Thermal properties of Corinthian currant pastes as affected by storage

Abstract

Currant paste made of Corinthian currants, a variety of raisins (Vitis vinifera, var. apyrena), is a highly nutritious product containing low-molecular weight sugars, whose physical state affects their stability. Thermal properties (glass transition temperature, melting temperature, and melting enthalpy) of Corinthian currant pastes were investigated as a function of relative humidity and storage temperature. Glycerol was added to currant paste at levels 0%–15% by weight. A simple power model was developed for thermal properties prediction. Furthermore, the sorption characteristics of currant paste samples were studied and were well described by the five-parameter GAB sorption model. Water and glycerol acted as plasticizers depressing the thermal properties of currant paste samples. The increase in the storage temperature resulted in an increase in glass transition and melting temperatures, while melting enthalpy decreased. The selection of relative humidity and storage temperature is critical for the maintenance of desirable quality characteristics of Corinthian currant pastes. Practical applications Today's consumer demand for plant-based products has driven the food manufacturers to the development of novel plant-based products. Air-dried fruits are high nutritional foods and an excellent source of functional and nutraceutical ingredients. The development and production of a paste from Corinthian currants is a novel food that meets the above purposes. The phase state of the product ingredients, amorphous and crystalline regions, is critical for product quality assessment and storage stability. The contribution of this research in these terms relies on the investigation of the thermal properties of these products, such as glass transition temperature, melting temperature and melting enthalpy, and the development of a simple power model for properties prediction. Based on relative humidity and storage temperature, it could be used in determining the best storage conditions of Corinthian currant paste to keep its desirable quality characteristics, while it can be applied to similar products.