Prevention of Mould Formation in Coffee

1. Introduction
In recent years, reports on the occurrence of Ochratoxin -A (OTA) contamination in coffee are causing great concern in the trade. OT-A is a mycotoxin (toxin from moulds) produced by moulds like Aspegillus and Penicillium and has been shown to be toxic to kidneys in many test animals. Cereals and their products are the main dietary source of OT-A. Coffee seeds are also liable to mould contamination especially, if they are not dried to properly or if re-hydrated during any stage of drying, storage and transportation. Studies carried out in Europe indicated that occurrence of OT-A in various commercial samples of raw roast and instant coffee originated from different countries.

Realizing the health risks associated with the intake of OT-A through various dietary sources including coffee, the coffee importing especially, the European Union (EU) has prescribed maximum OT-A levels of 5ppb for roasted coffee beans and ground roasted coffee and 10 ppb for soluble (Instant) coffee and no limits for green coffee as of now. However, the Commission has proposed to review its position regarding the limit on green coffee beans by mid - June 2006, based on the up-to date OT-A risk assessment data.

It any such limit were established for green coffee, it would adversely affect the global coffee trade. Further, as there is no alternative use for green coffee other than consumption as beverage refection by importing countries will cau'se loss of export value for the producing countries and such as rejected lot may be consumed within the country. It is therefore, a matter of great concern that the coffee industry in the country be aware of the latest position on OT-A in coffee and the steps that are required to be taken to minimize the OT-A contamination in Indian coffees. In this article, a detailed over view on the latest position is presented for the benefit of the all sectors of the industry.

A. Genesis of tlte OT-A Problem

Though the presence of OT-A in green coffee was first reported in 1974 (levi, et.al.), the occurrence of OT-A in coffee has attracted worldwide attention ever since the Hungarian Health Authorities first rejected a coffee consignment during 1994 citing excess levels of OT-A (The Public Ledger News, 1995). Determination of OT-A levels in export and commercial coffees have been extensively carried out since the first report of OT-A contamination in coffee by Levi, et.al. (1974). Several authors have demonstrated the natural occurrence of OT-A in green coffee and finished coffee from various origins and these results indicated that OTA contamination may be more frequent in some areas but no producing country is entirely free from OT-A contamination. The presence of OT-A in the coffee beverage was reported only in 1995 by Studer-Rohr, et.al.

B. Moulds responsible for OT-A production in coffee

As discussed earlier, OT-A is a mycotoxin produced by moulds like Aspegillus and Penicillium. It is predominately produced by two fungal species, Aspergillus ochraecus and Penicillium verrucosum. Aspergillus ochraecus is more prevalent in tropical conditions and it is the important OT-A mould producing species in coffee.

OT-A is found in many foodstuffs, mainly in cereals and on grapes but also in coffee beans. These moulds will only grow on foodstuffs that have been subjected to high levels of moisture. In coffee, this leads to development of mouldy green coffee having unacceptable flavor and also OT-A contamination. It is 'well documented that in coffee, OT-A producing mould viz. A.ochraceus formation can occur when the water activity (free water content) level is above 0.8 (=d6% moisture content) and its growth is accelerated when aW level reaches 0.9 (~27%moisture content). Similarly, it has been demonstrated that in coffee, initial OT-A mould contamination may occur at farm level, the actual OTA formation may occur throughout the entire chain in every stages viz, processing, storage and transportation.

C. Significance of OT-A contamiration in coffee

Studies carried out in the European Union (EU) have revealed that Cereals and their products account for major source of dietary intake of OT-A (56%) followed by wine (22%). Coffee is reported to be third major contributor of OT-A to the total dietary intake with 4-7% contribution of OT-A. Thus coffee has also become an important food commodity in terms of OT-A related safety concerns in the EU. However, the risks associated with OT-A cannot be san1e in other countries where the dietary habits are totally different from those in Europe.

D. The effect of OT-A on human healtlt

OT-A has been shown to be nephrotoxic causing kidney tumor in mice and rats (WHO Report, 1996) and has been classified by the International Agency for Research on cancer into the "group 2B as possibly carcinogenic to humans" (IARC Report, 1993). It is also reported to be genotoxic but it is still unclear.

