Control of mould contamination on industrial hemp seeds by gamma irradiation

Ozračivanje prehrambenih proizvoda je fizikalna metoda obrade hrane s ciljem uklanjanja mikroorganizama, a najčešće se koristi gama zračenje kobalta- 60. Cijena ozračivanja i nepovjerenje potrošača su razlog zašto ozračivanje hrane nije toliko rašireno u usporedbi s klasičnim metodama dobivanja zdravstveno ispravne hrane. Smatra se da je doza od 10 kGy gornja granica za sigurno i učinkovito ozračivanje hrane. Uzgoj industrijske konoplje, Cannabis sativa L. subsp. sativa, postaje sve popularnije. Sjemenke industijske konoplje se koriste u prehrambene svrhe i moraju biti zdravstveno ispravne. Cilj ovog rada je bio identificirati plijesni i odrediti njihov broj na dva uzorka kontaminiranih sjemenki industrijske konoplje. U drugom dijelu istraživanja kontaminirane sjemenke su ozračene dozama od 1,3,5,7 i 10 kGy. Uspoređivan je broj identificiranih plijesni prije i nakon ozračivanja. Uzorci se pripreme na način da se serijski razrijede u peptonskoj vodi i potom nasade na hranjive podloge Dikloran rose bengal kloramfenikol agar (DRBC) i Dikloran 18% glicerolni agar (DG18). Ploče se inkubiraju na 25ºC, a između 5. i 7. dana inkubacije izbroje se porasle kolonije. Rezultat se izrazi kao broj plijesni po gramu proizvoda (CFU/g). Identifikacija plijesni se provodi po primarnom ključu prema Pitt i Hocking, 2009. Kontaminirani uzorci se ozrače dozama od 1, 3, 5, 7 i 10 kGy brzinom zračenja od 120 Gy/min. Ozračivanje je provedeno gama zrakama kobalta-60 u Laboratoriju za radijacijsku kemiju i dozimetriju Instituta Ruđer Bošković. Po prethodno opisanom postupku ozračeni uzorci se nasade na DRBC i DG18. 7., 14. i 28. dana broje se porasle kolonije. Ukupan broj plijesni na kontaminiranim uzorcima je 7,8 x 105 CFU/g (DRBC) i 2,5 x 105 CFU/g (DG18). Identificirane su Fusarium spp., Cladosporium spp. i Alternaria spp. kao prirodni kontaminanti sjemenki industrijske konoplje. Fusarium spp. i Cladosporium spp. su dominantne vrste čiji je udio 60%. Sve korištene doze zračenja su smanjile prirodnu kontaminaciju plijesnima za više od 90%. Broj plijesni koje su preţivjele zračenje je između 1500 i 5900 CFU/g, što je približno 0,20 i 0,76% početnog broja plijesni. Nasađivanjem ozračenih uzoraka na hranjive podloge identificirane su Fusarium spp., Cladosporium spp., Aspergillus fumigatus i Phoma spp. Doze gama zračenja do 10 kGy značajno smanjuju broj plijesni u kontaminiranim uzorcima. Za potpunu eliminaciju plijesni potrebno je uzorke ozračiti dozama iznad 10 kGy.Food irradiation is a physical method of food processing to eliminate microorganisms and irradiation using cobalt- 60 is presently the preferred method. Price of irradiation and negative consumers perception are the reason why the irradiation of food is not as widespread compared with conventional methods. Food irradiation up to 10 kGy has been considered as safe and effective. Growing industrial hemp- Cannabis sativa L. subsp. sativa is becoming increasingly popular. The seeds of industrial hemp are used as food and safety standards have to be achived. The aim of this study is to check total mould count and mycobiota composition of two samples of industrial hemp prior and after gamma iradiation at doses 1,3,5,7 and 10 kGy. Samples were serially diluted in peptone water and plated in duplicate onto Dichloran Rose Bengal Chloramphenicol (DRBC) and Dichloran Glycerol (DG18) agar plates. The plates were incubated at 25°C and between 5th and 7th day of incubation the grown colonies were counted. The data were expressed as the number of colony-forming unit (CFU)/g. Upon irradiation at 1, 3, 5, 7 and 10 kGy at dose rate 120 Gy/min, samples were plated onto DG18 and DRBC. The irradiation was performed at panoramic source of cobalt- 60 in Radiation Chemistry and Dosimetry Laboratory of Ruđer Bošković Institute. According to the method described above irradiated samples were plated on DRBC and DG18. CFU/g was checked on 7th, 14th and 28th day. Total mould count was 7.8 x 105 CFU/g (DRBC) and 2.5 x 105 CFU / g (DG18). Natural contaminants of industrial hemp are Fusarium spp., Cladosporium spp. and Alternaria spp. Fusarium spp. and Cladosporium spp. were dominant natural contaminants which comprised approximately 60% of hemp mycobiota. All applied doses of radiation suppressed natural contamination of moulds for more than 90%. Mould count that survived irradiation was between 1500 and 5900 CFU/g which is approximately 0,20 and 0,76% of initial cont. Fusarium spp., Cladosporium spp., Aspergillus fumigatus and Phoma spp. survived irradiation. Dose of gamma radiation up to 10 kGy significantly reduces the number of mould in contaminated samples. For complete elimination of mould it is necessary to irradiate samples with doses above 10 kGy