Utilization of citrus crops processing by-products in the preparation of tarhana

Abstract

After processing of citrus fruits (e.g. lemon, orange, grapefruit, mandarin) for juice and essential oils production, approximately 50% of the original fruit mass is left as waste material. Citrus crops processing by-products are valuable components as they contain nutrients such as pectins, saccharides, carotenoids, some vitamins, minerals, polyphenols and substances with antioxidant activity. Utilisation of these kind of side products in the recipe of various cereal product led to enhancement of final product nutritional value and better sensory attributes as well as improvement of product functional properties. In this work was studied the effect of orange and mandarin dietary fibre application at level 5 and 10% (w/w) in tarhana preparation and the influence on tarhana fermentation process. Chemical analysis showed, that dietary fibre preparations reached higher concentration of ash, fat and total dietary fibre compared to wheat flour. Wheat flour exhibited higher moisture content and protein concentration than citrus dietary fibre preparations. Orange and mandarin dietary fibre preparations showed higher values of water and oil absorption capacity, swelling capacity and least gellation concentration compared to wheat flour. Application of fruit dietary fibre preparations to tarhana recipe caused a rapid decrease in pH from 4.70 - 5.02 to values 4.31 - 4.51 during fermentation process. Reducing saccharides served as an available source of energy for fermenting microbiota and their concentration decreased from 24.5 - 32.8 to 2.2 - 0.2 g/kg after 144 h incubation. Fermentation also led to lactic acid (1.67 - 2.09 g/kg) and acetic acid (1.91 - 2.53 g/kg) production as a consequence of present microorganisms metabolic activity. Sensory evaluation of samples showed, that higher proportion of citrus dietary fibre preparations (10%) negatively affected taste, odour, consistency and sourness. Among all prepared tarhana samples with proportion of citrus dietary fibre preparation was the most acceptable tarhana with 5% of mandarin dietary fibre.