1 Introduction

It has been recognized internationally that wine is the alcoholic beverage resulting exclusively from the fermentation of grape or grape must. This is stated clearly in the definition of wine in the International Code of Oenological Practices issued by International Organization of Vine and Wine with its 47 member states. Various wine producing countries have also implemented regulations controlling the use of grape varieties and the amounts of harvest that can be used to produce particular wines. Thus, it is apparent that alcoholic beverages fermented from other fruits are not recognized as wine by international convention. By trials and errors since antiquity, grape was found most suitable and is solely utilized as raw material for winemaking. All modern winemakers still place great care in the vineyards to obtain perfectly sound grapes for winemaking and they understand that winery operations can only enhance the already good quality grapes (Rankine 2004). These facts indicate that fermented beverages of grape origin only are accepted as wine. However, other fruits and sugary substrates have been fermented to obtain various alcoholic beverages but they were assigned specific names corresponding to the type of raw materials employed. These include cider from apple, mead from honey and sake from rice.

Due to the lack of international agreement on production practices for fruit wines, alcoholic beverages from fruits other than grape and apple are called fruit wine with a particular fruit name, for example, pineapple wine, peach wine and strawberry wine. These names have confused consumers with wine (from grape) causing them to expect similar quality and flavor as that of table wine. But most fruits have different compositions and microflora from grape and the resulting beverages are usually significantly different in quality.

In order to produce high quality fruit wines, these differences must be taken into account and utilized to optimize the style of the beverage that reflects the nature of the fruit as well as the production process to obtain a suitable product which could be much different from conventional wines, with unique characteristics and benefits. In this respect, the roles of yeasts during fermentation are one of the most important factors to be considered in the development of alcoholic beverages from fruits.

In wine made from grape, the roles of yeasts that contribute to overall wine quality are well documented and already discussed in previous chapters of this book. These include the following:

  1. 1.

    Yeasts metabolize sugars and nitrogen compounds into alcohols and other flavor compounds, impacting wine quality;

  2. 2.

    Ethanol produced by yeasts not only affects organoleptic property but also acts as solvent extracting color and flavor, such as tannins from grape into wine;

  3. 3.

    Enzymatic activities resulting from yeast growth can transform flavor precursors present in grape must into flavor active compounds, such as glycosidase enzymes;

  4. 4.

    Yeast fermentation increases the concentrations of some organic acids but decreases some acids and some phenolic compounds are transformed into volatile compounds;

  5. 5.

    In cases of lees contact, dead yeast cells will decompose by autolytic enzymes and will impart specific characteristics known to be associated with autolysis;

  6. 6.

    Yeast cell walls can absorb certain wine constituents, resulting in decreasing amounts of these compounds.

These yeast contributions to wine quality in different fruit systems could differ from those occurring in grape and, therefore, must be thoroughly investigated before optimized production process can be designed for a certain fruit.

2 Opportunities for Fruit Wines

Throughout the world, many different kinds of fruits are cultivated and commercialized. Some fruits are only available during specific seasons and can attain high value when retailed as fresh products such as durian, lychee and mangosteen but others are produced in large quantities during longer period of time, causing their values to decline significantly. Even high-valued fruits may undergo similar problem with over production in certain years due to favorable climatic conditions. Furthermore, cultivation areas for popular fruits are expanding, replacing original crops, causing over supply. In order to gain some revenues from overproduced fruits, they are normally processed into preserves, jams, canned fruits and other products but these are too common for consumers and do not increase much higher revenue for producers. An interesting alternative of producing value added products from over-supplied fruits is fruit-winemaking. They can be marketed at higher values and attain much higher profits due to the nature of alcoholic beverages which tends to be marketed as high value products indicating social status.