E. The Tnternational regulatory situation on OT-A in coffee

As on date, the Codex Alimentarius Commission (CAC) which is an inter - governmental body established jointly by the governing bodies of FAO and WHO in 1962, to elaborate standards on food quality and safety, has not prescribed any maximum limits for OT-A in Coffee Products. Further, the European Union (EU), as per it's recent Regulation (EC) No. 123/2005 of 26th January 2005 has prescribed maximum OT-A levels of 5ppb for roasted coffee beans and ground roasted coffee and 10ppb for soluble (Instant) coffee and no limits for green coffee as of now. The Commission had proposed to review its position regarding' the limit on green coffpe beans by 30th June 2006, based on the up-to dateOT-A risk assessment data. The coffee producing countries had issued a declaration, during the September 2005 meeting of the Executive Board ofthe ICO, urging the EU to reject the adoption of maximum OTA levels for green . coffee.

A recent study had cast doubts on .any lihk between OTA and carcinogenic properties in the quantities indicated and the matter is still being carefully studied by the EU. The European Foods Standards Agency had not yet published its opinion but was understood to have concluded that there was probably no foundation for classification of OTA as genotoxic.

Such a classification would have required more stringent controls. In view of this, the issue is being examined by SANCO Working Group which would review green coffee and other coffee products together with other food stuffs in the light of latest inforn1ation. Although the EU has not prescribed any OT-A limits for green coffee, few individual member countries viz, Czech Republic, Finland, Germany, Greece, Hungary, Italy, The Netherlands, Portugal, Spain, Switzerland arid Japan have adopted national level ma'l.imum limits and the details on the same is given in table.I.

Table 1. Maximum Permissible Limits imposed for Ochratoxin - A (OT-A) in Coffee Products by various importing countries.
Countries	Limits Fixed for OT-A in Coffee Products in (ppb)
	Green Coffee	Roasted Coffee	Instant Coffee
Czech Republic	10	10	10
Finland	05	05	05
Germany	*	03	06
Greece	20	*	*
Hungary	15	10	10
Italy	08	04	04
The Netherlands	*	10	10
Portugal	08	04	04
Spain	08	04	04
Switzerland	05	05	05
Japan	05	*	*
* - No Limits Fixed

The limits prescribed by EU for roasted and soluble coffees have been accepted by most of the producing countries, as they will not immediately affect their green coffee exports. However, the national limits announced by individual countries are becoming barriers for trade. Further, the coffee producing countries have suggested that EU may persuade its member countries to lift the OT-A limits on green coffee as they are appear to be based on general national rules on food safety rather than on any sound scientific analysis.

F. Code of Practices for tlte Prevention of A10uld Formation

Research studies carried out for the past one decade have indicated that the problem of OT-A contamination in coffee could be effectively controlled by preventing the incidence of moulds during processing and storage. The International Coffee Organization (lCO); the Food and Agricultural Organization (FAO) of the United Nations; the/European Coffee Cooperation and the OT-A Task Force have been constantly engaged in educating the coffee producers and processors around the world about the Good Agriculture Practices (GAPs) and Good Manufacturing Practices (GMPs) preventing mould formation in coffee. Based on the results obtained under the international collaborative project, the ICO has issued a circular which describe the GAPs/GMPs for mould prevention in coffee the circular is reproduced below for the benefit of all those connected with coffee industry.

GAPs and GMPs for Prevention of Mould Formation in Coffee:

During Harvest: a) the soil under tree should be covered with a clean sheet of plastic during picking to avoid cherries getting contaminated by dirt or mixed with up with mouldy cherries (gleanings) from previous harvest, b) cherries that have fallen to the ground are taken to be susceptible to mould growth and therefore shouldnot be picked, c) process fresh cherries as quickly as possible. Avoid storage of cherries, especially ripe and over ripe ones, as any period of storage (in a bag or in a pile) increase the likelihood of mould growth, d) do not dry on bare soil: use trays or tarpaulins. Mould spores from previous lots are known to remain on the ground and this could result on clean cherries being contaminated during drying, e) the layer of drying cherries should not be more than 4cm thick after the first 2-3 days of drying, f) drying cherries must be regularly raked (5-10 times per day), g) protect cherries during drying from rain and night dew, h) avoid all rewetting of partially dried and dried cherries, protecting them from moisture and rain.

