Tapioca starch is an important raw material in processing for human foods, animal feeds, raw material for industries, and in a recent industry where tapioca starch, from tapioca chip or fresh tapioca root, is used as raw material in the production of ethanol, as an alternative fuel. The foregoing opens a new dimension in a significant utilization of tapioca. Knowledge relating tapioca root is therefore made known to interested persons and further disseminated, to be in line with the fact that Thailand is a major tapioca producer and the largest tapioca exporter in the world.

     Insofar, knowledge relating starch production producer from tapioca could be summarized as the followings.

1. Quantity of starch in tapioca root corresponds to the season

     The past researches and survey information indicates that tapioca harvested in drought seasons, particularly during the months having cold weather which are November, December, January and February, will give more starch than those harvested in other periods of time. In May and June (early rainy season) tapioca is exposed to rain and starch will be used for its tops and young leaves to grow. The tapioca root will therefore give less starch than in other seasons. The details of which are shown in Table 1.

2. Tapioca families

      In the past, tapioca cultivated commercially is in the family of Rayong 1 (Local family). In average, rainy season harvest yields an average of 16-18 percent of starch, and drought season harvest 22-23 percent of starch. Moreover, a number of farmers had been upset as the tapioca harvested for sale gives relatively low starch, and was sold at very low price. Upon introduction of new families of tapioca, namely, Rayong 5, Rayong 90, Kasetsart 50, Huaybong 60, the tapioca root cultivated by farmers normally yields 22-25 percent of starch in early rainy season, and even mare in drought season which always yields 27-30 percent of starch.

From Table 1, it is apparent that according to the survey on the quantity of starch during 1997-2002, the amount of starch in tapioca root in May and June was increased to 23-24 percent, even if it was less than 20 percent of starch acquired before that. The reason in this regard being that, since 1997, good families of tapioca have nearly replaced all of the local family of tapioca (Rayong 1).

In addition to the families mentioned above, new families being developed by Kasetsart University, with the support of the Thai Tapioca Development Institute Foundation, may give similar productivity as Huaybong 60, but yields more 2 percent of starch than Huaybong 60. In details, Huaybong 60 yield an average of 25.6 percent of starch, where new family yield an average of 27.3 percent (upon experiment of 70 test plots in the period of 7 years). It therefore ensures potential of these new families in the future, that the productivity of starch will be higher given the same area of cultivation. Hence, increasing the strength of Thai tapioca industry.

3. Soil and fertilizer

     Cultivation of the same family of tapioca in different areas, or just about the same times of cultivation and harvest accordingly will yield dissimilar amount of starch. Area where tapioca is fruitfully cultivated tends to be the same in later years due to soil nutrient, soil structure, organic substances. However, it is not to the knowledge of the academics to which nutrient exactly entrusts high starch.

The experiments conducted more than ten years indicates that there was attempt of the academics in applying fertilizer believed to increase starch in tapioca root, e.g. potassium or trace elements, but it was not found to what fertilizer exactly increase starch in tapioca root. In general, experiments found that application of either organic or chemical fertilizer will result in bigger tapioca root as well as increased productivity. However, the amount of starch in tapioca root will normally decrease in the portion of 1-2 percent as the bigger and more moist tapioca root yields decreased percentile (quantity) of starch. Nevertheless, total starch per rai, or productivity of starch per area of cultivation, increases, as productivity increases while percentile of starch obtained only slightly decreases.

The writer has followed up on a number of researches, but has found none of fertilizer formulas that could increase percentile (quantity) of starch, including the formula 13-13-21 or organic fertilizer. The writer is confident to say that what farmers and companies claim that certain fertilizers or hormones will help increase starch has not been established by any experiment.

4. Diminishing of starch in tapioca root

     Certain measures of farmers, e.g. planting tapioca by using cut off stem or several days of exposure to the air will reduce starch. Followings are examples.

