1. INTRODUCTION
Cayratia trifolia (L.) Domin is an uncultivated glabrous tendril climber widely distributed in a bunch of bushes or glade areas of Asia such as Vietnam, Cambodia, Indonesia, India, China, Africa, and Australia. Numerous studies highlight the rich bioactive compounds in three-leaf Cayratia, contributing to antioxidant, anticancer, and anti-inflammatory properties [1,2]. In Vietnam, it is used as an ingredient in traditional cuisine, medicine, and winemaking particularly in Ca Mau and Kien Giang provinces. Cayratia wine was produced and commercialized following a traditional fermentation method for years which has the color as red-grape wine. In 2018, it was surveyed a completed winemaking process from raw material to final product using thermotolerant yeast sources isolated from three-leaf Cayratia berry [3-5].
The food fermentation industry is experiencing robust growth, marked by significant transformations driven by advancements in scientific technologies over the decades. Particularly, the exploration of yeast diversity underscores the crucial role of isolating novel strains for various applications in food fermentation, spanning wine, beer, pickles, bread, and cider. In this context, 20 yeast strains were isolated from six traditional marchas, microbial starters used in amylolytic fermentation, located in Sikkim, India. This initiative reflects the industry’s commitment to harnessing microbial diversity for enhanced and diversified fermentation processes [6]; for instance, 21 Saccharomyces strains were found during cider production [7]; 2 thermotolerant yeasts were reported to have a high-temperature limit of 47°C among the total of 34 strains isolated from Indonesian rice wine [8]. In addition, yeasts were also isolated from different kinds of fruit such as watermelon [9], Cayratia berry [10], dragon fruit [11], Gemlik olives [12], and soursop [13,14].
The inclusion and diversification of yeast in food fermentation highlight the distinct capabilities of each strain in alcoholic beverage production under varied optimal conditions. For instance, Saccharomyces cerevisiae FBY015, sourced from soursop, efficiently yields 10% ethanol soursop wine within 12 days at room temperature [14]. In contrast, S. cerevisiae VK1 achieves natural fermentation of pineapple wine in just 5 days at room temperature [15]. The thermotolerant strain S. cerevisiae Y8 exhibits remarkable fermentability, producing 7.45% (v/v) and 4.18% (v/v) ethanol content in pineapple wine at 37°C and 40°C within 5 days, respectively [16]. Candida hellenica, Pichia anomala, and Candida pelliculosa demonstrate resilience to high salt and low pH in brine natural fermentation media, facilitating olive fermentation within the temperature range of 15–28°C [3]. These findings underscore the tailored contributions of diverse yeast strains to alcoholic beverage production across different temperature and substrate conditions.
In the previous studies, 151 strains were found from Cayratia berries, in which, 57 thermotolerant yeasts were selected for winemaking at 37°C [5]. Cayratia wine was fermented using S. cerevisiae HG1.3 to produce an ethanol content of 9.9% v/v [3], and 12% v/v at 35°C in a 6-day incubation time [17]. Despite the growing global and Vietnamese preference for low-alcohol fruit drinks over traditional wines, it is necessary to develop the fermentability of S. cerevisiae HG1.3 for the production of low-alcoholic beverage products. Cayratia, a wild ingredient with a distinct purple color, is rich in polyphenols with antioxidative properties. Consequently, the authors aim to develop a fruit cider product with elevated polyphenol content and biological activity, diverging from traditional grape-based products. Using three-leaf Cayratia berries. Even wine production is better at low temperatures; this result reveals the prospect of wine production at high temperatures by S. cerevisiae HG1.3 is also suitable for the tropical countries like Vietnam.
2. MATERIALS AND METHODS
2.1. Materials
Cayratia berries were purchased at local markets in An Giang, Kien Giang, Can Tho, Hau Giang provinces, Vietnam. The raw material was chosen as juicy, shiny, ripe, uncrushed ones, and immediately transferred to the laboratory. S. cerevisiae HG1.3 was isolated and stored at the microbial biotechnology laboratory, Institute of Food and Biotechnology, Can Tho University, Vietnam [13]. Sucrose (>99.7%) was produced by Bien Hoa sugar company, Dong Nai, Vietnam. Citric acid, calcium carbonate (CaCO3), sodium bisulfite (NaHSO3), ethanol, peptone, yeast extract, and D-glucose were purchased from Xilong, China. Folin-Ciocalteu’s phenol reagent was produced by Sigma-Aldrich.
