UK-THAI maize project
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In Phase I of the project (1984) it was established that mechanical drying to 14% moisture content could effectively prevent further aflatoxin contamination. However, using driers at the local merchant and regional silo level did not produce maize with low levels of aflatoxin as incoming maize was already well in excess of 30 ppb.
During Phase II (1985), maize was collected and loaded into a drying system immediately after harvest (within 48 hours) in order to freeze aflatoxin at the lowest possible levels. The results of phase two were as follows:
1. Low aflatoxin maize was successfully produced during the rainy season in 35 trials in Loei and Lopburi provinces by mechanically drying freshly harvested maize with a history of 1 to 4 weeks pre-harvest drying in the field. The mean total aflatoxin content of maize produced during these trials was 2.5 ppb (range 0 to 16 ppb).
2. The control survey confirmed that maize at local merchants (with a history of 1 to 6 weeks temporary farm storage) and at regional merchants/ silos was already too high in aflatoxin content (in excess of 50 and 100 ppb respectively) to allow the production of low aflatoxin maize. This emphasises the need to use freshly harvested maize and mechanical driers to effectively control aflatoxin.
3. Slow drying, taking longer than two days, was shown to be inadequate in controlling aflatoxin contamination, confirming a finding in Phase I.
OBJECTIVES OF PHASE III
APPROACH TO PHASE III AND BRIEF DESCRIPTION
Phases I and II had demonstrated that dry, low aflatoxin maize COULD be produced in the rainy season. The aim of Phase III was to apply the Phase l/ll findings within the existing maize marketing chair) during the rainy season harvests of 1986/87 and 1987/88 in order to establish commercially realistic improvements to the marketing chain; produce commercial quantities of low aflatoxin maize; and monitor "project" maize from farmer to final buyer.
a) Drying and Pricing
Selected merchants and buyers with suitable grain driers were invited to participate in the project by offering to buy BAAC farmer clients' maize at a premium price. Project staff, in conjunction with BAAC, identified and contacted up-country merchants with mechanical driers. Project staff monitored the quality and costs of maize harvested, shelled and dried in various locations throughout the country.
The main points agreed with participating merchants were as follows:
In year one agreements were reached between local merchants and export silos. Direct selling links from farmer to end silo were also established.
In year two agreements were negotiated with quality conscious feedmillers on premiums and aflatoxin testing.
Farmers and merchants were interviewed to establish the difficulties in changing their current practices when trying to switch to the UTP system. This followed the work of phases I & II which showed that maize dried within a specified short time after harvest was low in aflatoxin content.
Two seminars were held with the main objectives of informing project participants and concerned parties of the project aims and implementation schedules. There was also a strong educational element aimed particularly at the BAAC credit officers.
c) The problems of drought and pre-harvest contamination
In 1987 drought conditions led to crop failures and pre-harvest incidence of aflatoxin in serveral sites. Altough maize was dried within the time limits of the semi-UTP system, aflatoxin levels at these sites were very high.
d) Evaluating the role of mould inhibitors
An alternative to fast drying of freshly harvested maize is to apply a chemical that will prevent fungal growth and hence aflatoxin. Ammonium bis-propionate (NILSPOR PLUS) solution has been shown to prevent deterioration in grain and fodder crops resulting from fungal and bacterial action.
A trial was undertaken to demonstrate that NILSPOR PLUS, when applied to fresh maize (that had been subjected to Aspergillus flavus inoculant), would prevent aflatoxin development under conditions found on Thai farms. A suitable spray applicator was also developed for use by farmers.
This work was carried out at AIT, Rangsit. Farm conditions were simulated during Aprill/May 1988 using maize that was inoculated with Aspergillus flavus spores. During 1986/87 a preliminary trial was carried out to compare two methods of chemical application. It was found that spraying was more suitable for farm application than soaking or dunking for a short time.
