Study On Dry Blueberry Wine And Anthocyanin Extraction From Pomace

Blueberry is rich in nutrients, and has many healthy functions, such as preventing brain aging, promoting a healthy vascular system, fighting inflammation and cancer. FAO recommends it as one of the world's top five healthy fruits. Blueberry planting in China starts late, but develops rapidly. Therefore, technique research of a series of blueberry products is demanded. Even though during the period of planned economy in China, blueberry wine has emerged, generally it is only a complementary product of wine and in a very small scale due to the striction of raw materials. In this research, the effect of yeast strains and fermentation technology on the enological parameters and antioxidant activities of blueberry wine was studied. Further, the solvent extraction and the stability of anthocyanin from pomace were researched. The purpose of this research was to provide the theory basis and study foundation for blueberry wine making. The main results were as follows:1. The main enological parameters and organic and sugar profile of blueberry juice were determined. The results showed that blueberry juice had higher total acidity with 10.27±0.13 g/L expressed as citric acid. Citric acid (9310±259.88 mg/L) was dominant in blueberry juice, accounting for 90% of total acidity. Following it were gluconic acid (4838.18±121.10 mg/L), malic acid (103.1±2.87 mg/L), oxalic acid (35.5±3.12 mg/L), ascorbic acid (19.4±0.69 mg/L) and fumaric acid (0.58±0.02 mg/L). The content of total sugar was 79.94±1.05 g/L with almost equal glucose and fructose.2. The main influencing factors of glycerol production in fruit wine were studied. The results showed: (1) The glycerol yield of different yeast strains had significant difference (P<0.01), ranging between 4.42±0.02 g/L and 6.18±0.07 g/L. (2) Generally, glycerol yield by six yeasts in the fermentation temperature of 20℃was higher than 15℃. However, the effect of temperature on Y2 was not significant (P2>0.05); (3) The effect of addition of 100 mg/L DAP was significant for yeasts Y1, Y2, Y3 and Y4 (P<0.05) which produced more glycerol. However, the addition of 100 mg/L DAP enabled Y5 produce significant less glycerol, and the effect on Y6 was not significant (P6>0.05). (4) Generally, the apple wine added in 150 mg/L SO₂ contained more glycerol than 100 mg/L SO₂. However, the differences of glycerol production by Y1, Y3 and Y6 were not significant (P>0.05) and glycerol yield by Y5 had significant decrease (P5<0.05).(5) The pear juice added in 100 mg/L SO₂ and with no DAP was introduced six yeasts and then fermented in the temperature of 15℃to make pear wine. With the same yeast strain, the pear wine had significant more glycerol (P<0.05) than apple wine with the same conditions.3. Blueberry wine maked with six yeasts in the fermentation temperature of 20℃was analysed. Because of the shorter fermentation periods (23 d), higer glycerol level (9.74 g/L) and best sensory qulity of the wine fermented with Y5, Y5 was chosen as the blueberry wine making yeast strain.4. Blueberry wine was made with Y5 in two fermentation process: fermented with (BW2) or without (BW1) pomace and two kinds of pomace (BP1 from BW1 and BP2 from BW2) were obtained. The results showed that there was considerable loss of anthocyanins (40% for BW1, 67% for BW2) and total phenolics (31% for BW1, 46% for BW2) during alcoholic fermentation and the degradation rate of anthocyanins was higher than phenolics. The BW1 had higher content of anthocyanins, total phenolics, higher ferric reducing/antioxidant power (FRAP) and antiradical activity (DPPH) than BW2, and the same pattern to BP1 than BP2. Correaltion analysis showed that the FRAP and DPPH free redical scavenging activity had significant linear relationship with the content of total phenolics (r (xy) = 0.999, P < 0.01). However, the correlation with anthocyanins was not significant (r (xy) = 0.539,P = 0.461>0.05). Aprart from the organic acids in blueberry juice, the blueberry wine also contained pyruvic acid, lactic acid, acetic acid and succinic acid. After fermentation, contents of citric acid, gluconic acid and ascorbic acid decreased, and oxalic acid was not detected in blueberry wine. Excepting small amout of fructose, glucose, rhamnose xylose/arabinose and sucrose, other unfermented sugar was not detected.5. The extraction conditions from the blueberry wine pomace were optimized and the stability of the pigment as a kind of food additive was studied. The results showed that the maximum absorption wavelength of the pigment was 520 nm. The optimum conditions of the extraction were as follows: the ethanol content 70%, the ratio of dry pomace to extracting solution 1:25, the extraction period 60 min, extraction temperature 70℃. Under the optimum conditions, 6.26 mg anthocyanin could be obtained from 1g pomace. The colour intensity of pigment solution decreased greatly with the increasing of pH value. The pigment solution showed certain thermal stability and was sensitive to VC, oxidant (Peroxide), reducer (Sodium Sulfite), preservative (Sodium Benzoate) at room temperature. The pigment solution was not stable with exposure to outdoor light, but it was not affected by sucrose and glucose solution.