4.1 Pre-harvest stem Cutting-off

     At the maturity of tapioca, farmer sometimes cut off its stem cultivating on other plots of cultivation, leaving out the portion of root and tops. The root left out on the plot will grow its tops and young leaves, becoming the other new stem of tapioca. The growth development into the new stem will consume starch contained in the tapioca root, rapidly reducing amount of starch in tapioca root in the first two months after the stem is cut off as starch is taken to grow new tops and leaves. Once the tops and leaves are abundant, the photosyn thesis will produce starch to be restored at the tops once again, as shown in Table 2. If the stem is promptly unearthed right after stem is cut off, there will be 19.06 percent of starch in tapioca root. After cutting off stem for 15, 30, 45 and 60 days, percents of starch will decrease to 14.97, 12.33, 12.21 and 12.95 percents respectively. However, should the cut off stem is left out for as long as 75 days, percent of starch will increase to 16.2 percent.

To sum up, in order to avoid reduction of starch in tapioca root, after stem is cut off, fresh tapioca root should be promptly unearthed for sale to factories. Should it is left out, it would take at least 75 days for starch to be gradually restored in the tops once again.

4.2 Post-harvest storage of tapioca root

     After tapioca is unearthed from soil, it should be promptly delivered to factories, as the unearthed root will use starch for its respiration, and the surrounding microorganism will damage such unearthed root, making it rotten. However, amount of starch in tapioca root will not be reduced in the first two days after unearthed, as detailed in Table 3. As it is unearthed, there will be 23.01 percent of starch. Similarly, in the following 2 days, the amount of starch will not reduce and stay at 23.07 percent. However, its root will start to rot at the percentile of 1.62 percent. If it is left out for 4, 6 and 8 days, the amount of starch will reduce to 20.07, 13.13 and 9.94 percent, respectively. Only within 6 days after unearthed, the amount of starch will reduce as much as 10 percent (from 23.01 percent to 13.13 percent). Within 8 days after unearthed, the amount of starch will largely reduce as much as 14.0 percent (from 23.01 to 9.94). Moreover, number of rotten roots will vary upon the length of time in storage.

To sum up, in practice, after harvest, the unearthed root should be sold to factories as soon as possible. In addition, in the future, factories should cooperate with farmers to logistically distribute the harvested tapioca and to avoiding unprocessed tapioca left at factories, as it will reduce production of starch or tapioca chip.

Table 3: Quantity of Starch and Deterioration in Tapioca Root after Unearthed

Number of Day after Unearthed	Quantity of Starch (%)	Rate of Deterioration (%)
0	23.01	0
2	23.07	1.62
4	20.07	10.80
6	13.13	23.92
8	9.94	35.21

Source: Puangpetch and groups (1979)

	References Chaya Hasdisevi, 1987, Factors in Production, Production Costs, and Profit of Tapioca Chip Factories in the northeastern region. Master Degree Thesis in Agricultural Economics, Kasetsart University. Puangpetch Narintraporn, Chan Thiraporn, and Sophon Sinthuprama, 1979, Study on the Harvest and Storage of Tapioca Root. Report on Experiment of Tapioca B.E. 2522, Department of Agriculture, pages 254-255. Sophon Sinthuprama, Chan Thiraporn, and Anuchit Thongklum, 1983, Agriculture Zoning and Plantation System for Tapioca. Academic journal volume 7, Department of Agriculture, pages 41-55. Anuchit Thongklum, Nares Sornluksup, Chan Thiraporn and Sophon Sinthuprama, 1977, Outcome of Harvesting After Stem Cut Off Toward Productivity and Quality of Tapioca. Report on Experiment of tapioca B.E. 2520, Department of Agriculture, Pages 99-102. Anuchit Thongklum, Chan Thiraporn and Sophon Sinthuprama, 1978, Outcome of Harvesting After Stem Cut Off Toward Productivity and Quality of tapioca. Report on Experiment of Tapioca B.E. 2521, Department of Agriculture, pages 142-145. Uthai Senpakdee, Kampol Narintraporn, Chan Thiraporn and Sophon Sinthuprama, 1979, Outcome of Harvesting After Stem Cut Off Toward Productivity and Quality of Tapioca. Report on experiment of Tapioca B.E. 2522, Department of Agriculture, Pages 217-222. Rojanaridpiched, C., V. Vichukit, E. Sorabol and P. Changlek. 2002. Breeding and Dissemination of New Cassava Varieties in Thailand. Paper presented at the 7th Regional Cassava Workshop, held in Bangkok, Thailand, Oct. 28 – Nov. 1, 2002.