Effects of gamma radiation on physicochemical, thermogravimetric, microstructural and microbiological properties during storage of apple pomace flour

The effects of gamma radiation on the physicochemical, thermogravimetric, microstructural and microbiological properties of apple pomace flour were evaluated for a period of nine months storage. Calcium levels were higher in the irradiated samples. The irradiated samples remained stable during storage regarding the contents of protein, lipids, total dietary fibre, total reducing sugars, potassium, zinc, iron and manganese. The chemometric approach enabled a better visualisation of the samples. The results were not influenced by the effect of gamma radiation during storage. The thermogravimetric curves showed four major mass losses in consecutive reactions. The photomicrographs showed a composite of organic and heterogeneous material, with agglomerated particles with irregular shapes and sizes. For the microbiological analysis at a dose of 1 kGy, the presence of moulds occurred at 9 months of storage, however, the levels were below the indicative tolerance and for 2 kGy there was no contamination of yeasts and moulds. (C) 2016 Elsevier Ltd. All rights reserved.