A new trend in beverage market is the consumption of low alcohol and this trend has been determined by many factors, such as health awareness of consumers and the enforcement of restrictions on alcohol consumption by excise taxes and alcohol control laws in many countries. These restrictions aim to reduce alcohol related illnesses and road accidents caused by irresponsible drivers under the influence of alcohol intoxication. Fruit juices usually contain lower amounts of fermentable sugars than wine grapes and therefore could yield new products with low concentrations of ethanol. International Code of Oenological Practices indicates that wine must contain over 8.5% alcohol but fruit wine products can have lower alcohol content without violating any international standard.

Modern consumers are always searching for new products. Alcoholic beverages from different kinds of fruits with their unique flavor could cater for this market. Alcoholic beverages from exotic fruits can deliver their special characteristics to consumers in distance market without the need to transport fresh products over long distance in refrigerated containers. Even commonly known product in one country could be a new product in another. For example, sake or rice wine from Japan has been popular in the United States where as many brands of American cider are distributed widely in Japan. Thus, wine made from tropical fruits could be appreciated by consumers in temperate zones and vice versa.

All over the world, health and functional foods have gained increasing interests by producers and consumers alike. Fruit wines offer various health benefits such as antioxidant activity from phenolic compounds found in many fruits. Total phenols and antioxidant activities had been investigated by Kalkan Yildirim (2006) in different fruit wines made from black mulberry, blackberry, quince, apple, apricot, melon, red raspberry, bilberry, sour cherry and strawberry. The highest value of antioxidant activities and total phenolic contents were determined in bilberry, blackberry and black mulberry wines (61.80%, 1161 mg/l gallic acid equivalents; 60.00%, 1232 mg/l gallic acid equivalents; 58.10%, 1081 mg/l gallic acid equivalents), respectively. These results showed a potential as natural antioxidants of bilberry, blackberry and black mulberry wines.

Ortiz et al. (2013) determined antioxidant activity of wines made in Ecuador from Andean blackberries (Rubus glaucus Benth.) and bluberries (Vaccinium floribundum Kunth.) and Golden Reinette apples and found that Andean blackberries had the highest total phenolic content (1265 ± 91 mg/L) and antioxidant activity (12 ± 1 mM). They concluded that these berries are suitable raw materials to produce wines with an in vitro antioxidant capacity that is comparable to red grape wines.

Commercially available fruit wines from blackberry, cherry, raspberry, blackcurrant, strawberry and apple produced in Croatia were analyzed by Ljevar et al. (2016). The results showed that blackberry, cherry and blackcurrant wines contained the highest amount of total phenolic compounds, while cherry and blackcurrant wines also contained the highest amount of total anthocyanins. Blackberry, followed by cherry, raspberry and blackcurrant wines also had a significantly higher antioxidant capacity than strawberry and apple wines. Fruit wines inhibited the growth of human cancer cells in vitro in a dose-dependent manner with differing susceptibility among tested cancer cells.

Phenolic contents and antioxidant activities found in fruit wines might not correlate with actual health benefits, so many researchers had investigated the effects of fruit wines as antioxidant agents in vivo. Srikanta et al. (2016) found that feeding mulberry and jamun wines to streptozotocin-induced diabetic rats increased antioxidant enzymes and hepatic glutathione contents but decreased non-esterified fatty acids and lipid peroxidation. These findings suggest that fruit wines can be beneficial as antioxidants. Escudero-López et al. (2018) evaluated the potential effect on cardiovascular risk factors of the regular consumption by healthy humans of a beverage obtained by alcoholic fermentation and pasteurization of orange juice. It was found that fermented orange beverage intake significantly increased oxygen radical absorbance capacity (43.9%) and reduced uric acid (−8.9%), catalase (CAT) (−23.2%), thiobarbituric acid reactive substances (TBARS) (−30.2%) and C-reactive protein (−2.1%). They concluded that regular consumption of orange could result in protecting the cardiovascular system in healthy humans and be considered a novel functional beverage.

