Tropical Tuber Crops

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When, where and how the research project was conceptualized ?

The tropical tuber crops play a dual role in being a source of food as well as industrial raw material. However, they have not received enough importance due to various factors. The main factors are that the tubers are considered poor mans crop and there is little awareness of the variability available in the starch properties of these crops. Again the knowledge about the innumerable products, which can be produced from starch, has been scanty. So all these aspects needed to be addressed to enhance the importance of these crops and research projects covering food and industrial applications of these neglected crops were formulated and carried out. In addition, an ad-hoc project on minor tuber starches was undertaken in collaboration with RRL, Trivandrum. Similar work was carried out during my advanced training at the Food Science department of Nottingham University, and Natural Resources Institute, UK and later on at Food technology department of Lund University, Sweden during the Sabbatical leave.

For use of cassava as food, the cooking quality is of utmost importance and success of any new variety depends on the acceptability by the consumers. Previously only yield was taken into consideration, but subsequently the importance of quality was realized and hence was accepted as an essential criterion for variety release. The experience gained from analyses of a large number of samples was useful in formulating detailed studies on factors responsible for good cooking quality of cassava tubers.

The idea of starch data bank which provides exhaustive data on different starches and also starch bank having a collection pf natural starches with different characteristics has been mooted and CTCRI having the most abundant collection of root crops could best serve as the centre for this activity. Hence a detailed study of the properties of all the tropical tuber starches was carried out keeping in view effect of varietals variation and environmental factors on the properties.

Since there has been increasing stress on value addition, processes for a number of products based on the starches were developed which could in future make these crops highly sought after. In view of the increasing demand for environment -friendly products development of technologies for such products is highly relevant to the present day context.

When, where and how it was conducted ?

The work was carried out over a period of nearly 25 years and most of the work was conducted at the Crop Utilization and Biotechnology division of CTCRI, Trivandrum. Part of the work was also carried out at Food Science department, University of Nottingham, NRI, UK ( 6 months ) and at Food Technology department, Lund University, Sweden (11 months).

In view of the importance of the tuber crops in food and industry, the work on the cooking quality of cassava tubers, starch properties and product development was taken up. First of all infrastructural facilities were built up to carry out the work. Visits were made to ATIRA, Ahmedabad, CFTRI, Mysore etc. and discussions with scientists and technologists working on starches and related compounds were carried out. Based on the ideas thus generated, equipments like Brabender Viscograph, IR and UV Visible spectrophotometers were procured in addition to common laboratory equipments. Books and journals related to starch and food were added to the institute library. The cooking quality studies were carried out using the tubers from varieties available in the Institute. The studies on cassava starch were helpful in my getting deputed to UK . I carried with me a number of samples of starch and flour from different varieties and used the facilities available there to analyse them. DSC studies were carried out in detail on the starches. I also made use of this opportunity to get acquainted with Deer Viscometer and Rheogonimeter. Methodology for Gel Permeation chromatographic analysis of debranched starch samples and use of Coulter Counter for granule size measurement were the other techniques which I learned there. A lot of data on starch properties of tuber crops was generated and published in International journals. Meanwhile a project on the minor starches was undertaken in collaboration with Dr. Raja of RRL, Trivandrum financed by ICAR-Cess Fund. When I got an offer for Sabbatical work at Lund University to work with Prof Eliasson, an authority on starch, I carried with me the different tuber starch samples and studied their thermal properties using the highly advanced Modulated DSC technique and generated voluminous data on the tuber starches, especially interaction with lipids and surfactants. Similarly detailed studies on rheological properties of the starches were carried out and this is the first time that exhaustive work on rheology of starches has been carried out using a Bohlin Rheometer, which provides a wealth of data on starch rheology. Since value addition is of utmost importance, various products were developed from the tuber crops and their starches, which can have application in food and industry. These include food items, adhesives for different applications, fructose syrup and starch derivatives having varying physicochemical and functional properties. The products and technologies were demonstrated at different exhibitions, training classes and visitors to the Institute for possible adoption. Thus the results presented are based on a concerted study carried out over a long period and covers basic and applied aspects.

What were the Socio- economic, Technological and Scientific Relevance and Priority of the research project ?

The tuber crops are considered poor mans crop in spite of the fact that they provide food having high calorific and also starch useful in industry. Mostly marginal and small farmers cultivate them. Except cassava they do not have any industrial base at present. The lure of cash crops and easy availability of cereals and changing food habits are further threatening the survival of these crops. The crops can grow well under adverse conditions (as recently proved by the experience of the farmers during the Orissa Cyclone a few years back when only the tuber crops survived) and so it is necessary that these crops are retained in the cropping schedule. This is possible only by value addition to a good extent so that the farmers get good profit from these crops. The crops can be very suitable for cultivation in North Eastern belts and tribal areas of the country, where the major use will be as food and hence good cooking quality and development of new simple foods need priority. These important aspects have been duly addressed.

Except cassava other tuber crops are not used in India for the extraction of starch mainly due to the difficulty in extraction of pure starch from them. If starch can be commercially extracted from the other tuber crops also, they will have higher demand and the farmers will be eager to cultivate the crops. The knowledge of starch properties of the tuber crops is scanty and hence the awareness of their potential applications is limited. So the studies on the tuber starches are very pertinent and can throw open new vistas of their applications. In addition to providing basic knowledge, the studies can throw light on the most desired characteristics of starch, which may be achieved by use of biotechnological tools. They can also substitute the chemically modified starches, which may create health problems.

Product and process developments are becoming very important in the present day context in view of the necessity to be competitive in the world economic scene, Value added food and industrial products with domestic and export potential need to be developed and has also been given high priority in the work. The demand for environmentally friendly products and food items suited to the health-conscious public have also been given due consideration.

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