2.2. General Procedure of Cayratia Cider Fermentation
Shiny, juicy, and dark black ripe Cayratia berries were collected in the provinces of the Mekong Delta, in Vietnam. These fresh berries were washed under tap water, then, rinsed with distilled water and drained for an hour until the fruit’s surface dried. Thereafter, 1000 g of Cayratia berry was pressed by a juicer and filtered through a filter cloth to collect 740 mL of juice. The juice was then diluted with water to a ratio of 1:1 (v/v) and adjusted to the appropriate pH value and TSS using 1 mol/L sodium carbonate and 0.5 mol/L citric acid. The adjusted Cayratia juice was fermented at room temperature (28 ± 2°C) using S. cerevisiae HG1.3 for 72 h after being sterilized with NaHSO3 (140 mg/L for 2 h). The product was sterilized at 75°C in 15 min and allocated into 250 mL glass bottles for quality evaluation. The fermentation process is summarized in Figure 1. (Supplementary document, Figure S1).
![]() | Figure 1: The procedure of Cayratia cider fermentation. [Click here to view] |
S. cerevisiae HG1.3 was isolated from Cayratia berries and performed high fermentation ability [3,5,10]. A single colony was added to 100 mL YPD broth which had been sterilized at 121°C for 15 min, then was shaken at room temperature (28 ± 2°C) to obtain a rate of 108 cells/mL. Subsequently, the addition of 0.3% S. cerevisiae HG1.3 was inoculated to Cayratia juice for fermentation.
2.3. Effects of the pH Values and TSS on Cayratia Cider Production
Cayratia juice was diluted into water with a ratio of 1 to 1, adjusted to the total soluble solids (TSS) 18, 20, 22, and 24 Bx; pH 3, 4, and 5, respectively. To the juice mixture, 0.3% (w/v) S. cerevisiae HG1.3 was added to incubate at 28 ± 2°C (room temperature) for 72 h. After fermentation, the product was filtered, sterilized, and allocated into 250 mL glass bottles for further evaluation.
2.4. Effects of Yeast Content and Fermentation Times on Cayratia Cider Production
The initial pH values and TSS of Cayratia juice were selected from the above experiment. S. cerevisiae HG1.3 was supplemented to the juice with a ratio of 0.1; 0.15; 0.2; and 0.25% (w/v) and fermented at 28 ± 2°C for 24, 48, and 72 h, respectively. The product was filtered, sterilized, and allocated into 250 mL glass bottles for the next experiments.
2.5. Physicochemical Analyses
Dark black ripe Cayratia berries were removed stalk and washed under tap water, thereafter, the juice was collected using a juicer (Philips HR1811, Netherlands). The pH value was measured using a digital pH meter (Hanna, America), and the (TSS, °Bx) were measured using a manual Atago refractometer (0–33 °Bx, France). Ethanol content (% v/v) at 20°C was determined using the distillation method.
The total phenolic content was determined by the Folin-Ciolcateau method as follows: 1.25 mL folin solution (10% v/v) was added to 0.5 mL methanol-caryatid juice solution (60 μg/μL) and incubated for 5 min. Then, the mixture samples were reacted with 1 mL Na2CO3 (2% w/v) for 45 min in the dark. The optical density was measured at 760 nm [4].
2.6. Microbiological and Sensory Analyses
The microbiological parameters were conducted by the National Agro-Forestry Fisheries Quality Assurance Department – Branch 6 (Cantho City, Vietnam). Cayratia cider was analyzed for microbiological and chemical quality parameters: total microaerophile (CFU/mL), total yeast and mold (CFU/mL), Clostridium perfringens (CFU/mL), Coliforms (CFU/mL), and E. coli CFU/mL) according to International Organization for Standardization [18]; methanol and ethanol content according to Association of Official Agricultural Chemists [19]. Sensory evaluation of wine in the criteria of clarity and color, aroma, taste, and overall confidence was done according to Vietnam National Standard 3217:79 [20].