Fruits are important sources of vitamins. Alcoholic fermentation affects vitamin contents in grape wines, resulting in decreased vitamin contents (Rankine 2004). However, in fruit wines the effect varies, depending on the fruit matrixes. Escudero-López et al. (2018) found that ascorbic acid contents in fermented orange beverage did not undergo a significant change. In another study (Cerrillo et al. 2014), significant increases in carotenoid content and provitamin A value of fermented orange juice were observed from day 0 (5.37 mg/L and 75.32 RAEs/L, respectively) until day 15 (6.65 mg/L and 90.57 RAEs/L, respectively). The authors suggested that the increases were probably due to a better extractability of the carotenoids from the food matrix as a result of fermentation.

3 Challenges in Fruit Wine Fermentation

In order to fully utilize the potential benefits of fruit wines, information on various aspects of production process and the nature of the fruits including the following topics must be investigated.

  1. 1.

    Fruit juice extraction and process to obtain suitable musts for fermentation

  2. 2.

    Ecology of yeasts and factors affecting their presence in fruit juices and wines

  3. 3.

    Microbiology of fermentation, starter culture and fermentation conditions tailored for particular fermentation

  4. 4.

    Contributions of fermentation to beverage quality

Figure 15.1 illustrates various aspects and approaches in the development of fruit wines that need to be chosen according to different fruits and style of beverage desired. It can be seen that at each stage of production, a set of alternatives is available. These factors influence the outcome of the finished wines as in conventional winemaking and have to be taken into account with detailed scientific studies.

Fig. 15.1
figure 1

Different approaches in the development of fruit wines

Full size image

4 Fruit Juice Pre-Treatments

Unlike grape, many fruits contain skins that must be peeled off and the pulps cut in to small pieces for subsequent juice extraction. During the peeling and cutting processes, indigenous yeast flora on the surface of the peels could be transferred into the extracted juice. Fruits without skin also have yeast microflora on the surface that can carry out alcoholic fermentation. Furthermore, depending on the equipment and method being employed, yeasts colonizing in the environment of the processing plant can also contaminate into the musts and influence the overall fermentation.

Some fruits, especially those with low water contents, require further extraction processes in order to obtain sufficient amount of juice to be fermented. Heat treatment, such as pasteurization, is used to reduce microbial contamination and facilitate juice extraction of some fruits. However, heat can change the composition of the juice and affect nutrient availability for yeast fermentation. Ascorbic acid, total flavanones, total carotenoids and provitamin A values were found to decrease after pasteurization (Escudero-López et al. 2016). On the other hand, Cerrillo et al. (2015) found that, although pasteurization of orange juice produced partial amino acid degradation, the total amino acid content was higher in the final product than in the original juice. These changes could affect the growth of yeasts, resulting in modified flavor of finished beverages.

Higher acidity of the musts can affect organoleptic characteristics of fruit wines. This problem was rectified by dilution of fruit juices to obtain acceptable ranges of acidity (Akubor 1996). However, this practice also reduces concentrations of fruit sugars as well as nitrogen compounds necessary for yeast growth. Most fruits, even without acid dilution, contain less sugars than grape and therefore chaptalization or the additions of sucrose into the musts can be employed in order to increase alcohol contents of the finished wines (Akubor 1996; Jitjaroen 2007; Duarte et al. 2010; Won et al. 2015; Satora et al. 2018). Nutrient addition commonly practiced in the wine industry is also necessary in fruit juices pre-treatment, especially those with acid dilution. Jitjaroen (2007) studied the effects of nutrient supplements in banana, santol and ma-mao juices. It was found that banana juice supplemented with 1000 mg/L diammonium phosphate (DAP) and santol juice supplemented with 1000 mg/L DAP and 0.6 mg/L thiamine showed less sulfur binding capacities, resulting in perceptible dryness.

These pre-treatment practices affect yeast growth and their metabolic activities, resulting in the final quality of the finished wines.

