Thesis subject

Drying Fruits

Topic 1. Integrated Optimization of Product and Process Design of Dried Tropical Fruit and Its Products for Different Health Attributes

The quality perception of dehydrated and/or dried tropical fruit products by consumers differs from one type to another end product, such as dried fruit as a single product, mixed with nuts or breakfast cereals, within snack or confectionery.
An integrated optimization of product and process design of dried fruit and its products for different health attributes will be done through several experimental research and modelling, as followed:
1. A mathematical modelling to derive kinetic parameters as function of T and aw in order to optimize the drying processes of fruit.
2. Study on product quality changes of dehydrated and/or dried fruit products during
proper storage.
3. The effect of selected packaging techniques for some dried fruit products (i.e. Modified Atmosphere Packaging) on the alteration of key quality variables of dehydrated and/or dried fruit products during proper storage.

For more information please contact Ita Sulistyawati.

Topic 2. Health-promoting compounds (Withanolides) in Cape Gooseberry (Physalis peruviana L.) fruit.

With anolides are a group of naturally occurring steroidal lactones which are mainly produced by the solonaceae family. Their name comes from the genera withania, that initially was considered to be the unique source. There is evidence, however, that the genus physalis also contains withanolides. There is high interest in these biocompounds since there is studies about their pharmacological activities, such as antitumor, anti-inflammatory, hepatoprotective, immunomodulatory activities, among others. Studies have been done on the whole plant of physalis peruviana L. including fruit, suggesting that cape gooseberry also contains of withanolides, but the withanolide content of the fruits is still unknown. A study to assess the contents of withanolides in cape gooseberry fruit and its processed product is needed to find out if this fruit and products have the special health promoting properties related to withanolides.

Set up the analytical method to identify and quantify withanolide. Apply this method to obtain the withanolide profile in cape gooseberry fruits and the effect of processing on this profile.

For more information please contact Ruud Verkerk.

Topic 3. Effect of Processing Condition, Maturity Stages, Matrix Modification and The Use of Ternary Compounds on The Quality of Osmotic Dehydrated  and/or Dried Tropical Fruit.

As a healthy product but highly perishable commodity, diverse technology has been applied to extend shelf life of fruit. From the various existing processed fruit products, dried/dehydrated fruits are getting substantial attention, and recently the availability of those products in the market has increased considerably. Dried fruit is higher in energy per serving than fresh, canned, frozen fruit and most fruit juices. Their high content of dietary fibre (1.9-12.4 g/100 g) contribute to more than 7.5% of the US daily value, 25 g  per serving (40 g). Most of them contain vitamins (especially vitamin A and C) and a wide range of phytochemicals.

The use of a combination of osmotic dehydration and heated drying techniques resulted in higher quality shelf-stable products to many type of dried fruits, compared to the application of only one of them. Among numerous attempts to improve the efficiency of osmotic dehydration process, the use of polysaccharide based-edible coating and food additives especially texture modifying agents (i.e. cell wall-modifying enzyme, Calcium (Ca) salts, phenolic compounds) shown good results.

Some of the research topics which involve experimental work in the laboratory might be, as followed:
1.    Study on the effect of processing condition and maturity stages to the quality of dried fruit and its products on the physico-mechanical and chemical properties
2.    Study on the behaviour of some important cell wall-modifying enzymes during the process of osmotic dehydration and/or drying of fruit as well as during storage.
3.    Study on the effect of several process variables (incl. type and concentration of polysaccharides-based edible coating and texture modifying agents) to the quality of dried fruit and its products on the physico-mechanical and chemical properties.
4.    Study on the effect of ternary compounds (sugars, several types of Ca-salts and weak acids) on the quality of osmotically dehydrated and/or dried fruit, especially toward the flavour release and colour degradation. This research might involve sensory evaluation.
Response Surface Methodology (RSM) will be applied to optimize important factors to have quality osmotically dehydrated and/or dried fruit according to their destined products.

For more information please contact Ita Sulistyawati.