Comparison of Physicochemical and Functional Properties of Cassava Starch Extracted from Fresh Root and Dry Chips
| Main Authors: | , |
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| Format: | Article |
| Language: | English Slovak |
| ISSN: | ISSN 0038-9056 |
| Online Access: | http://www.viks.sk/chk/star_7_03_287_296.doc |
| Abstract: | SUMARRIES. Starch was extracted from dry chips of three varieties of cassava using wet milling and dry milling methods. The physicochemical and functional properties were compared with those from fresh root. The starch obtained exhibited lower peak viscosities, breakdowns and setbacks, and higher pasting and peak temperatures than that from fresh root. Most thermal properties (onset and peak temperatures of gelatinization and ret-rogradation; conclusion temperatures, enthalpies and peak height indices of retrogra-dation; and degree of retrogradation) were found to be higher than those of fresh-root starch. Moreover, swelling power, paste clarity and freeze-thaw stability of the former were inferior to those of the latter. Both types of starches exhibited increased rate of syneresis with increase in freeze-thaw cycles. Differences observed in properties of starches derived from dry chips by wet and dry millings were very minimal. No indication of major change in granule structure was noted for dry-chip starch that would alter the properties relative to fresh root starch. Higher fiber content and annealing due to exposure to heat and moisture of the former accounted for most of the variations of properties as compared to the latter. With the advanced technology used in starch manufacturing industry today it would be possible to obtain starch from dry chips with similar quality from fresh root. This would enable the industry to overcome the cycle of glut and low season, and allow them to remain open for longer period of time in a year. CONCLUSION. Differences in functional properties existed between starches extracted from fresh cassava root and those from dry chip. Nearly all the pasting properties of starches from dry chips significantly differed from those of fresh roots. The starches from dry chips had lower peak viscosities, breakdowns and setbacks and higher pasting and peak temperatures. Similarly the thermal properties of dry chip starches, except a few related to gelatinization, were different from those of fresh root starches. Dry-chip starches had higher onset and peak temperatures of gelatinization than starches from fresh roots. Values of all retrogradation properties including percentage of retrogradation were also higher for dry-chip starches. However, the endotherms of the two groups of starches were almost identical except a shift by few degrees to a higher temperature for those of dry-chip starches. This suggested occurrence of no major structural changes in the granules of dry-chip starches due to chip drying and starch extraction. Moreover, dry-chip starches showed lower swelling power, paste clarity, and freeze-thaw stability than their counterpart. Percentage of syneresis increased with the number of cycles for all the three types of starches and cassava varieties. These differences in properties may have resulted largely from differences in the fiber content and also from annealing due to exposure to excess heat and moisture during processing. The differences are without severe drawback for the suitability of dry-chip starches in many applications. Furthermore, the high stability and resistance against heat and shear could be beneficial in many respects. Processing of starch from dry cassava chips resulted in more fine fiber particles in the starches and required a more efficient method of separation than processing from fresh root. It is felt that the problems indicated by earlier workers [3] in the preparation of good quality starch can easily be overcome taking into account that they had started with pellets and chips prepared for animal feed containing sand, high fiber and other impurities. It is the opinion of the present authors that with little or no modification to the modern processing equipment currently in use it may be possible to extract starch of higher purity and desirable functional characteristics from dry cassava chips which have been appropriately prepared on a commercial scale. |
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| ISSN: | ISSN 0038-9056 |