The economics of the early selling of maize in a falling market and the attitudes of farmers to early selling were considered. Two farmer surveys were conducted to gather information on farmer attitudes and selling practices.
f) Sampling and testing for aflatoxin
In order to monitor aflatoxin levels of both project and control maize, small laboratories were set up at one export silo and at one up-country merchant's godown. All samples were analysed by the TCO/ODNRI mycotoxin specialist at the Department of Agriculture. DOA and ODNRI were responsible for analysis of the coded samples.
SUMMARY OF ACTIVITIES AND RESULTS
Activities Year 1
Agreements were reached with two up-country maize merchants for the purchase, drying and monitoring of project maize.
Various services were agreed with the first merchant, Mr. Prapak Tarwat in Tak Fa District, Nakon Sawan Province. The supply of maize was organised by the BAAC branch office under supervision of the BAAC credit officers.
The second drier was at Wangshampoo District, Petchaboon Province. This was the sister ST3 batch type drier, on loan from the Department of Agriculture. Maize was supplied through the merchant, Mrs. Rampai Wongprayoon. Costings and performance of the machine were monitored by the project staff. A series of forms were designed in order to monitor the maize from harvesting through to final sale/aflatoxin analysis.
In Lopburi and Saraburi Provinces arrangements were made for the sale of project maize straight from shelling to the silos in the Tha Rua District, Ayuthaya Province.
All sampling and analytical work was performed at the two Tha Rua silos by the Seed and Post Pathology Branch of the Department of Agriculture, under the supervision of the Technical Cooperation Officer.
A farm survery was carried out in Petchaboon Province.
A project was carried out at the Asian Institute of Technology on the application of propionic acid at the farm level in the control of aflatoxin in stored maize cobs.
Results Year 1
The labour input required to harvest, within two days, sufficient maize to warrant shelling and transport is beyond the means of most farmers.
Often labour is not available and farmers do not have the cash to pay them. Thus the UTP criteria were not rigidly adhered to and farmers were advised, through the credit officers, to harvest as quickly as circumstances permitted.
In the 1986/87 harvest, premiums were only payable for maize less than 20 ppb. Farmers were reluctant to speed up their harvest, thus incurring additional costs, for a premium that was not flexible enough to accommodate maize above 20 ppb.
Project maize in 1986/87 was from Lopburi, Saraburi, Nakon Sawan and Petchaboon provinces. From beginning of harvest to start of shelling there was an average time lapse of 9 days.
Shelling and Drying
Shelling to delivery to drying silo was completed within 24 furs, with the exception of Petchaboon, which varied between 1.5-3 days. This reflects the difficult terrain in Petchaboon where the maize had to be brought down from the mountain by tractor and then loaded onto a pick up truck for delivery to the ST3 batch drier. Project maize going into the Tha Rua silo had a special dispensation and was allowed to go to the head of the queue and thus there was no delay before drying.
Tonnage Collected/Aflatoxin Levels
293.7% tonnes of project maize was collected from the 4 sites. 151.6 tonnes, or 51.6% of the total tonnage collected, was less than 20 ppb. The low tonnage collected reflects the unwillingness of farmers to implement a UTP or Semi-UTP system.
Chemical usage in the dipping tests was in excess of 100 litres/tonne of maize. Spraying systems were more practical and more financially viable. Laboratory determination indicated a control on fungal activity by different treatments, although in the study very low aflatoxin levels were detected, possibly due to low levels of atmosphere contamination in the research area.
The main recommendation was for further work into the design of a spraying system.
Activities Year 2
Two pre-implemention seminars were held (See Appendix 4); The first was held with the aim of informing the maize industry of the proposed project activities. The second seminar, in which all project participants attended, focussed on project implementation.
The project team worked with a total of six upcountry maize merchants. Due to a prolonged drought in the planting/growing season only four merchants operated their businesses in the harvesting/buying season. These were in Petchaboon, Chantaburi, Nan and Phrae Provinces.
Maize was supplied through BAAC branch offices. A merchant drier survey was carried out by project staff at three drier sites. Because maize loses its identity in a continuous flow drier, samples were taken and sun dried during unloading at the drier intake.
