- Sweetness: Sugar content can be determined by chemical analysis for total and reducing sugars or for individual sugars (e.g., yellow pitaya: Dag and Mizrahi, 2005). Total soluble solids can be used as a proxy measure of sugar content because sugars are the predominant component of fruit juice soluble solids. This parameter is measured with a fruit refractometer.
- Sourness (acidity): pH of extracted juice can be quantified with a pH meter or pH indicator paper. Total titratable acidity can be derived by titrating a specific volume of the extracted juice with 0.1 M NaOH to pH 8.1, then calculating titratable acidity as citric, malic, or tartaric acid, depending on which organic acid is dominant in the commodity.
- Astringency is quantified by taste test or by measuring the solubility of tannin or its degree of polymerization.
- Bitterness is quantified by taste test or by measuring alkaloids or the specific glucosides responsible for bitter taste.
- Aroma (odour) is quantified by use of a human sensory panel in combination with identifying the specific volatile components responsible for the aroma of the fruit.
- A comprehensive sensory evaluation can be used to characterize the combined sensory characteristics (sweetness, sourness, astringency, bitterness, overall flavour intensity) of the fruit.