Brix/acid ratio

Several postharvest treatments to citrus fruits have been tested in an effort to improve the quality of the extracted juice. Bruemmer and Roe subjected citrus fruits to anaerobic conditions for periods of 20 to 32 hours at 32.2 to 43°C (228, 229). This treatment reduced the titratable acidity and increased the Brix-acid ratio by about 10%. The decrease in acidity was accompanied, however, by a 20-fold increase in ethanol (229). Since the soluble solids-acid ratio is a major criterion of citrus juice quality, this procedure, if perfected, could allow earlier harvesting of fruit and a more consistent supply of fruit during the processing season. Bitterness of products from navel oranges, lemons, and grapefruit is related to limonin content. A 3-hour treatment of fruit with 20 ul ethylene/1 of air lowered the limonin content, reduced bitterness, and the juice was judged more palatable than juice from untreated fruit (230). 

Composition. Scientific data concerning liquids washed with water from orange juice finisher pulp was first published by Olsen et al. (30). They studied Brix/acid ratios, sucrose, reducing sugars, pH, pectic constituents, turbidity, pulp content, ascorbic acid, viscosity, and flavonoid content of experimental and commercial samples. Characterization of pulp-wash continued with publication of quality data (31), examination of pectic substances (32), microbiology (33), and comparison of pulp-wash with orange concentrate (34). 

Grapes are picked at optimum °Brix/acid ratio to ensure that the fruit has the best quality characteristics as to sugar, acid, and, in the case of black grapes, color. The intent is to receive the fruit in the best possible condition. 

Samples of the sugars being removed are cooled to 20°C. and tested for density by a sugar Brix spindle., Analysis of these solutions shows that the reducing sugar content of the solutions is 60 to 70% of the concentration shown by the Brix spindle. If the hydrolysis of hemicellulose is not complete, the ratio of reducing sugar to Brix will be low and will indicate that insufficient acid has been used. 

After sweetness, the second most important feature of a soft drink is acidity and the balance of the sweetness to acidity (sourness), commonly called the Brix to acid ratio. An acceptable range for this ratio is often laid down in juice specifications. For European tastes in orange juice, a Brix to acid ratio might be set around 15 and 16. 

There are also certain other factors associated with flavor grade, namely minimum and maximum degrees Brix to % acid ratio and oil content requirements. Should there be a question as to the flavor by either the inspector or the plant personnel, the inspector will submit a sample to the USDA Processed Products Branch area office for another evaluation. 

Wild apricot (Prunus armenica L.) grows naturally in hilly areas of northern India. It is highly acidic, fibrous, and low in TSS, and, thus, not utilized commercially. Preparation and evaluation of a vermouth from its fruit was undertaken (Abrol, 2009). Vermouths at different sugar (8,10, and 12 °Brix), alcohol (15%, 17%, and 19%), and spices levels (2.5% and 5%) were prepared. Those used in extract preparation are shown in Plate 8.1. The base wine was prepared from crushed fruit, adjusted to 24 °Brix, and diluted in a 1 2 ratio with water. To this mixture was added 200 ppm sulfur dioxide, 0.1% diammonium hydrogen phosphate (DAHP), and 0.5% pectinase enzyme. A 24-h active yeast culture initiated fermentation. The procedure is illustrated in Fig. 8.4. A maturation period of 6 months improved the quality of the vermouth. 

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