Ergosterol content in commercial tomato products as an index of raw-material microbial contamination and search for a correlation with the Howard mold count

Inglés. Ergosterol, a constituent of the cell wall of some important vegetable parasites such as molds, has been recently recognised as a potential objective parameter useful for the characteristics of the quality of processed tomatoes. The present work tries to ascertain whether there are any correlations between HMC (the Howard Mold Count, which has been used for many decades and which has been repeatedly criticised for its subjectivity) and ergosterol level or, at least, whether it is possible to find a correlation between ergosterol level and incidence of mold contamination of the raw material. The work is based on: improvement of a HPLC method for ergosterol determination; preparation of tomato concentrates from raw material with different percentages of rotten fruits; HMC and ergosterol determination in the concentrates obtained; and search for correlations between HMC and ergosterol content. The analytical method proved reliable, with a detection limit of 0.1 ppm. No relation was found between ergosterol level and HMC. However, rotten-fruit percentage turned out to be related both to ergosterol level and to HMC value, in the former case more closely than in the latter. Of course, considering the high cost for HPLC apparatus and the long analysis times, the determination of ergosterol can be of interest only for quality evaluation of finished products, while its adoption for factory routine controls seems very problematic

Italiano. Recentemente e' stato individuato nell'ergosterolo (costituente della parete cellulare di alcuni importanti parassiti vegetali quali le muffe) un possibile parametro oggettivo per caratterizzare la qualita' del pomodoro utilizzato per la produzione dei derivati industriali; la presente ricerca ha cercato di valutare se esiste una correlazione fra HMC (Howard Mold Count, metodo utilizzato da decenni e ripetutamente criticato per la soggettivita') e contenuto di ergosterolo o almeno se sia possibile individuare una correlazione fra ergosterolo trovato e grado di contaminazione fungina della materia prima. Lo studio e' consistito nella messa a punto di un metodo di determinazione dell'ergosterolo mediante HPLC; nella preparazione di campioni a partire da percentuali diverse di frutti contaminati con relativo studio della qualita' dei derivati (HMC e ergosterolo) e nello studio di eventuali correlazioni fra i due parametri