Enhancing fermentation of non-Saccharomyces cerevisiae by adding gum arabic

Non-Saccharomyces cerevisiae has been used to greatly improve the nature of wine during fermentation, due to the high yield of glycerol, lactic acid, higher alcohols and aromatic esters. But it is lacking on the better fermentation in the whole process of alcohol production. Therefore, much attention has also gained on the non-Saccharomyces cerevisiae in the wine industry at present. The previous research has focused mainly on non-Saccharomyces cerevisiae mixed fermentation with Saccharomyces cerevisiae. Only a few studies can be found on its pure fermentation. This study aims to explore the promoting effect of the gum arabic on the fermentation of Lachancea thermotolerans and Torulaspora delbrueckii in wine fermentation. The fermentation of non-Saccharomyces cerevisiae was also enhanced after addition. Taking Lachancea thermotolerans A38 and Torulaspora delbrueckii R12 as the objects, the simulated and grape juice was fermented to add the different concentrations of gum arabic before fermentation. The wine samples without gum arabic were taken as the control. The reducing sugar, organic acid, phenolic substances, color, aroma and sensory of wine samples were measured after brewing. Firstly, the reducing sugar of the sample was determined during fermentation. The fermentation of the simulated and grape juice was completed within 20 days. There was the accelerated fermentation rate of the samples with the gum arabic. The fermentation ability of A38 and R12 was improved at the concentration of 10%, whereas, the residual reducing sugar was low at the end of fermentation. The cell immobilization that caused by the addition of gum arabic was promoted the tolerance of yeast to the high substrate concentrations, while reduced the adverse effects of external conditions on yeast, thereby promoting the fermentation. In terms of other physical and chemical indicators, the addition of gum arabic was also promoted the glycerol and ethanol substances. In the fermentation of grape juice, the ability of A38 to produce the glycerol was stronger than that of R12. The high yield of lactic acid reached 2.2 g/L during fermentation. It also shared the advantage of reducing acetic acid. A systematic measurement was performed on the color and phenolic content of the wine samples. The content of anthocyanins gradually decreased with the increase of gum arabic concentration, due to the adsorption of gum arabic. The lowest content of tannin was found in the fermentation of grape juice, when the concentration of gum arabic was 10%. A total of 47 volatile aroma substances were detected in the samples using aroma analysis. Once the concentration of gum arabic was 2.5%, the contents of esters, alcohols and terpenes in the samples increased significantly, such as ethyl acetate, ethyl lactate, n-butanol, and isoamyl alcohol. These substances were greatly contributed to the strong floral and fruity aroma in wine. The addition of arabic gum was utilized to clarify the wine sample during sensory evaluation. Furthermore, the high concentration of arabic gum was hindered the formation or release of flower and fruit aroma substances in the sample. Once 10% concentration of arabic gum was added, the lower score of aroma index was observed in the wine sample, compared with the 2.5% concentration of arabic gum or without. In terms of taste, the 2.5% concentration of arabic gum was also enhanced the esters and alcohols in the wine sample. As such, the aroma was enriched to enhance the structure of the wine sample. In summary, the addition of gum arabic was significantly promoted the fermentation of A38 and R12. The residual reducing sugar at the end of fermentation of grape juice was significantly reduced by 36.84 g/L compared with control.The high fermentation rate was obtained at the addition concentration of 10%. The residual reducing sugar was significantly lower than that of the control sample. There were the higher contents of esters, alcohols and terpenes in the wine samples with 2.5% Arabic gum, compared with the control. The better sensory score was observed in the more abundant fruit aroma of the samples. At the same time, the addition of gum arabic also increased the content of glycerol and ethanol in the sample. The fuller wine body was realized to reduce the unpleasant substances, such as the acetic acid. The content of lactic acid was promoted in the wine sample using heat-resistant Lachancea thermotolerans and Torulaspora delbrueckii. Higher concentrations of gum arabic also shared a negative impact on the sensory quality of wine. Therefore, the arabic gum can be expected to enhance the fermentation of Lachancea thermotolerans and Torulaspora delbrueckii in wine production. The finding can also provide an effective solution for the fermentation of non-Saccharomyces cerevisiae in wine production.