A second farmer survey was undertaken and preharvest cob samples were taken to determine the incidence of pre-harvest aflatoxin contamination. Work was done at the drier in Petchaboon on using the BGYF as a presumptive aflatoxin check.
A sub-project was undertaken involving the collection and delivery of maize to an export silo in Tha Rua. The objective was to spray the shelled maize with propionic acid to control fungel development. Samples were taken from incoming project maize and were analysed on site using a commercial aflatoxin analysis kit and by using the BGYF. Pricing difficulties between the Tha Rua silo and the final buyer meant that the maize collected was not sprayed.
The Asian Institute of Technology undertook a second year of work on the application of chemicals on cob maize. Work involved the design and construction of an on-farm, man powered, continuous flow cob sprayer. The sprayed cobs were then stored and sample were taken to check aflatoxin levels and propionic acid residues. The samples were analysed at AIT using the commercial aflatoxin analysis kit, Aflatest.
All sample generated in the projects were analysed by TLC at the Seed and Post Harvest Pathology Branch, Department of Agriculture, under the supervision of the Technical Cooperation Officer.
Results Year 2
The average harvest time for project maize was 6 days. The short time taken to harvest reflects the fact that project maize was often delivered in small quantities. The average time from the end of harvest to the beginning of shelling was 16 days. In both 1986/87 and 1987/88 it was difficult to persuade farmers either to speed up their harvest or to sell soon after completion of harvest. Pre-harvest aflatoxin contamination, positively identified at two drying sites (Petchaboon and Chantaburi), lead the project team to conduct pre-harvest sampling to identify the level of aflatoxin contamination.
Shelling and Drying
The end of shelling to delivery to drier was within 24 furs. In most cases project maize delivered to the silo was dried within 3 furs. In a few cases however, there was a time delay of up to 12 hrs before the maize was loaded into the drier. Monitoring of project maize stopped at the up-country driers because of mixing within the drier and the difficulty of judging when project maize entered and left the drier.
Tonnage Collected/Aflatoxin Levels
2098 tonnes of project maize was collected. There was no negative aflatoxin (less than 20ppb). maize. Of the total tonnage tested for aflatoxin 9.25% was between 20-50ppb. There was no negative aflatoxin (less than 20ppb). The remainder was above 50ppb. (This is explained largely by the incidence of preharvest contamination resulting from the drought).
A total of 1422.7 tonnes was collected. From the tonnage tested, 6.21% was less than 20ppb, 9.2% was between 20-50ppb and the remainder was above 50ppb.
A continuous flow rotary drum sprayer was designed and built at AIT. Control and aflatoxin innoculated maize was treated. A knapsack sprayer was used linked to the rotary drum. Work was carried out using an Ultra Low Volume spray system.
Results indicated complete cob coverage by the chemical and low chemical application rates, especially with the ULV spray system. The main recommendations were further development of the machine and implementation of farm based trials.
MAIZE PRODUCTION AND MARKETING IN THAILAND
Maize production in Thailand peaked in 1985/86. The planted and harvested area was 12.377 million rai and 11.990 million rai respectively. This is a five fold increase since 1965. Yields have fluctuated yearly due to climatic conditions and generally there has been little significant increase in yields. The increase in production reflects an increase in the cultivated area.
The 1986/87 harvest was an estimated 4.2 million tonnes with 11.982 million rai planted and 11.181 million rai harvested. World maize production was also high and this was responsible for severely depressing the Bangkok silo price. Farmers were reluctant to sell and many stored their maize through until Nov./Dec./Jan.1986/87 when they were forced to sell to repay their loans.
Low prices in 19 6/87 meant that there was less credit available for the 1987/88 season. This factor, coupled with a severe drought that killed off much of the first planting, lead to a 37% drop in harvested area and a harvest estimated at 2.31 million tonnes. Domestic demand caused a rapid price escalation that made Thai maize uncompetitive on the world market. The Grade A Bangkok daily price rose from B2166/tonne on the 1st July 1987 to B3632/tonne on 31st Jan.1988. Farmers stored their maize in order to take advantage of a rising market.