5 Ecology of Yeasts in Fruit Juices and Wines

It is well documented that indigenous yeasts belonging to the genera Candida, Kloeckera/Hanseniaspora, Pichia, Metschnikowia, Kluyveromyces and other non-Saccharomyces grow during the early stages of alcoholic fermentation of grape juice into wine, although strains of Saccharomyces cerevisiae predominate mid to later stages of fermentation (Fleet and Heard 1993; Fleet 2003). Indigenous yeasts represent the microflora of the grapes and S. cerevisiae is present in low numbers on grapes and can also originate from winery equipment. Similar occurrences were observed in other fermentation systems such as those in palm wines (Stringini et al. 2009; Ouoba et al. 2012) and traditional rice wine in South East Asia where Saccharomycopsis fibuligera occurred during saccharification of rice (Thanh et al. 2016; Farh et al. 2017). Therefore, it can be expected that in many fruit wine fermentation systems, succession of yeast domination phases could also occur. Indigenous yeasts from the fruits would grow during the early stages of fermentation and then die out, leaving S. cerevisiae as the main fermenting yeast to complete the alcoholic fermentation.

Among the fruit wines, cider is one of the oldest known beverages and is produced in more than 25 countries around the world and the highest production and consumption is mainly in European countries (about 70–80%). It must be underlined that the appreciation of this fermented beverage is linked to the recognition of its “territoriality”. Indigenous yeasts can actively contribute to the expression of cider typicality and significantly influence the sensory profile of cider.

Thus, Morrissey et al. (2004) examined the role of the indigenous yeast flora in traditional Irish cider fermentations, finding Hanseniaspora uvarum to predominate in the initial phase of fermentation. Thereafter Saccharomyces cerevisiae dominated in the alcoholic fermentation phase. Coton et al. (2016) isolated from unpasteurized ciders and different cider musts 15 yeast species, the dominant being Saccharomyces bayanus (about 35%), followed by S. cerevisiae and non-Saccharomyces yeasts, such as Lachancea cidri , Dekkera anomala and Hanseniaspora valbyensis .

The roles of yeasts in apple or cider fermentation have been reviewed by Cousin et al. (2017).

Fruit juices under sterile condition without contact with winery equipment such as the juice press, fermentation tanks and pumps do not yield adequate alcohol concentrations for stable beverage products without pasteurization. This is due to the lack of fermentative Saccharomyces yeasts from winery equipment. Freshly pressed pineapple juices obtained from Thailand, Australia and Angola were allowed to ferment spontaneously by native microflora (Chanprasartsuk et al. 2010; Dellacassa et al. 2017). The yeasts Hanseniaspora uvarum and Pichia guilliermondii predominated all fermentations yielding low alcohol contents (2–4% by volume). S. cerevisiae was not found in any of the fermentations. When pineapple juice was inoculated with selected strains of S. cerevisiae, the fermentable sugars were completely consumed from initial value of 24 °Brix (Baidya et al. 2016).

6 Yeast Starter Cultures and Their Contributions to Fruit Wine Quality

Since relying on naturally occurring Saccharomyces yeasts from winery environment can result in uncontrollable fermentations with inconsistent wine qualities, inoculation with desired strains of S. cerevisiae has become standard practice in most wineries (Reed and Nagodawithana 1988). However, Fleet and Heard (1993) had proposed that not only the inoculated S. cerevisiae that determine the characteristics of the resulting wines but also indigenous yeasts that grow during the early stages of fermentation. Subsequent studies have confirmed the contributions of indigenous yeasts to overall wine flavor profiles and the use of alternative yeasts as co-starter with S. cerevisiae or as single cultures in grape wine fermentations have been reported and these have been reviewed by Fleet (2008).

