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2008年11月25日 · Brix/acid ratio is considered the best objective measurement that reflects the consumer acceptability of juices [34].
The empirical Brix/acid ratio, found by dividing the acid-corrected and temperature-corrected Brix by the % titratable acidity w/w as citric acid (B/A ratio), is one of the most commonly used indicators of juice quality as well as fruit maturity.
- Dan Kimball
- 1991
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2008年11月25日 · The applicability of objective measurements such as soluble solids concentration ( Brix), acid contents (titratable acidity) and Brix/acid ratio of Crimson Seedless table grapes were evaluated as predictors of quality in terms of consumer acceptability.
The empirical Brix / acid ratio, found by dividing the acid-corrected and tem perature-corrected Brix by the % titratable acidity w / w as citric acid (B / A ratio), is one of the most commonly used indicators of juice quality as well as fruit maturity. In California, the fruit harvested for the fresh fruit markets needs.
- Dan Kimball
- 1991
- Overview and Principle
- General Considerations
- Preparation of Reagents
- Sample Analysis
- Calculation of Titratable Acidity
- Acid Content in Food
- Volatile Acidity
- Other Methods
The titratable acidity measures the total acid concentration in a food. Food acids are usually organic acids, with citric, malic, lactic, tartaric, and acetic acids being the most common. However, inorganic acids such as phosphoric and carbonic (arising from carbon dioxide in solution) acids often play an important and even predominant role in food...
Many food properties correlate better with pH than with acid concentration. The pH is also used to determine the endpoint of an acid-base titration. The pH determination can be achieved directly with a pH meter, but more commonly using a pH-sensitive dye. In some cases, the way pH changes during titration can lead to subtle problems. Some backgroun...
4.3.1 Standard Alkali
Sodium hydroxide (NaOH) is the most commonly used base in titratable acidity determinations. In some ways, it appears to be a poor candidate for a standard base. Reagent grade NaOH is very hygroscopic and often contains significant quantities of insoluble sodium carbonate (Na2CO3). Consequently, the normality of working solutions is not precise, so each new batch of NaOH must be standardized against an acid of known normality. However, economy, availability, and long tradition of use for NaOH...
4.3.2 Standard Acid
The impurities and hygroscopic nature of NaOH make it unsuitable as a primary standard. Therefore, NaOH titrating solutions must be standardized against a standard acid. Potassium acid phthalate(KHP) is commonly used for this purpose. KHP’s single ionizable hydrogen (pKa= 5.4) provides very little buffering at pH 8.2. It can be manufactured in very pure form, it is relatively nonhygroscopic, and it can be dried at 120 °C without decomposition or volatilization. Its high molecular weight also...
A number of official methods exist for determining titratable acidity in various foods . However, determining titratable acidity on most samples is relatively routine, and various procedures share many common steps. An aliquot of sample (often 10 mL) is titrated with a standard alkali solution (often 0.1 NNaOH) to a phenolphthalein endpoint. Potent...
In general chemistry, acid strength is frequently reported in normality (equivalents per liter) and can be calculated using Eq. 22.1. However, food acids are usually reported as percent of total sample weight. Thus, the equation for titratable acidity is as follows: where: 1. N= normality of titrant, usually NaOH (mEq/mL) 2. V= volume of titrant (m...
Most foods are as chemically complex as life itself. As such, they contain the full complement of Krebs cycle acids (and their derivatives), fatty acids, and amino acids. Theoretically, all of these contribute to titratable acidity. Routine titration cannot differentiate between individual acids. Therefore, titratable acidity is usually stated in t...
In acetic acid fermentations, it is sometimes desirable to know how much acidity comes from the acetic acid and how much is contributed naturally by other acids in the product. This can be achieved by first performing an initial titration to measure titratable acidity as an indicator of total acidity. The acetic acid is then boiled off, the solutio...
High-performance liquid chromatography (HPLC) (see Chap. 13) and electrochemistry both have been used to measure acids in food samples. Both methods allow identification of specific acids. HPLC uses refractive index, ultraviolet, or for some acids electrochemical detection. Ascorbic acid has a strong electrochemical signature and significant absorb...
- George D. Sadler, Patricia A. Murphy
- 2010
Brix/acid ratio was found to be the best objective measurement that reflected the consumer acceptability and can be used as a reliable tool to determine the optimum harvesting stage of Crimson Seedless table grapes.
The empirical Brix/acid ratio, found by dividing the acid-corrected and temperature-corrected Brix by the % titratable acidity w/w as citric acid (B/A ratio), is one of the most commonly used indicators of juice quality as well as fruit maturity.
