Determination of Total Soluble Solids TSS

Total soluble solids (TSS) is a measurement of the sugar, organic acid and other soluble components in the juice of the apricot. TSS is useful as an indicator of maturity in conjunction with firmness. It is measured in terms of percent pure sucrose because sucrose is the major constituent of apricot fruit juice. TSS can be determined using a Brix hydrometer (measurement of specific gravity), or an Abbe or hand refractometer (measurement of the refractive index) (Childers and Zutter 1983). 

If a bulk sample of juice is to be determined, a hydrometer is recommended. For smaller samples, the larger Abbe can be used for precise determination in a laboratory or the hand model can be used in the field. All instruments give readings in terms of °Brix calibrated as percent sucrose at 20 °C (Soide 1985). It must be remembered that there are other soluble solids which may alter the refraction of light, present in the juice (Byrne et al. 1991). However, because sucrose is the major constituent of the total soluble solids, readings give a reasonable reflection of sweetness (Kramer 1973). 

Total soluble solid content of apricots ranges from 5-30°Brix depending on the variety and maturity of the fruit (Mehlenbacher et al. 1983). 

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