For fruit wine fermentations, many studies regarding yeast fermentation have been carried out for different fruit juices and these have been reviewed by Prakitchaiwattana and Tananuwong (2011) and Chanprasartsuk and Prakitchaiwattana (2015). Species of Saccharomyces have been examined for their potential as starter cultures. Sixteen different strains of Saccharomyces cerevisiae and Saccharomyces bayanus were evaluated in the production of raspberry fruit wine (Duarte et al. 2010). Various kinetic parameters were determined and compared. One strain of S. cerevisiae was recommended for the fermentation of raspberry juice which produced a fruit wine with low concentrations of acids and high concentrations of acetates, higher alcohols and ethyl esters.

Three commercial S. cerevisiae yeast strains were evaluated for the production of pomegranate wine (Berenguer et al. 2016). The same fermentation patterns were observed for pH, titratable acidity, density, sugar consumption, and ethanol and glycerol production. A high ethanol concentration (10.91 ± 0.27% v/v) in combination with 1.49 g/L glycerol was achieved. Citric acid concentration increased rapidly at 31.7%, malic acid disappeared as a result of malolactic fermentation and the lactic acid levels reached values between 0.40 and 0.96 g/L. The analysis of total anthocyanin content highlighted a lower degradation of monomeric anthocyanins during winemaking with Viniferm PDM yeast. The resulting wine retained 34.5% of total anthocyanin content of pomegranate juice blend.

Saccharomyces uvarum strains were isolated from traditional fermentations of apple chicha in Patagonia, a region covering Argentina and Chile (Rodríguez et al. 2017). This research group also studied the physiological characteristics of S. uvarum and Saccharomyces eubayanus strains recovered from natural habitats and traditional fermentations. The yeast S. uvarum produced high glycerol levels, low acetic acid and increased production of the higher alcohol 2-phenylethanol and 2-phenylethyl acetate. Similar properties were observed for S. eubayanus. The combination of these strains can be used as a starter culture in cidermaking (González et al. 2017).

Non-Saccharomyces yeast species possess various characteristics which could be beneficial to fruit wine fermentations and these yeasts were investigated for their potential as single, sequential or co-starter cultures with S. cerevisiae. Volatile compounds formed during fermentation of papaya juice using a mixed culture of Saccharomyces cerevisiae and Williopsis saturnus were analyzed by Lee et al. (2010). Different volatile compounds were produced during fermentation including fatty acids, alcohols, aldehydes and esters but some volatile compounds, including those initially present in the juice, were utilized. The mixed culture fermentation by S. cerevisiae and W. saturnus benefited from the presence of both yeasts, with more esters being produced than the S. cerevisiae monoculture fermentation and more alcohols formed than the product fermented with W. saturnus alone. It was suggested that papaya juice fermentation with a mixed culture of S. cerevisiae and W. saturnus may be able to result in the formation of more complex aroma compounds and higher ethanol level than those using single yeasts. They also found that the yeast ratio of W. saturnus and S. cerevisiae in sequential fermentation of papaya wine was an important factor affecting fermentation performances (Lee et al. 2013).

Rodríguez-Lerma et al. (2011) studied the microbial ecology of spontaneous fermentation to select a starter culture for prickly pear wine production. Results showed that a mixed starter inoculum containing Pichia fermentans and S. cerevisiae yielded a fermented product that contained 8.37% alcohol (v/v). Analysis of volatile compounds revealed the presence of 9 major alcohols and esters (isobutanol, isopentanol, ethyl acetate, isoamyl acetate, ethyl octanoate, ethyl decanoate, ethyl 9-decanoate, β-phenylethyl acetate, and phenylethyl alcohol) that contributed to fruity, aromatic notes essential for desirable wine quality. It was concluded that combinations of Saccharomyces and non-Saccharomyces strains could be used to obtain high-quality fermented beverages from prickly pear juice.

A mixed culture of Saccharomyces cerevisiae and Williopsis saturnus var. mrakii was used to ferment three varieties of mango juices (Li et al. 2012). Both yeasts grew well and fructose, glucose and sucrose were consumed to trace levels in all juices. But since only one ratio of yeast mixture was used, comparison between volatile constituents of mango wines could be distinguished between different mango varieties.

