Phytochemical evaluation of black (Morus nigra L. and red (Morus rubra L. mulberries and their potential as functional additives in confectionery industry
The trend of using traditional knowledge and raw materials in food production has been recognised in recent years as a part of the transition from quantity to quality. Autochtonous plant species, often characterized with a highly valuable nutritive and bioactive composition, might be used for the purpose of adding value to food products, thereby improving their functionality and profitability. The consumption of black (Morus nigra L. and red (Morus rubra L. mulberry fruits dates long ago, but they are nowadays poorly utilized due to the extensively managed industrial food resources. The potential of using these raw materials as a starting point for their use in food production as dried ingredients, natural sweetners and even colourants was examined in the present study through the evaluation of their sugars, polyphenolic and anthocyanins content, antioxidative and sensory properties. For the purpose of compositional characterization, high performance liquid chromatography coupled with refractive index detection (HPLC RID) was used to evaluate the contents of sugars, while the phytochemical constituents were assayed spectrophotometrically. To evaluate the potential of using these ingredients in confectionery applications, the fruits were dried by convective (60degC) and freeze drying, and their sensory properties were evaluated by employing quantitative descriptive analysis procedure. Up to 4.7 mg of gallic acid equivalents/g dry matter of total polyphenols in mulberry juice was determined, while flavonoids constitued up to 38% of that content. The content of anthocyanins expressed as cyanidin 3 glucoside equivalents amounted up to 0.06 mg/g dry matter, with a much higher content determined in black mulberry. The ranking of antioxidant properties corresponded to the ranking of total polyphenolic compounds and anthocyanins and exhibited a decreasing tendency from fresh to heat dried fruits. Both black and red mulberry fruits exhibited a favourable sugar composition, since sucrose was not detected, while fructose was the predominant sugar with up to 120 mg/g dry matter determined in black mulberry. Freeze dried black mulberry was generally preferred in terms of the sensory properties, especially taste and texture, with a higher preference of panelists for dried rather than fresh products. The obtained results imply that dried mulberry fruits may be used alone or as functional alternatives in production of other food, especially confectionery products, which is supported by their favourable sugar composition and high polyphenolic antioxidants content.