Investigation On Fermentation Technology Of Ice Pear Wine

Hebei province was a large province of pear planting.The further processing of pear was great significance for developing local economy and increasing farmers’income.The purpose of this project was developing a new pear processing variety,ice pear wine.Firstly,the Saccharomyces cerevisiae suitable for brewing Ya pear wine were selected.Based on the study of ice pear wine brewing process.Then the pear residue esters were extracted and used to increase the aroma of the ice Ya pear wine.Finally,the composition changes and stability of ice pear wine during aging were studied.The main conclusions are as follows:1)Screening of Saccharomyces cerevisiae.The"Ya"pear,as the raw material,was squeezed and frozen concentrated into pear juice（ice pear juice）,and then the concentrated juice was inoculated S.cerevisiae and alcohol fermentation happened at low temperature（15℃）.the S.cerevisiae R2 was finally identified as the optimal yeast strain for ice pear wine brewing.The strain R2 had the characteristics of rapid growth,strong sugar-reducing and alcohol-producing capacity and excellent fermentation performances.The ice pear wine had sweet and full-bodied tastes with mellow and elegant fruit aroma,and showed typical flavor of ice pear wine.2)Study on the brewing technology of ice pear wine.The"Ya"pear、"Xue"pear and"Huang Guan"pear,as the raw material,was squeezed and frozen concentrated into ice pear juice,and then the concentrated juice was inoculated S.cerevisiae and alcohol fermentation.Through physical and chemical analysis and sensory evaluation,determination of"Ya"pear are suitable for brewing ice wine.Analysis of residual sugar to taste different ice pear wine,the reducing sugar content of 60⁸0 g/L is to determine the optimal sugar concentration of ice wine.Ice pear wine of approximately 10.5%vol was obtained on optimization conditions that the fermentation time was fifteen days with yeast inoculation of 6.5%,sugar degree of 260g/L,SO₂ dosage of 80mg/L,fermentation temperature of 13℃.The ice pear wine was deeply golden yellow,better coordination of taste,rich floral and fruity,with typical of icewine.The soluble sugar was mainly sorbitol and fructose,the organic acids were malic acid,acetic acid,citric acid and tartaric acid,and the main amino acids were glycine,proline and alanine.The major aroma compounds were ethyl caprylate,isoamyl alcohol,（E）-5-decene-1-alcohol,et al.3)Extraction of esters in Pear residue.Ultrasonic-assisted extraction of ester substances using edible ethanol as solvent was carried out from fresh Ya pear’s residues in this study.Orthogonal experiment was used based on the single factor results to study the effects of ultrasonic power,ultasonic time,solid-to-solvent ratio,extraction temperature,ethanol concentration and vacuum concentration temperature on the extraction of ester substances.The effects of ultrasonic-assisted extraction conditions on the extraction of polyphenols and sugars were also investigated.The results showed that the optimal extraction conditions were ultrasonic power 80 W,ultrasonic time 10 min,solid-to-solvent ratio 1:10,extraction temperature 25℃and ethanol concentration 95%,vacuum concentration temperature 40℃.Under the optimal extraction conditions,extraction yields of esters,polyphenols and sugars were 3815.73μg/g,603.33μg/g and 53.12 mg/g（fresh weight）respectively.The extraction solution was vacuum concentrated at 40℃and 0.1 MPa.The yield of extract concentrate（nutrient and flavour agent of pear）was19.05 g/100 g（fresh weight）,and it contained 16028.34μg/g esters,3104.88μg/g polyphenols and 266.46 mg/g reducing sugars.4)Study on composition changes and stability of ice pear wine during aging.The total acid of ice pear wine decreased by about 12.96%during the aging of 60d.Oxalic acid,tartaric acid,malic acid,acetic acid,citric acid,fumaric acid and succinic acid showed a trend of decline trend in the 90d aging period.Lactic acid increased suddenly after 45⁶0d aging;quinic acid and shikimic acid remained stable during the aging period.During the aging of 60d,the polyphenols and flavonoids of ice pear wine showed a downward trend.The color and lustre of ice pear wine changed significantly during 60d aging.In the aging period,the types of aroma components and contents of ice pear wine were changing,alcohol decreased;esters increased;acids decreased;aldehydes were dynamic;ketones increased;phenolic compounds showed a downward trend;other stable state.The wine precipitate in polysaccharides,polyphenols,flavonoids,reducing sugar,protein and organic acid salt,polysaccharides accounted for the main part.pear wine precipitation protein molecular weight concentrated around 66.2 KDa;ice pear wine protein was very wide band very bright in the vicinity of 31 KDa and 66.2 KDa,the molecular weight of43KDa⁹7.4KDa segment,many bands,and a fuzzy.pear wine precipitation of organic acid salt is mainly L-malate,oxalate and tartaric acid,especially L-malate.