2.7. Statistical Analysis
All the experiments were performed in triplicate. The data were analyzed using Statgraphics Centurion version XIX-X64 (Statpoint Technologies Inc., USA) and Excel 2016 software (Microsoft Inc., USA).
3. RESULTS AND DISCUSSION
3.1. Physicochemical Characteristics of the Juice
Due to the appropriate taste, flavor, availability, high sugar, and water content, and overall chemical composition, numerous fruits are cultivated and selected for winemaking throughout the world. Cider, non-grapefruit wine, is fermented from temperate fruits or tropical fruits such as apples, berries, cherries, kiwifruit, plums, peaches, strawberries, mango, jackfruit, banana cashew apple, pineapple, watermelon, and wild apricot. Physicochemical analysis of fruit juice is an initial important step during the cider fermentation process to evaluate fruit characteristics. As of the results of physicochemical analyses [Table 1], Cayratia berry had a low content of TSS and pH, dragon fruits 11.8 °Bx [21], however, high concentration of total phenolic compounds.
Table 1: The pH value, TSS, and total phenolic content of Cayratia juice.
Criteria | Mean±SE |
---|---|
pH | 3.2 |
Soluble solid content (°Bx) | 6.0 |
Cayratia juice volume (L/kg) | 0.74±0.05 |
Total phenolic content (mgGAE/g) | 18.89±0.04 |
Anthocyanin content | 0.62±0.02 |
SE: Standard error, TSS: Total soluble solids.
3.2. TSS Content and pH Value of Cayratia Cider Production
In this study, the pH value and TSS of Cayratia juice were determined at 3.2 and 6 °Bx, respectively; however, a TSS of 20 °Bx and pH below 4 is recommended for cider production [22]. It must be adjusted, therefore, an optimal pH and TSS for yeast’s activity during the fermentation process to produce a good quality Cayratia cider. A high concentration of polyphenol Cayratia wine, 11.68–12.0% v/v ethanol, was fermented by S. cerevisiae HG1.3 at conditions (35°C, pH 4.5, 20 °Bx, 105 cells/mL, 6 days) [5,17]. On the other hand, cider is one of the low alcoholic drinks (0.5–6.5% v/v alcohol) [23]. According to Huan, the optimal conditions of fermented dragon fruit juice were selected as 18 °Bx, 2% yeast inoculation rate, and 44 h incubation time to produce 3.54% v/v alcohol dragon fruit drink with remaining sugar content of 14.6 °Bx [21]. Similarly, S. cerevisiae produced 5.2% v/v alcoholic Docynia indica juice at 18 °Bx of initial TSS [24]. Based on these findings, pH of 3, 4, 5 and TSS of 18, 20, 22, and 24 °Bx were selected to optimize the Cayratia cider fermentation process, the effect of factors on ethanol content is presented in Table 2. The lowest ethanol content was 3% v/v produced in treatment 4 (pH 3, 20 °Bx) and 10 (pH 3, 24 °Bx), whereas the highest ethanol content was 5% v/v created in treatment 6 (pH 5; 20 °Bx) and 8 (pH 4; 22 °Bx). Meanwhile, the ethanol content in treatments 2, 5, 7, and 9 is not significantly different at the 95% confidence level (P < 0.05).
Table 2: Effects of pH and TSS on ethanol content.