Maize is typically a low input-low output system. It would appear that most farmers would prefer to sell their maize as soon as possible after harvest. Few farmers however, are able to sell soon after harvest. There are the physical problems of access, transport, availability of sheller etc. There are also problems of rising and falling markets, weight penalties for wet maize and credit terms that might delay the farmer's sale.
Since the loss of the Japanese and Taiwanese markets there has been considerable expansion in the Southeast Asian (Korea, Singapore, Malaysia) and Middle Eastern markets (Saudi Arabia, Kuwait, Iraq, Iran).
There is also a regional variation in the timing of the maize harvest, the likely moisture content at harvest, deliveries onto the market and need to store, particularly because of inaccessibility during the wet season.
There are maize growing areas which concentrate on early planting, harvest and early sale. This maize is harvested and sold around June/July because prices usually start falling as the bulk of the maize crop is harvested. This maize is usually of high quality/low aflatoxin and feed millers are willing to pay above the market price to secure this maize.
There are two official grades of Thai maize-1 and 2. Although aflatoxin levels are not contained in either US or Thai maize standards, importers are increasingly specifying aflatoxin levels. In certain cases aflatoxing levets at loading are above those specified in the contract although pre loading levels might be within the aflatoxin specification.
The overseas markets for Thai maize, in Southeast Asia and the Middle East, are strategically placed for small shipments in bags. Traditionally these markets have been less quality conscious but there is a danger of Thailand losing a share of these markets if higher quality maize, particularly low aflatoxin maize, could be economically sourced from other maize producing countries.
The markets for quality maize in Thailand are with the feed millers, many of which are vertically integrated. They consistently pay higher prices than export silos for maize of the same quality.
Approximately 31% of Thai maize was used domestically for feed up to 1985. In 1986187 and 1987/88 the figures were 37% and 86% respectively. The tonnage used domestically rose between 198611988. The jump in 1987/88 can be attributed to three main factors. 1) The small 1987/88 harvest. 2) The increase in livestock numbers. 3) The high price of paddy rice.
Observations on the 1985 harvest suggest that, theoretically, it is worth spending up to $10 per tonne to ensure maize is below 20ppb and $5 per tonne to meet grade A specification - $15 per tonne in all. This statement is still true if the price differential between Thai and US maize is $15 or more per tonne. However the extent to which sellers may be able to achieve a high price for quality depends upon market conditions. Price differentials between Thai and US maize in 1987/88 season showed Thai maize at an average of $26.48/tonne above US maize.
Given the current Thai maize situation, a system of pledging maize at an upcountry drier with a premium for quality might offer a realistic way out. Here an early release from the farm and timely drying could result in quality maize and a realistic price to the farmer. The limitations of the weight correction for moisture content in Thailand, with its lack of incentive for merchants to dry to 14% moisture content, was noted in Phase I and 11 reports. An alteration to the weight correction scale is recommended to increase the attractiveness of drying as near to the areas of production as possible.
MECHANICAL ASPECTS OF DRYING AND SUNDRYING
It was noted in both Phases I and II that the delays in moving the maize from the farm to the existing buying centres is largely responsible for the development of high levels of aflatoxin in the grain.
At the farm level little attempt is made to dry the harvested cobs. Although field drying is a widely accepted practice, there is a serious constraint on field drying in areas where double cropping is practised. Mung bean and soya bean are frequently planted after maize and farmers will not field-dry their maize because of the need to plant the next crop while there is sufficient moisture in the soil, and a possibility of late rain.
A few farmers will attempt to sundry a portion of the harvested cobs prior to crib storage. The cobs are often spread on a sheet of plastic, galvanised sheet or tarpaulin. The farmer must constantly be in the vicinity, however, to collect up the cobs before impending rain. For this reason many farmers are reluctant to attempt on-farm sun-drying.
