Читать книгу Food Chemistry - Dennis D. Miller - Страница 15
1.2.1 Acids
ОглавлениеAcids serve a variety of functions in foods including flavor enhancement, control of microbial growth, protein coagulation, emulsification, control of browning, buffering action, and metal chelation (to control lipid oxidation). All acids have a sour taste but different acids produce distinctively different sour flavors. Thus, it is not enough to simply add any acid when attempting to produce a characteristic sour flavor in a food. Table 1.1 gives structures and pK values of some common food acids.
Table 1.1 Acids common in foods: structures and pKa values.
| Substance | Structure | pKa | Food found in |
|---|---|---|---|
| Acetic acid | pK = 4.75 | Vinegar, figs | |
| Adipic acid | pK1 = 4.43 pK2 = 5.62 | Beets | |
| Butyric acid | pK = 4.82 | Cheese, butter | |
| Citric acid | pK1 = 3.06 pK2 = 4.74 pK3 = 5.40 | Oranges, lemons, apricots, tomatoes | |
| Lactic acid | pK = 3.83 | Yogurt, buttermilk, cheese, beer | |
| Malic acid | pK1 = 3.40 pK2 = 5.05 | Apples, apricots, grapes, oranges, tomatoes | |
| Oxalic acid | pK1 = 1.27 pK2 = 4.27 | Spinach, potatoes, tomatoes | |
| Phosphoric acid | pK1 = 2.12 pK2 = 7.21 pK3 = 12.32 | Tomatoes, acidulant used in soft drinks | |
| Tartaric acid | pK1 = 2.98 pK2 = 4.34 | Grapes | |
| Sodium hydrogen sulfate or sodium acid sulfate | pK = 1.99 | Acidulant. Lowers pH without imparting acid taste. May be added to process water to enhance chlorine activity |