During Primary Processing: a) Site processing plant in a dry area not in a swamp, b) only accepts for processing cherries at a uniform moisture content as low as feasible but certainly not higher than 12.5%, c) dispose of pulp from wet processing away from clean dry coffee and compost it before using it as mulch in filed, d) keep equipment facilities clean, separating residual partially processed material and accumulation of dust and discarded material, e) clean coffee from all husk material-more than 90% of mould comes from husks in sun dried cherries, f) remove any defects (husks, unhulled cherries or mouldy beans as possible), g) use clean bags for storing and transporting cleaned dried beans, h) keep separate cleaned dried beans from discarded materials, i) prevent recontamination by avoiding contact of clean green beans with dust, husks and dirty bags, j) do not store cleaned dry green coffee near rejects and husks.

During Transport and Storage: a) cover bags during transport and storage to prevent re-wetting, b) load and unload trucks or containers only in dry weather or under cover, c) do not use damaged containers and prevent water leaks, d) make sure that pallets or wooden floors of trucks and container are dry, e) store coffee in a well ventilated and leak proof ware houses. Store away from the walls, t) cover bags/ loose beans in container with water proof or water absorbent cover to prevent re-wetting of the top layer of coffee from condensation and g) provide good quality control tests and ensure that they are adhered to especially to check for moisture and defects.

Recently, the European Coffee Federation Bureau has recently approved a document entitled "OTA Management-Guidelines for Buying Green Coffee". These guidelines are in addition to the separate "Code of Practices for the Prevention of Mould Formation" which provides recommendations to all the participants in the chain on how to prevent mould formation and OT-A contamination. The key messages delivered in this guideline are depicted in the form of a decision tree diagram.

As could be seen from the decision tree diagram that the green coffee looks clean, smells clean, there is hardly any ri,sk of serious OT-A contamination. Coffees without any earthy / mouldy smell showed less than 1% OT-A risk. If any coffee lot found to contain more amount of OT-A risk defects such as cherries, skins, husks and insect damage should be subjected for OT-A analysis and it is advisable not to use such a coffee lot if it contains OT-A level more than 15ppb (parts per billion).

G) Effect of roasting and Decaffeination on OT-A:

Several studies have been conducted to study the effect of roasting on OT-A and these results have clearly shown substantial reduction of OTA ranging from 69% to 96%. Further, studies have also shown that the process of decaffeination removes about three quarter of OT-A present before decaffeination, as OT-A is quite soluble in the extraction medium normally used for decaffeination. Taking a conservative reduction of 2/3rd of OT-A during roasting process, a green coffee lot could have a maximum of 15ppb OT-A contamination which would result in finished products (be it be roasted or soluble) having a OT-A level that does not exceed European maximum limits.

Conclusion

There is widespread agreement that the focus of any effort to reduce OT-A contamination of coffee must be the application of Good Agriculture Practices (GAPs) and Good Manufacturing Practices (GMPs) and Good Hygiene Practices (GHP) throughout the coffee chain to avoid the formation of OT-A. These recommended practices are non-costing and easily adoptable. By preventing the mould growth, we cannot only eliminate the OT-A contamination, but also increase the overall quality and acceptability of coffee in the market. The prevention is the best approach is respected world wide in case of food contaminants like OT-A as it is much cheaper when compared to the cost of testing and compliance.

References

1) Levi, et.al. (1974). The occurrence of Ochratoxin-A in green coffee beansJ. Assoc. Off. Anal. Chern. Vol. 57, 866-870.
2) Studer-Rohr, 1. et.al (1995). Ochratoxin-A in green and roasted coffee beans. ASIC 15e Colloque, Montpellier. 443-452.
3) ICO document on "OT-A Risk Management Guidelines for Green Coffee Buying" dated 11th January 2005.
4) ICO document on "Update 3 on OT-A" dated March 2002