Understanding and Identifying Ranges for Critical Parameters of Orange Juice Concentrate during Drying by Using Solar Assisted Pervaporation (SAP) Fruit Preservation Technique

Abstract

Solar Assisted Pervaporation (SAP) is a novel technique of preservation that combines the concept of membrane separation and the use of solar energy. The method uses a ‘breathable pouch’ with an active layer of a food-grade hydrophilic membrane.

The aim of this study was to understand how different drying temperatures (50oC and 60oC), air exclusion treatment (with and without vacuum) and type of container (membrane pouch SAP and open dish) affect the chemical reactions during drying and the physicochemical characteristics of the mandarin juice concentrates and its reconstituted product. The properties of water activity, moisture content, oBrix, pH, vitamin C and colour of the concentrates and the rehydrated samples were measured. The drying curves, convective mass transfer coefficients and sorption isotherms of the concentrates were also examined.

SAP technique resulted in a stable mandarin concentrate with water activity between 0.60-0.65, total soluble solids between 80 to 83 oBrix and moisture content between 20-23% (dry basis). The drying time with the SAP technique was 22 hours at 50oC and 16 hours at 60oC which were longer compared to the samples in open dish trays. In agreement with the drying time, the mass evaporation flux and convective mass transfer coefficient of the pouch samples were also lower compared to the samples in open dish trays. It is likely the additional barrier from the membrane that inhibited the evaporation process. The air exclusion treatment and different type of container appeared to be the most important factors in the reduction ascorbic acid content while different drying temperatures affected the colour of the concentrates and rehydrated samples.

Popular Abstract

Study on mandarin concentrates production process by using an inexpensive on-site fruit preservation technique

A stable mandarin concentrate was obtained by using a new drying technique which combines a membrane separation technique and the use of renewable solar energy. The characteristics of the rehydrated juice resembled the fresh mandarin juice.

The US Government estimates that there is 25-40% fruit post-harvest loss due to spoilage in Mozambique. This loss also means income loss for the farmers. Furthermore, sophisticated facilities to preserve the fruits, such as pasteurisation, need a high amount of capital to be built and therefore, not a practical solution for small scale farmers. Solar Assisted Pervaporation (SAP) technique tries to answer the problem by providing an inexpensive and robust technique to prolong the shelf life of the fruits which leads to higher income for the farmers.

SAP technique uses a ‘breathable’ membrane pouch and it is combined with solar energy to increase the efficiency of the drying process. As a new technique, there is still ample room for exploration of SAP. One of the most important things is to compare the characteristics of the fruit concentrate and the rehydrated juice if the drying process is performed with and without the membrane pouch.

SAP offers a more hygienic way of drying and protection of the product from the contamination. However, it was desired to know whether the SAP method could provide more advantage regarding quality preservation compared to the conventional drying method in open dish trays. In this project, the drying characteristics and the chemical reactions occurring during the drying were studied. The loss of vitamin C and the change of colour of the concentrate and the rehydrated juice were measured. The vitamin C content and colour represent the most important quality parameters to deliver a high-quality product to the consumers.
By knowing the drying characteristics and also identifying the possible chemical reactions take place during the preservation process, an optimal product can be designed. The drying characteristics provide critical information which can be used to predict the drying time if a different drying temperature, a different dimension of the membrane pouch or a different volume of the sample are used. The identification of chemical reactions provides insight on how harsh the drying process impact the nutrition content so that preliminary actions (e.g. fortification, blanching, etc.) can be estimated.

Author:
Ferawati Ferawati

Original Title:
Understanding and Identifying Ranges for Critical Parameters of Orange Juice Concentrate during Drying by Using Solar Assisted Pervaporation (SAP) Fruit Preservation Technique

• author: Ferawati, Ferawati
• supervisor: Ingegerd Sjöholm; Randi Phinney
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLTM01 20161
• year: 2016
• type: H2 - Master's Degree (Two Years)
• subject: Agriculture and Food Sciences
• keywords: water activity, pouch, concentrate, solar assisted pervaporation, mandarin, ascorbic acid, colour, food engineering, livsmedelsteknik
• language: English
• id: 8881218
• date added to LUP: 2016-06-27 08:43:27
• date last changed: 2016-06-27 08:43:27