Sun-drying is still the most widely accepted upcountry method for reducing moisture content. Merchants make every effort to obtain the maximum moisture reduction, usually to the detriment of maize quality. When the merchant makes a decision, based on weather conditions, to sun-dry his maize he is then committed to pay the sun-drying costs. If it starts raining and the merchant cannot achieve a moisture reduction to cover his sun-drying costs, then he has the choice of selling the maize, perhaps incurring a loss on the sun drying costs, or he can hold the wet maize and wait for weather conditions to improve to continue sundrying. If the merchant chooses the latter course then the maize quality will suffer adversely.
Whilst some merchants appreciate the improvement in maize quality through mechanical-rather than sun-drying means, most merchants are interested in the margin over drying costs. Quality premiums are generally not big enough at present to warrant investment in mechanical driers to produce quality.
Maize that can be sun-dried, under sunny conditions in one day, is often of high quality but the sun-drying floor must be clean and tractor use must be limited to avoid cracking the kernels.
Mechanically dried maize can also be of high quality provided that the maize is dried at the correct temperature and is free from smell and uncombusted burner fuel. A pre-cleaner should also be incroporated to reduce dust and chaff.
The continuous flow driers monitored in the project make it difficult to keep maize of differing quality apart, due to the mixing of the maize within the drier This can make it difficult for merchants to offer a premium for specific loads.
Merchants with driers, in general, appear not to link their purchasing to the drier's capacity. Some merchants use their drier in combination with their sundrying floor, while others do not use their sun-drying capability at all.
There is little opportunity to mechanically dry other crops and spread overheads. Mung bean and soya bean, crops which are commonly grown after maize, are harvested in the dry season. Rain-fed rice is harvested in the dry season. In areas where water is available, and rice is double cropped through irrigation, there is little maize grown. There are also very few upcountry merchants who trade in both rice and maize. Most rice traders, often with a rice mill, trade only in the one commodity.
SUMMARY OF ANALYTICAL STUDIES AND SAMPLING PROCEDURES
In the first year all quality assessment was carried out in exporters' silos in Tha Rua, Ayuthaya Province. Sampling was carried out on incoming trucks as detailed in section 7.2.1 In the second year similar sampling procedures were taken at the up-country silos which participated in the project.
In year 1 BGYF tests were compared with minicolumn analysis at the exporters' silos. In year 2 BGYF tests were carried out on all incoming maize at the Petchaboon silo. At the export silo in Tha Rua, Aflatest and BGYF analyses were undertaken. Aflatest was also performed on the experimental batches at AIT. All these results were confirmed by HPTLC analysis at the Department of Agriculture.
It is estimated that some 40% of maize-producing areas are inaccessible during the rainy season. This is particularly the case in the newly developed areas that have been claimed from the mountainous forest reserves. In these areas it is not practical to bring freshly harvested maize down to the villages and main roads until the dry season enables traffic access.
To avoid fungal attack of cobs that are harvested during this period would require either that a drier is located very close to the fields or that some alternative form of treatment is considered. Whilst mechanical drying is possible in certain areas, another possibility is the use of chemicals such as ammonium his propionate solution to repress the growth of fungi.
Work has already been carried out to assess the effect of chemical control on shelled maize prior to loading on to export vessels during the rainy season. Little has been done, however, to research the effectiveness of chemical control on maize cobs immediately after harvesting. Development of application techniques and application rates would be necessary to develop a suitable system that would would be effective at farm level. Any applicator so developed would need to be cheap and simple to use.
To develop this work, AIT were approached to set up a programme to compare dunking of cobs in the chemical solution with spraying, using a purpose built sprayer suitable for farmers' use. The rationale behind this approach follows from the work done in Phases I & II of this project. This showed that normally maize is low in aflatoxin level immediately after harvest but that the level builds up rapidly in farm storage during the wet harvesting months of August and September. If treatment with chemical at this time, immediately after the harvest, it is successful in controlling fungal growth the resulting maize should be low in aflatoxin content. The detailed objectives, methodology, findings, conclusions and recommendations are to be found in Appendix 1. After the first year's study it was decided that further work was necessary to refine the application of spray chemical. The second year's work is presented in Appendix 2.
