Comparison of the effect of ultraviolet light, ozone and heat treatment on muesli quality

I. Lignicka*, A. Balgalve, K. Ābelniece and A.M. Zīdere-Laizāne

Felici LLC, Rigas gatve 8, LV-2164, Adazi, Adazu novads, Latvia
*Correspondence: ilva.lignicka@musli.lv

Abstract:

Various muesli processing technologies can be used to lower microbiological parameters. It is necessary to find the best treatment technology to ensure that the product can meet various regulatory limits and to increase the shelf life of the product. The aim of this study was to compare the effect of ultraviolet light, ozone treatment and sterilisation on muesli quality. Muesli samples with dried fruits were tested, comparing the change in total plate count, yeast count and mould count. Short-wave ultraviolet (UV-C) light with a wavelength of 254 nm was used for ultraviolet light treatment, and the product was treated for 1, 2, and 5 minutes. As for ozone treatment, the samples were treated with an ozone concentration of 35 ppm for 30 minutes. Heat sterilisation was performed using sterilisation mode 25-30-50 (heating, holding, cooling), 119 °C, 2.2×10⁵ Pa. Ultraviolet light and ozone treatment did not have a significant impact on total plate count, yeast count and mould count. Heat sterilisation had the most significant effect on muesli sample microorganism level, total plate count, yeast count and mould count level were 10 log cfu g^-1.

Key words:

Wheat straw and lipids: UV-mutagenized Yarrowia lipolytica for the conversion of wheat straw hydrolysate into lipids

D. Atzmüller*+, F. Hawe, D. Sulzenbacher, A. Cristobal-Sarramian+

University of Applied Sciences Upper Austria, School of Engineering, Stelzahmerstraße 23, AT4600 Wels, Austria
*Correspondence: denise.atzmueller@fh-wels.at
+These authors contribute equally to this work

Abstract:

Due to the rising energy demand of our modern society and the finite amounts of petroleum-based fuels, renewable forms of energy have become extremely important. Bio-based fuels like bioethanol and biodiesel represent an already applied and accepted alternative. Biodiesel is currently mainly produced from plant oils. A new and promising alternative, which avoids the use of food crops, is the cultivation of the oleaginous yeast Yarrowia lipolytica, which possesses the capacity to accumulate up to 40% of its biomass in form of lipids. Moreover, this non-conventional yeast is able to metabolize a broad range of carbon-sources, presenting a sustainable alternative to reutilize a wide spectrum of waste substrates. This makes it an auspicious candidate for the generation of non-edible oils for biodiesel production. In this work, we aimed to generate a Y. lipolytica mutant strain with enhanced lipid production when grown on wheat straw hydrolysate as sole carbon source. Therefore, UV mutagenesis was applied and mutants with a high-lipid content were selected by their ability to grow in the presence of the fatty acid inhibitor cerulenin. Further, growth of the mutants on wheat straw hydrolysate was evaluated. The fatty acid composition was analysed by GC-FID and the calculated total lipid content revealed an up to 33% increase compared to the wild type strain. Fermentation optimisation and the combination of various waste substrates as carbon sources are expected to further increase the total lipid yield by the Y. lipolytica mutant strain and serve as initial point for its industrial scale evaluation.

Key words:

biodiesel, UV-mutagenesis, wheat straw hydrolysate, Yarrowia lipolytica