Introduction

Molds are common contaminants of agricultural commodities. Foods and feeds. Fungal development on alimentary substrates can lead to different detrimental effects: alteration of technological properties decrease of nutritive value and synthesis of mycotoxins (Pitt and Hocking., 1985). Evaluation of molds development is of interest to estimate global quality of raw materials and may be useful to take decision on their possible use. Ergosterol is considered as the principal sterol of fungi and it plays an important role as cell membrane component Therefore, it has been proposed as a global indicator of mycological quality of foods and feeds (Bailly et al., 1999, Cahagnier, 1998, Scnurrer, 1993, Schwardorfk and Muller, 1980, Seitz et al, 1979, Seitz et al., 1977). Ergosterol levels are commonly used as quality parameters in ecological (Sashdhar et al., 1989,), industrial, (Hippelein and Rugermer, 2004), and agronomics environments (Kadakal and Artik, 2004, Sashdhar et al., 1989). Moreover, significant correlations were found between ergosterol and the major mycotoxins (fumonisin B1, Zearalenone, Deoxynivalenol, ochratoxin A, patulin) in maize (Peitri et al., 2004, rice (Saxena et al., 2001), tomato (Kadakal and Ekincir 2005) and wheat (Abramson et al., 2005). Therefore, ergosterol determination can be considered as a good index of fungal development on cereals and could be an early indicator of potential mycotoxin production. Its determination can be used in industry to screen productions, prior to mycotoxin analysis. On cereals according to Cahagnier, 1998, 3g of ergosterol per gram is considered as the maximum acceptable level for maize while for wheat, 8g of ergosterol per gram is the retained value for certifying correct quality of the grains. On the other hand, when the amounts of ergosterol are upper than 8g/g on maize and 12g/g on wheat, a doubtful quality of grains is suspected Cahagnier, 1998.

Cocoa beans, a produce of commerce of Theobroma cacao is a principal raw material for the chocolate industry. Cocoa of commercial grade should conform to some criteria among which absence from mouldiness and mycotoxin production is one (Aroyeun et al, 2007). Grading of cocoa beans into Acidity, slatiness, mou;ldiness are among the most prominent quality parameters for grading cocoa beans. All these methods are time consuming and laborious. Using ergosterol index as to measure the posssibilit6y of mycotxin production in cocoa beans has not been reported. Since the method of ergosterol determination can be a faster and relatively precise method, this study was designed with the aim of grading contaminated cocoa beans using fungal determinations, erogsterol index and ochratoxin A formation.

Materials and Methods

Raw materials

Determination of fungal counts

Extraction of ochratoxin A and quantification

Determination of ergosterol content in cocoa beans

Results And Discusssion

In table 4.38, the higher the fungal counts, the higher the ergosterol values and in most cases the higher the ochratoxin A values. This finding was in agreement with previous reports on the direct relationship between ergosterol, fungal counts and mycotoxin production (Lamper et al., 1999, Varga et al. 2002, Czaczyk et al., 2002). Reid et al., 1999 observed an interaction between Fusarium graminearun and Fusarium moniliforme and disease progress, fungal biomass and mycotoxin accumulation and ergosterol formation. Ng et al, (2008), estimated fungal growth using ergosterol assay as a rapid tool in assessing the microbiological status of grains and feeds. Ergosterol has been determined in fungal grains with different levels of fungal contamination by Maria et al., (2001). Samples CB1 with fungi counts of 62.10 x 102 cfu/g had 6.33ug/kg of ochratoxin A and 24.23mg/kg of ergosterol. High fungal counts of 33.02 x 102 cfu/g in CB4 and ergosterol content of 20.41mg/kg corresponded with the OTA observed (3.12ug/kg). .Sample CB6 with fungal counts of 30 x 102 cfu/g, had a corresponding ergpsterol content of 17.21mg/kg and a low content of OTA (1.86ug/kg). In this case, there is a possibility that OTA producing fungi might be present in the cocoa samples but maybe the OTA production capacity of the fungi was low. Samples CB1, CB6, CB8 had high fungal counts, high ergosterol and high OTA values. In sample C14, fungal counts, ergosterol and OTA did not correlate. The high OTA production, which does not correlate with either ergosterol or OTA might indicate presence of high OTA producing fungi even though it might be present in low counts. Samples CB12, and CB13 had low fungal counts; low ergosterol and low OTA in agreement with the hypothesis of Schnurrer, (1995) on the direct relationship of fungal counts, ergosterol and Deoxynivalenol. CB10 had fungi counts of 11.10 x 102 cfu/g, ergosterol of 10.47mg/kg but a correspondingly lower OTA of 0.09ug/kg indicating the presence of OTA producing fungi with low production capacity. Samples CB15, CB16 fell in the category where the ergosterol, fungal counts and OTA have a direct relationship..

The results obtained in this study supported the usefulness of the quality grading system described by Scnurrer, (1995). Based upon ergosterol and OTA content of the samples, only 18.25% of the samples reached FOQ grade (<5mg/kg ergosterol), OTA of this class is <1ug/kg and 18.25% fell in the FUQ grade with the ergosterol of 5010mg/kg and OTA >1ug/kg. 31.25% fell in the category of Screen for mycotoxin (SFM) grade having ergosterol of 10-20mg/kg and OTA in the range of 1.68-2.31ug/kg while 31.25% also fell in the last grade Fuel quality grade (FuQ) with ergosterol > 20mg/kg and OTA > . 3.12ug/kg. Based on the grading system, the cocoa beans obtained form the warehouses in the food quality grade (FOQ) included CB10, CB12, CB13. Samples in the feed quality grade (FeQ) were CB5, CB7, CB9, CB11 and CB14. Those for screen for mycotoxin (SFM) included CB2, CB3, CB6, CB15 and CB16. The fuel quality grade (FuQ) category were CB1 and CB4 respectively (table 4.39)

In conclusion, the use of ergosterol can be used as an indicator of good cocoa bean quality and to predict the possibility of ochratoxin A formation by mycotoxigenic fungi in cocoa beans. In conclusion, this index can be relevant as a rapid test for screening cocoa beans samples meant for export.

Figure 1

Table 1: Fungal contamination, Ergosterol and OTA of cocoa bean samples

Figure 2

Table 2: Cocoa Bean grading based on ergosterol value