Summary of Conclusions from the Project
Over the four year period of the project a great deal has been learnt and is recorded in the reports on the three phases. Before making the final recommendations from the project it well be helpful to summarise the conclusions of the project in relation to its overall aim of finding an economic solution to the problem of aflatoxin in maize in Thailand.
From Phase I it was concluded that:
From Phase II it was conclude that:
- field drying maize for 1-4 weeks before harvesting to reduce moisture content to less than 22% mc. (Field drying is an important component of the UTP system because it reduces the cost of mechanical drying, helps to stagger the harvest and can probably improve shelling efficiency). Field trials conducted by the UK TCO project confirmed that drying to a moisture content of 22% could be achieved within 2 weeks during the rainy season. There was no increase in aflatoxin or decrease in physical quality over a 6 week period of field drying. However field drying should not be practised when drought has predisposed the crop- to pre-harvest contamination.
- shelling within 24 hours, certainly 48 hours, and loading the shelled maize into the drier within a further 12 hours.
- completing the drying process to a moisture content of 14%, with no part exceeding 15%, within 48 hours.
From Phase III it is further concluded that:
A summary of recommendations is given below. These have been widely discussed and agreed with the various sectors of the Thai maize industry.
1. Harvest and Post Harvest Practice
Farmers should be encouraged to allow standing crops of maize after crop maturity to dry out for one or two weeks before harvesting.
Encouragement should in the first instance be undertaken by the relevant Government Agencies i.e. DOAE and BAAG Once the benefits of field drying are widely accepted, maize merchants with good silo facilities should be advised by DOAE that the pursuit of such practices by farmers will lead to better quality (and hence higher prices)
2. Merchants should be encouraged by agencies such as DOAE and BAAC to dry maize rapidly after harvest; specifically to shell maize within 5 days of harvest; start grain drying immediately or within 12 hours of shelling; and use drying systems capable of drying maize to 14% mc (no part exceeding 15% mc) within a 48 hour period.
3. Drying to 14% MC
The specification for moisture content for Grade 1 export maize should be reduced to an average moisture not exceeding 14% by weight, but the MC of any portion must not exceed 15% by weight.
As the Office of Commodity Standards (part of the Commerce Ministry) are responsible for the official export standards, it is the Minister of Commerce who should authorise a review of possible changes for export maize.
4. Aflatoxin quality control should be used by all merchants with drying facilites to identify truck loads of maize which are whithin a 50 ppb limit and these loads should be kept separate and dried as in 2) above.
Encouragement should be undertaken by Government Agencies such as DOAE and BAAC as well the TMPTA and Feed Millers Association.
5. Incentives for Quick Release of Maize After Harvesting
Pledging and contract schemes should be developed to encourage farmers to release their harvested crops immediately after harvest.
BAAC has had experience of pledging schemes such as the large scale scheme for paddy rice in 1987/8. BAAC is recommended to carry out a pilot scheme with one or two approved merchants. Obviously such a scheme will only be brought into action if market conditions are such that farmers are anticipating rise in price.
In addition, Feed Millers who have identified supplying merchants following acceptable quality control procedures should experiment with forward contracts for quality maize. A feature of such contracts should be that farmers benefit through early release of maize. This might be achieved by a premium price linked to an input supply scheme (often referred to as a total package scheme).
6. TMPTA Weight Scale
To provide incentive for farmers and traders to dry maize mechanically, the TMPTA weight scale should be altered to provide an incentive of at least 20 kgs per tonne per one per cent of moisture removed down to 14% moisture. Such a scale should replace the existing scale which does not give any incentive to dry below 18% mc.
As the name implies, the scale was initiated by the maize exporters at a time when Thailand's maize industry was developing. It is suggested that the Feed Millers Association should agree with TMPTA before approaching the Minister of Commerce.
7. Recognition of Silo Operators
Merchants operating in the maize producing areas, who are prepared to dry mechanically maize that has been freshly harvested and will offer a premium to the farmers, should be encouraged, recognised and approved.
