This study was conducted to investigate nutritional and functional components of mulberry fruits from different mulberry(Morus alba L.) cultivars, and their quantitative changes of physicochemical properties and functional constituents of the mulberry processed foods according to the drying, concentration, fermentation, and aging for preparation of high quality mulberry processed products, such as mulberry dry fruits, juices, wines, and vinegars. Additionally, quality specifications of high quality mulberry processed foods and other mulberry processed foods available in the market were also made.
Physiochemical properties, nutritional and functional components of mulberry fruits were investigated according to four different mulberry cultivars, including Iksuppong, Daeseongppong, Cheongilppong, and Gwasang 2. Among four mulberry cultivars examined, Iksuppong, Cheongilppong and Gwasang 2 had higher contents of sugar and total soluble solid than other mulberry cultivars, while contents of protein, fat, fiber and titratable acidity had lower contents. Daeseongppong had the highest content of total anthocyanin(1.16 g/100 g), total phenol(2.23 g/100 g), and total flavonoid(0.79 g/100 g), while Gwasang 2 and Iksuppong had lower contents than other cultivars. Daeseongppong had higher contents of two major anthocyanins, C3G(846.49 mg/100 g) and C3R(490.12 mg/100 g), while Cheongilppong had lower contents of two anthocyanins than other mulberry cultivars. Daeseongppong of four mulberry cultivars had the highest flavonoid(PC 14.02 mg/100 g, RT 164.47 mg/100 g, IQ 35.21 mg/100 g, QC 98.18 mg/100 g) and resveratrol(5.04 mg/100 g) contents, followed by Gwasang 2(PC 9.59 mg/100 g, RT 310.61 mg/100 g, IQ 31.44 mg/100 g, QC ND, t-Res 1.31 mg/100 g) > Cheongilppong(PC ND, RT 59.04 mg/100 g, IQ 10.95 mg/100 g, QC 24.32 mg/100 g, t-Res 2.35 mg/100 g) > Iksuppong((PC ND, RT 59.04 mg/100 g, IQ 17.40 mg/100 g, QC 24.27 mg/100 g, t-Res 2.30 mg/100 g) in a descending order. Daeseongppong(260.91 mg% & 33.71 mg%) had the highest GABA and DNJ content, followed by Iksuppong(225.54 mg% & 29.79 mg%) > Cheongilppong(232.57 mg% & 9.92 mg%) > Gwasang 2(163.75 mg% & 33.01 mg%), in descending order.
Freeze-dried mulberry fruits had higher contents of functional constituents, while hot-air dried mulberry fruits had higher palatability including taste, flavor, color than freeze-dried mulberry fruits. Additionally, a freeze-concentrated mulberry juice had higher quality characteristics on functional constituents and palatability than heat-concentrated mulberry juice. Meanwhile, mulberry syrups prepared by mixtures of sugar and oligosaccharide had higher quality characteristics on functional constituents, microbes and palatability than mulberry syrups prepared by only a sugar. Especially, mulberry syrups prepared by a combined treatment(mulberry fruit: sugar: oligosaccharide(100:70:30, g/g) of sugar and oligosaccharide had the highest quality characteristics about functional constituents, microbes and palatability. On the other hand, three different mulberry wines, such as dry wine, semi-sweet wine, and ice wine, were prepared by a freeze-concentration method of squeezed ‘Iksuppong’ mulberry juice. Mulberry dry wine was made by adding sugar and yeast by a conventional fermentation method, while the semi-sweet wine and ice wine were prepared by freeze-concentration of squeezed mulberry juice to 24 ?Brix and 35 ?Brix, respectively. Among three mulberry wines, ice wine showed the greatest functional constituents, including polyphenols, moracins, GABA and DNJ, and highest palatability including color, taste, and flavor, as well as higher biological effects, including antioxidant, anti-aging, and anti-diabetic activities. Finally, high quality mulberry vinegar with higher titratable acidity(6∼7%) and palatability were prepared by using the fermented mulberry wine(6% alcohol) inoculated with Acetobacter spp.. In addition, it was found that the fermented mulberry wine and mulberry vinegar had dihydroquercetin as a functional biomarker with anti-diabetic, anti-aging, and antioxidant activities, and good esterified flavor, phenylethylacetate, by chemical analysis of LC-MS and GC-MS. Thus, the manufactured technology of high quality mulberry processed foods, such as mulberry syrup, mulberry wine, and mulberry vinegar were developed through chemical analysis of functional constituents and palatability during a drying, freezing concentration, fermentation and aging processes of mulberry fruits. Finally, quality specifications of mulberry processed foods, such as mulberry syrup, wine, and vinegar, were established by chemical analysis of physicochemical characteristics, functional markers, and evaluation of biological activities. Quality specification of each mulberry processed food were as follows; mulberry syrup(soluble solid; 40∼60 °Brix, acidity; 0.2∼0.5%, pH: 3.0∼4.5, colorimetry; L value 40∼60, a value 10∼15, b value 10∼15, biomarker; DQ, QT 5∼30 mg/L), mulberry wine(Alcohol; 10∼13%, acidity; 0.2∼0.8%, pH: 4.5∼5.0, colorimetry; L value 38∼45, a value 35∼40, b value 30∼35, biomarker; PC 5∼20 mg/L, DQ, 20∼80 mg/L), and mulberry vinegar(alcohol: <1%, acidity; 6∼7%, biomarker; PC, DQ, DK, QT 1∼10 mg/L).
These results provide an basically useful informations to food technologist for development and standardization of high quality mulberry processed foods, such as dried mulberry fruits, mulberry juice, and mulberry syrup, wine and vinegar. Particularly, quality specification of several high quality mulberry processed foods established by chemical analysis of physicochemical characteristics, functional biomarkers, and palatability, as well as evaluation of their biological activity were widely used as a referred guide material of mulberry processed food company. Scale-up and manufacturing of high quality mulberry processed foods, and development of functional mulberry foods are now in progress.