Treatment | Factors | Results after fermentation | |||
---|---|---|---|---|---|
pH value | TSS (°Bx) | pH value | TSS (°Bx) | Ethanol (% v/v) ð 20°C | |
1 | 3 | 18 | 2.00 | 11.30 | 3.16c |
2 | 4 | 18 | 2.49 | 11.30 | 4.66ab |
3 | 5 | 18 | 4.05 | 11.70 | 3.66bc |
4 | 3 | 20 | 2.09 | 13.67 | 3.00c |
5 | 4 | 20 | 2.84 | 13.33 | 4.66ab |
6 | 5 | 20 | 3.88 | 13.67 | 5.00a |
7 | 3 | 22 | 2.07 | 14.33 | 4.66ab |
8 | 4 | 22 | 3.13 | 14.67 | 5.00a |
9 | 5 | 22 | 4.04 | 14.33 | 4.66ab |
10 | 3 | 24 | 2.15 | 15.33 | 3.00c |
11 | 4 | 24 | 3.18 | 15.33 | 4.00abc |
12 | 5 | 24 | 4.12 | 15.67 | 4.33ab |
P=0.0000 | P=0.0001 | P=0.0036 |
The values in this table were the average values of triplication. The average values in a group with the same letter were not significantly different at the 95% confidence level (P<0.05), TSS: Total soluble solids.
Yeast growth is affected by osmotic stress due to the high sugar concentration, as well as low pH during winemaking. The pH value and TSS decreased after fermentation, the highest pH and TSS were 4.12 and 15.67 °Bx, and the lowest pH and TSS were 2.00 and 11.30 °Bx, respectively. The logarithmic concentration term, pH, displays hydrogen ion activity which plays an important role in winemaking. Its involvements range from physicochemical and biological concerns to sensory properties and potential defects. Yeast could grow in an environment of pH 2.0–8.0 but optimized in pH 4.0–6.0, depending on temperature, the presence of oxygen, culture, and the strain of yeast [25]. A low initial pH prolongs the yeast lag phase which leads to an effect on accumulating mass loss, changes in total sugar consumption rate, increase of final acetic acid and glycerol content, and decrease of final ethanol [26]. This could be seen that when the initial pH is decreased from 4 to 3, the ethanol content was significantly reduced by about 1% v/v. In addition, the results on the influence of initial pH showed a significant difference in sensory quality at the 5% level. A pH value in the range of 4 resulted in a better sensory quality of the product in terms of color (86%), aroma (84%), and taste (82%). At pH values of 3 and 5, the resulting products showed no significant sensory differences and were even quite similar in terms of aroma and taste [Figure 2a, Supplementary information, Table S1].
![]() | Figure 2: The effect of pH and total soluble solids on Cayratia cider sensory charts. (a) pH effect on clarity and color, taste, and aroma of Cayratia cider. (b) pH effect on clarity and color, taste, and aroma of Cayratia cider. (Sensory attributes including clarity and color, taste, and aroma were evaluated using a 5-point Hedonic scale (where 1 = dislike extremely, dislike = 2, neither like nor dislike = 3, like = 4, and 5 = like extremely) following Vietnam National Standard TCVN 3215-79 by 50 panelists selected from professors, graduate and undergraduate students, staff, and faculty of several related departments in Can Tho University of Technology. [Click here to view] |
At present, the addition of sugar to fermenting and the finished wine is permitted in the wine industry. Sugar is generally used in the form of concentrates, dry dextrose, sucrose, or syrups of the latter two. However, the sugar concentration can inhibit yeast growth and decrease the maximum population, which affects ethanol production. Herein, the remaining sugar resulted similarly in the final products fermented at the same initial TSS but with different pH values. It also showed that, however, the higher Bx level before fermentation was, the more Bx level after fermentation was obtained. In detail, around initial 11 °Bx of remaining sugar was found in the final products started with TSS 18 °Bx, similarly to other ones, fermentation environments of 20, 22, and 24 °Bx resulted in 13, 14, and 15 °Bx of fermented products, respectively. Nevertheless, ethanol content was reduced in high sugar concentration, and no significant change (5% v/v ethanol of fermented product) when the initial TSS increased from 20 to 22. Yeasts use glucose and fructose as carbon and energy sources to grow; therefore, it would be in nutrient storage to increase biomass if the initial TSS was too low. In contrast, the addition of too much sugar would hinder yeast activity due to increased osmotic pressure, unbalancing the physiological state and metabolism of yeast, and leading to a reduction of ethanol content [27].
