenols. Food Res Int 2004; 37:715-21.
12. D?valos A, et al. Antioxidant properties of commercial grape juices and vinegars. doi:10.1016/j.foodchem.2004.09.030.

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