Encouragement can be given by quality conscious buyers such as feed millers. Government organisations such as BAAC and DOAE should establish a scheme of approval and promote those individual merchants who follow there practices.
8. BOI Privileges
In order to encourage merchants to pursue the production of quality maize through mechanical drying and to encourage local farmers' participation, BOI should give consideration to awarding privileges to such merchants who make application.
Feed Millers will stand to gain most from the development of such improved up-country merchants and will be the most likely group to succeed in persuading the 801.
9. Training of Merchants
Training should be offered to merchants in the following aspects of their business in order to improve quality:
Choice of suitable plant and equipment
Cost control and financial planning
Communication skills with farmers
This training should be offered by the TMPTA and Feed Miller's Association, in cooperation with DOAE and DOA.
10. Laboratories in Maize Growing Areas
Encouragement should be given to the establishment of laboratories to pursue better methods of quality control in the maize producing areas. The function of such laboratories should include:
a.) Standardising and assessing moisture content of maize (and other crops)
b.) Monitoring and reporting the quality of local crops pre and post harvest. This will include assessment of aflatoxin content in the area.
c.) Supplying mini-column kits, including the regular supply of mini-columns, to merchants.
d.) Carrying out aflatoxin analysis of samples submitted by local traders and farmers.
e.) Recommending and teaching the adoption of good quality control techniques.
f.) Publicising and utilising agreed national methods of sampling.
g.) Testing and publicising other new quality control techniques as they become available.
Establishment of a laboratory in Tha Rua may be economically feasible for an existing inspection company. In the maize growing areas the Department of Agriculture should be encouraged to investigate the setting up of laboratories in their field crop-stations such as Petchaboon and Tak Fa, Nakon Sawan.
11. Inspection of Export Consignments
The Government should establish standard methods for sampling consignments of maize of different size in bags and in bulk. The standard method should apply equally to export shipments and domestic trade.
The Office of Commodity Standards should propose suitable sampling methods for consultation by the inspection companies and exporters. After consultation agreed methods should become standard practice and widely known. (see 7.9.4)
12. Sampling for Quality Control
Sampling and sample handling procedures should be modified to reduce the risk of batches passing PreLoading and Loading inspection, when they actually exceed the specified aflatoxin limit. As a first action Inspection Companies should install mills at each of the silos at which they are working. A minimum bulk sample size of 5 kg should be taken for aflatoxin quality control testing. The sample should be collected from throughout the batch, and should be coarse-ground before division to 2 kg and then fine-ground to pass a 1 mm screen before further division. For BGYF testing a 2.5 kg sample of kernels will usually be adequate. In The longer term, sampling plans designed to further reduce Consumer (Buyer) risk, such as that currently being devised by the Thai-UK Post Harvest Technology, (Aflatoxin in Maize) project, should be considered.
13. Cost of Mechanical Drying
Research should be carried out into the economics and efficiency of using biomass as an energy source for mechanical drying. Further development of biomass burners and gasifiers is needed, especially for small batch driers that would be suitable for primary merchants.
The responsibility for such research lies with the Division of Agricultural Engineering (DOA) in cooperation with the Trade Associations.
14. Farm Storage
The evidence gathered by the Thai-British project clearly indicates that temporary farm storage of undried maize cobs leads to a build up of aflatoxin contamination. Because farm storage is so widely practised and will be hard to change, it is recommended that further research work is undertaken on field drying and temporary farm storage.
15. Training & Education of Farmers
More extension work is needed to educate farmers in the principles of post harvest management and marketing. Farmers should be taught about the effect of moisture content on the price. Market information should be explained so that they can learn how to compare broadcast prices in baht per picul with their own local prices.
In particular, this training should include:
The effect of moisture content on deterioration and toxin formation
The effect of moisture content on the sale price
The benefits of field drying
The relevant broadcasting authority should be made aware of these problems.
16. Asian Institute of Technology
Year two results from the Asian Institute of Technology indicate that the continuous flow cob sprayer, with minor modifications, could be used at the farm level. Further work should be undertaken with the aim of producing a practical and economically viable prototype for commercial production.
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