Furthermore, the effect of initial sugar concentration on color and clarity, aroma, and taste was significantly different at the 5% statistical level (P < 0.05). Particularly, at 22 °Bx, the sensory quality of the product was the highest of others, approximately 88% with 4.3 points [Figure 2a and b]. The 18 °Bx treatment had the lowest sensory evaluation than that of, followed 20 and 24 °Bx treatments, respectively [Supplementary information, Table S2]. Consequently, pH 4 and TSS 22 °Bx were selected for further experiments to optimize Cayratia cider fermentation.
3.3. Yeast Inoculation Level and Fermentation Time of Cayratia Cider Production
Low alcoholic beverages could be produced by many modifications involving one or more fermentation methods, shorter processing times, and lower temperatures to reduce the final ethanol concentration [23]. In this study, low alcoholic Cayratia cider fermentation was optimized with yeast inoculation levels (0.1, 0.15, 0.2, and 0.25% w/v) at 28 ± 2°C in 24, 48, and 72 h, respectively. The results are illustrated in Table 3 with a 95% confidence level, (P < 0.05).
Table 3: Effects of yeast inoculation levels and time fermentation on ethanol content.
Treatment | Factors | Results after fermentation | |||
---|---|---|---|---|---|
Yeast inoculation (% w/v) | Time (h) | pH value | TSS (°Bx) | Ethanol (% v/v) at 20°C | |
1 | 0.10 | 24 | 3.80 | 21.7 | 0.0e |
2 | 0.10 | 48 | 3.13 | 15.0 | 1.3d |
3 | 0.10 | 72 | 2.96 | 15.0 | 2.6b |
4 | 0.15 | 24 | 3.90 | 21.3 | 0.0e |
5 | 0.15 | 48 | 3.34 | 14.7 | 2.0c |
6 | 0.15 | 72 | 3.09 | 15.0 | 3.0b |
7 | 0.20 | 24 | 3.94 | 21.7 | 0.0e |
8 | 0.20 | 48 | 3.31 | 14.3 | 1.6cd |
9 | 0.20 | 72 | 3.04 | 14.7 | 4.6a |
10 | 0.25 | 24 | 3.97 | 21.3 | 0.0e |
11 | 0.25 | 48 | 3.51 | 14.7 | 2.0c |
12 | 0.25 | 72 | 3.27 | 14.7 | 4.5a |
P=0.0001 | P=0.0000 | P=0.0001 |
The values in this table were the average values of triplication. The average values in a group with the same letter were not significantly different at the 95% confidence level (P<0.05), TSS: Total soluble solids.
During fermentation, the yeast uses sugar for growth, which is converted into ethanol and carbon dioxide in the fruit juice when the process is fulfilled. According to the results, Bx level and pH value reduced after 24–72 h of incubation time, the more fermentation time is prolonged, the more ethanol is produced. The lowest ethanol content is 0% v/v produced at a fermented environment of 0.1% and 0.25% w/v in 24 h. On the contrary, the ethanol content fermented for 72 h was higher than that of, and highest at 0.2% and 0.25% w/v yeast concentration but not significantly different at 95% confidence (4.6 and 4.5% v/v ethanol, respectively).
Moreover, sensory quality evaluation achieved the highest clarity and color, taste, and aroma value with points of 5.0, 4.9, and 5.0, respectively, fermented for 72 h at 28 ± 2°C with 0.2% inoculation yeast level [Figure 3]. Cayratia cider sensory quality affected by yeast ratio and fermentation time was evaluated by 50 members. At the yeast ratio of 0.2%, it is appreciated with the highest score in terms of clarity and color, 86% (4.3/5), aroma 86% (4.3/5), and taste 86% (4.3/5) [Supplementary information, Table S3]. For the fermentation time effect, all 50 members agreed that the 72-h treatment had good sensory quality with 84% clarity and color (4.2/5), 82% aroma (4.1/5), and 82% taste (4.1/5) [Supplementary information, Table S4]. These results are found consistent with the studies on the cider made from King orange (Citrus nobilis L. Osbeck) and soursop fruit (Annona muricata L.) [28,29].
