Effect of different Pre-treatments on the physicochemical properties of Freeze-Dried Ananas comosus L

Abstract

Abstract Pineapple is high in vitamins, minerals, antioxidants and it is the major source of bromelain enzyme which is a strong anti-inflammatory and anti-cancer compound. Freeze drying technique has been used to preserve the nutrients in fruits by using the principle of sublimation which dries the materials at very low temperature and pressure. However, the physicochemical properties of its product may deteriorate without suitable pre-treatment. The present study aims to study the effect of different pre-treatment techniques on the changes of physicochemical properties of pineapple slices when drying in freeze-dryer. Four pre-treatments techniques were applied such as hot blanching (HB), hot syrup (SB), soaking in ascorbic acid (AA) and citric acid (CA) to the physical properties, antioxidant activity and bromelain content of the freeze-dried pineapple slices were studied and compared to the non-treated (C) sample. The results showed that the SB pineapple has significantly higher moisture content than the untreated dried pineapple. While sample soaked in CA has the lowest pH value and all pre-treatment has higher total soluble sugar (TSS) value than the control pineapple. For colour determination, a significant (P