Factors influencing fungal and aflatoxin levels in Turkish hazelnuts (Corylus avellanaL.) during growth, harvest, drying and storage: A 3-year study

Abstract

The levels aflatoxins in Turkish hazelnuts have been monitored over a 3-years period (2002)(2003)(2004). Periodical sampling was made in 72 different orchards at different locations representative of the hazelnut-growing areas and post-harvest applications. Various parameters (aflatoxins, water activity, moulds) were analysed and environmental conditions (temperature and relative humidity) recorded during growing and at different stages of harvest and post-harvest processing, involving three different harvesting methods (collection in nets, from the ground, etc.) and four drying techniques (traditional sun-drying, mechanical drying, etc.). Fungal and aflatoxin analyses (HPLC) showed no significant difference except between samples which had been in contact with the ground and those which had not (at 95% confidence level). Aflatoxins levels from the orchard recorded a maximum of 0.77 AE 0.08 ng g À1 from a total of 1624 samples. Regarding harvesting and post-harvest processes, the only application where aflatoxins were detected was in samples which had been in direct contact with the ground (max. 3.18 AE 0.03 ng g À1 ). Aflatoxin formation was low during storage (max. 0.34 AE 0.003 ng g À1 ). As a result of mycological studies, a total of 5546 Aspergillus flavus (89%) and A. parasiticus (11%) species were isolated and identified from samples. The results indicated that harvesting hazelnuts into a canvas by shaking the trees, manual harvesting of mature hazelnuts where possible, use of jute instead of nylon sacks and mechanical drying technique would minimize aflatoxin levels in hazelnuts. These recommendations have been implemented and about 4000 people in the hazelnut industry have been trained in these practices.

Effect of Drying Methods on Some Chemical Characteristics of Hazelnuts (Corylus avellana L.) During Storage

“…In another study, however, a w was reported to increase at the end of the 24. months storage period (0.50-0.54) (Demirci Ercoskun, 2009). It has been reported that AF may develop if the a w exceeds 0.83 for two days (Ozay et al, 2008). The a w in our study has never exceeded 0.72 in any drying methods and storage time.…”

“…The GG and CG which are a traditional drying methods, increases the mold growth and mycotoxin risk because they are not hygienic, the drying time changes depending on the climatic conditions and the product is rehydrated. For this reason, DM of hazelnut instead of drying in the sun is suggested as an effective method to prevent AF (Ozay et al, 2008) because, in natural drying conditions, the humidity value can rise very much. Despite the fact that in our work the specimens have been preserved under the common storage conditions which is suitable for the development of fungi, no AFB 1 and total AF have ever been detected in any drying methods and storage time.…”

Determination of aflatoxins in walnut sujuk and Turkish delight by HPLC-FLD method

“…In Turkish hazelnuts, the mould count ranged between 1.8 Â 10 1 and 3.8 Â 10 6 CFU g À1 from flowering stages to harvest. A. flavus (89%) was found to be more common than A. parasiticus (11%) on hazelnuts cultivated in Turkey over a 3-years period (2002e2004) (Ozay et al, 2008). In similar, the high incidence of B-group AFs contamination rather than G-group in both walnuts and hazelnuts obtained present results might be due to both occurrence and invasion of nuts by A. flavus rather than A. parasiticus.…”

Prevalence and potential for aflatoxin contamination in groundnuts and peanut butter from farmers and traders in Nairobi and Nyanza provinces of Kenya

“…Groundnuts exported from Sudan to EU have previously been rejected owing to failure to meet aflatoxin standards (Hanafi, 1987). Thus, the purpose of reducing aflatoxin contamination levels in groundnuts should be to minimize food safety concerns and also for economic reasons (Ozay et al, 2008). A high proportion (80%) of raw groundnut samples from the cottage industry had aflatoxin levels below 10 µg/kg.…”