![]() | Figure 3: The effect of yeast inoculation level and fermentation time on Cayratia cider sensory chart. (Sensory attributes including clarity and color, taste, and aroma were evaluated using a 5-point Hedonic scale (where 1 = dislike extremely, dislike = 2, neither like nor dislike = 3, like = 4, and 5 = like extremely) following TCVN 3215-79 Vietnamese standard by 50 panelists selected from professors, graduate and undergraduate students, staff, and faculty of several related departments in Can Tho University of Technology). [Click here to view] |
3.4. Microbiological and Chemical Evaluation of Cayratia Cider
Food safety is always an important factor in the food industry. The quality of the product on microbiological and chemical criteria was conducted by the National Agro-Forestry Fisheries Quality Assurance Department - Branch 6, Vietnam. The results are shown in Table 4, followed by Vietnam National Standard QCVN 6-3:2010/BYT. The final product is presented as in Figure 4 and analysis results are shown in Table 4. The cider produced meets the Vietnamese standard requirements with 4.62% (v/v) ethanol content, and the absence of methanol, Coliforms, E. coli, and C. perfringens, while the total microaerophile, yeast, and mold of Cayratia cider were acceptable based on the requirements of microbiological safety standards [Table 4].
Table 4: Quality evaluation of Cayratia cider.
Criteria | Vietnam National Standard QCVN 6-3:2010/BYT | Method | Result |
---|---|---|---|
Total microaerophile (CFU/mL) | 1,000 | ISO 4833-1:2013 | <1 |
Total yeast and mold (CFU/mL) | 100 | ISO 215227-2:2008 | <1 |
Coliforms (CFU/mL) | Abs | ISO 4832:2006 | 0 |
E. coli (CFU/mL) | Abs | ISO 16649-2:2001 | 0 |
Clostridium perfringens (CFU/mL) | Abs | ISO 7937:2004 | 0 |
Methanol (%) | Abs | Ref.AOAC 972.11 (LOQ=0.025%) | nd |
Ethanol (% v/v) | Ref.AOAC 972.11 (LOQ=0.025%) | 4.62 |
National Agro-Forestry Fisheries Quality Assurance Department - Branch 6, Vietnam. Wherein, abs: absence; nd: not detected.
![]() | Figure 4: Cayratia cider. [Click here to view] |
4. CONCLUSION
Fermented Cayratia cider successfully produced 4.6% (v/v) ethanol content by S. cerevicsiae HG1.3 at room temperature 28 ± 2°C with initial TSS of 22 °Bx, pH 4, and inoculation yeast rate of 0.2% w/v. In general, Cayratia cider has a purple color, clear, and favorable taste and aroma which meets the Vietnamese standards for sensory quality as well as microbiological and chemical quality. Therefore, Cayratia cider will be a potential new product in the fermented food industry in Mekong Delta in particular, and Vietnam in general.
5. AUTHOR CONTRIBUTIONS
Concept and Design: Doan T.K. Tien, Nguyen H. Thanh, Le T.B. Son, and Nguyen N. Thanh. Data Acquisition: Nguyen H. Thanh, Le T.B. Son, and Nguyen N. Thanh. Data Analysis/Interpretation: Huynh T.N. Mi, Nguyen H. Thanh, Le T.B. Son, Nguyen N. Thanh, and Huynh X. Phong. Drafting Manuscript: Tran T.M. Thu and Huynh T.N. Mi. Critical Revision of Manuscript: Doan T.K. Tien, Tran T.M. Thu, and Huynh X. Phong. Statistical Analysis: Huynh T.N. Mi, Nguyen H. Thanh, Le T.B. Son. Admin, Technical or Material Support: Tran T.M. Thu. Supervision: Doan T.K. Tien and Huynh X. Phong. Final Approval: Doan T.K. Tien and Huynh X. Phong.
6. FUNDING
The present work was financially supported by Can Tho University of Technology, Can Tho City, Vietnam and Can Tho University, Can Tho City, Vietnam.
7. CONFLICTS OF INTEREST
Doan T.K. Tien, Tran T.M. Thu, Huynh T.N. Mi, Nguyen H. Thanh, Le T.B. Son, Nguyen N. Thanh, and Huynh X. Phong declare that they have no conflicts of interest.
8. ETHICAL APPROVALS
This study does not involve experiments on animals or human subjects.
9. DATA AVAILABILITY
All the relevent data is available with the authors and can be accessed on request.
10. SUPPLEMENTARY MATERIAL:
The supplementary material can be accessed at the journal’s website Link Here: [https://jabonline.in/admin/php/uploadss/1206_pdf.pdf].
11. Publisher’s Note
All claims expressed in this article are solely those of the authors and do not necessarily represent those of the publisher, the editors and the reviewers. This journal remains neutral with regard to jurisdictional claims in published institutional affiliation.
12. USE OF ARTIFICIAL INTELLIGENCE (AI)-ASSISTED TECHNOLOGY
The authors declares that they have not used artificial intelligence (AI)-tools for writing and editing of the manuscript, and no images were manipulated using AI.
REFERENCES
1. Kumar D, Kumar S, Gupta J, Arya R, Gupta A. A review on chemical and biological properties of Cayratia trifolia Linn. (Vitaceae) Pharmacogn Rev 2011;5:184-8. [CrossRef]
2. Kumar D, Gupta J, Kumar S, Arya R, Kumar T, Gupta A. Pharmacognostic evaluation of Cayratia trifolia (Linn.) leaf. Asian Pac J Trop Biomed 2012;2:6-10. [CrossRef]
3. Doan TK, Vien HY, Huynh XP, Nguyen NT, Bui HD, Ha TT, et al. Selection of thermotolerant yeasts and application in wine production from three-leaf Cayratia (Cayratia trifolia L.) in Hau Giang. Can Tho Univ J Sci 2018;54:64-71.
4. Doan TK, Huynh TN, Tran HD, Bui HD, Nguyen NT, Ha TT, et al. Fermentation conditions, total polyphenol content, and antioxidant activity of threeleaf cayratia (Cayratia trifolia L.) wine prepared using thermotolerant yeast Saccharomyces cerevisiaeHG1.3. Asia Pac J Sci Technol 2022;27:APST-27-06-06.
5. Tien DT, Mi HT, Do ND, Toan HT, Dung NT. Total polyphenol content and antioxidant capacity of Cayratia trifolia (L) Domin berries before and after fermentation using thermotolerant yeast Saccharomyces cerevisiae HG1.3. Vietnam J Sci Technol 2018;60:60-4.
6. Tsuyoshi N, Fudou R, Yamanaka S, Kozaki M, Tamang N, Thapa S, et al. Identification of yeast strains isolated from marcha in Sikkim, a microbial starter for amylolytic fermentation. Int J Food Microbiol 2005;99:135-46. [CrossRef]
7. Naumov GI, Nguyen HV, Naumova ES, Michel A, Aigle M, Gaillardin C. Genetic identification of Saccharomyces bayanusvar. Uvarum, a cider-fermenting yeast. Int J Food Microbiol 2001;65:163-71. [CrossRef]
8. Aung W, Watanabe Y, Hashinaga F. Isolation and phylogenetic analysis of two thermotolerant, fermentative yeast strains from liquid Tapéketan (Indonesian rice wine). Food Sci Technol Res 2012;18:143-8. [CrossRef]
9. Okoduwa SI, Igiri B, Udeh CB, Edenta C, Gauje B. Tannery effluent treatment by yeast species isolates from watermelon. Toxics 2017;5:6. [CrossRef]
10. Tien DT, Phong HX, Yamada M, Toan HT, Dung NT. Characterization of newly isolated thermotolerant yeasts and evaluation of their potential for use in Cayratia trifolia wine production. Vietnam J Sci Technol Eng 2019;61:68-73. [CrossRef]
11. Pham TT, Nguyen NA, Le TD, Nguyen T, Bui HD, Huynh XP. Isolation and selection of yeast for wine fermentation from red dragon fruit (Hylocereus polyrhizus). Vietnam J Sci Technol 2019;61:54-9.
12. Mujdeci GN, Ozbas ZY. Technological and enzymatic characterization of the yeasts isolated from natural fermentation media of Gemlik olives. J Appl Microbiol 2021;131:801-18. [CrossRef]
13. Tien DT, Nhung DT, An LT, Hiep TH, Mi HT, Thanh NN, et al. Isolation and selection of yeasts from Soursop Annona muricata for wine fermentation. Vietnam J Sci Technol 2021;63:53-7.
14. Huynh XP, Huynh VK, Le TH, Tran KA, Luu MC, Nguyen NT, et al. Optimization of fermentation conditions in wine production from soursop (Annona muricata L.) using Saccharomyces cerevisiae FBY015. TNU J Sci Technol 2021;226:95-103.
15. Nguyen VT, Nguyen MT, Nguyen TM, Tran TQ, Huynh TT, Nguyen PC. Using isolated and purified yeast for pineapple (Cau Duc, Hau Giang) wine processing. Can Tho Univ J Sci 2013;27:56-63.
16. Phong HX, Loi DM, Thanh NN, Qui LP, Long BH, Thanonkeo P, et al. Selection of thermotolerant yeasts and study on fermentation conditions for pineapple wine production. Can Tho Univ J Sci 2017;51:7-15. [CrossRef]
17. Doan TK, Huynh TN, Nguyen DD, Ha TT, Ngo DT. Total polyphenol content and antioxidant capacity of Cayratia trifolia (L) Domin berries before and after fermentation using thermotolerant yeast Saccharomyces cerevisiae HG1.3. Vietnam J Sci Technol 2018;60:44-60.
18. International Organization for Standardization. Food Microbiology Including Microbiology of Animal Feeding Stuff. Available from:https://www.iso.org/ics/07.100.30/x [Last accessed on 2023 Apr 10].
19. AOAC. Official Methods 972.11-1973. Methanol in Distilled Liquors. Gas Chromatographic Method. Maryland:AOAC;2005. 1-4.
20. Vietnam National Standard 3217:79:Liquors, Sensory Evaluation-Methodlogy Test by Means of Marking, in Vietnamese. Hanoi, Viet Nam:Ministry of Science and Technology;1979.
21. Huan PT, Hien NM, Anh NH. Optimization of alcoholic fermentation of dragon fruit juice using response surface methodology. Food Res 2020;4:1529-36. [CrossRef]
22. Joshi VK, John S, Abrol GS. Effect of addition of extracts of different herbs and spices on fermentation behaviour of apple must to prepare wine with medicinal value. Nat Acad Sci Lett 2014;37:541-6. [CrossRef]
23. Pickering GJ. Low-and reduced-alcohol wine:A review. J Wine Res 2000;11:129-44. [CrossRef]
24. Hanh ND, Le Hang H. Study on use of Saccharomyces cerevisiae in cider making from Docynia indica fruit. Appl Microbiol 2016;47:21-6.
25. Narendranath NV, Power R. Relationship between pH and medium dissolved solids in terms of growth and metabolism of lactobacilli and Saccharomyces cerevisiae during ethanol production. Appl Environ Microbiol 2005;71:2239-43. [CrossRef]
26. Liu X, Jia B, Sun X, Ai J, Wang L, Wang C, et al. Effect of initial pH on growth characteristics and fermentation properties of Saccharomyces cerevisiae. J Food Sci 2015;80:M800-8. [CrossRef]
27. Attri BL. Effect of initial sugar concentration on the physico-chemical characteristics and sensory qualities of cashew apple wine. Nat Prod 2009;8:374-9.
28. Nguyen TMT, Luu MC, Nguyen NT, Bui HDL, Doan TKT, Tran TT, et al. Optimization of fermentation conditions in cider production from king orange (Citrus nobilis L. Osbeck). TNU J Sci Technol 2022;227:48-56.
29. Doan TKT, Do TTN, Dang THD, Nguyen NT, Huynh TNM, Huynh XP. Study on the appropriate conditions of the soursop (Annona muricata L.) juice fermentation using Saccharomyces cerevisiaeRV002. Vietnam J Sci Technol 2023;65:76-80. [CrossRef]