Strains of S. cerevisiae, Pichia kudriavzevii , Pichia fabianii and Saccharomycopsis fibuligera were isolated from masau fruits and their traditionally fermented fruit pulp in Zimbabwe and tested for production of flavor compounds during fermentation of masau wines (Nyanga et al. 2013). It was found that S. cerevisiae strains produced higher amounts of ethanol and flavor compounds as compared to the other species, especially fatty acid ethyl esters that provide the major aroma impact of freshly fermented wines.

Sun et al. 2014 examined the effect of mixed fermentation of non-Saccharomyces (Torulaspora delbrueckii and Metschnikowia pulcherrima) and Saccharomyces cerevisiae on the production of cherry wines. Mixed culture of S. cerevisiae/M. pulcherrima was found to significantly enhance the production of higher alcohols, esters, acids and terpenes; while the characteristic of S. cerevisiae/T. delbrueckii pair was an increase in fruity esters, higher alcohols and decrease in acid production. The differences in the aromatic composition of the cherry wines were confirmed by the sensory evaluation.

Satora et al. (2014) investigated the influence of Wickerhamomyces anomalus killer yeast on the fermentation and chemical composition of apple wines. The yeast was inoculated together with S. cerevisiae strain as a mixed culture. It was found that the addition of W. anomalus killer strains to the unpasteurized must significantly decreased volatile acidity, while increased the amount of higher alcohols and titratable acidity. It was concluded that the use of W. anomalus strains together with S. cerevisiae as a mixed culture positively influenced the chemical composition and sensory characteristics of apple wines.

Ye et al. (2014) studied the effects of sequential mixed cultures of Wickerhamomyces anomalus and S. cerevisiae on apple cider fermentation. The results showed that growth of W. anomalus and S. cerevisiae was affected by each other during co-fermentation process. All the mixed cultures produced statistically the same level of ethanol as S. cerevisiae monoculture. The mixed fermentation produced more variability and higher amounts of acetate esters, ethyl esters, higher alcohols, aldehydes, and ketones. Sensory evaluation showed that ciders obtained from co-fermentation with W. anomalus obtained higher scores than ciders fermented by pure culture of S. cerevisiae.

Chen et al. (2015) evaluated the performance of Torulaspora delbrueckii , Williopsis saturnus , and Kluyveromyces lactis in lychee wine fermentation. It was found that T. delbrueckii had the fastest growth rate and high sugar consumption, producing the highest level of ethanol (7.6% v/v), while K. lactis and W. saturnus produced lower amounts (3.4% v/v and 0.8% v/v, respectively). Furthermore, K. lactis and W. saturnus over-produced ethyl acetate which was considered detrimental to wine quality. The yeast T. delbrueckii produced high levels of isoamyl alcohol, 2-phenylethyl alcohol, ethyl octanoate, and ethyl decanoate and retained high aroma-character compounds. It was concluded that this yeast could be a promising non-Saccharomyces yeast for lychee wine fermentation.

Minnaar et al. (2017) studied the effect of using Schizosaccharomyces pombe and Saccharomyces cerevisiae yeasts in sequential fermentations on phenolic acids of fermented Kei-apple (Dovyalis caffra L.) juice. Kei-apple wines obtained by sequential cultures of S. pombe and S. cerevisiae showed substantially lower concentrations of L-malic acid and had lower phenolic acid concentrations than Kei-apple wines produced with S. cerevisiae only. However, wine judges described the Kei-apple wines produced with the two yeast combination as having noticeable off-odors, while those produced with S. cerevisiae were described as fresh and fruity.

Influence of selected Saccharomyces and Schizosaccharomyces strains and their mixed cultures on chemical composition of apple wines was investigated by Satora et al. (2018). It was found that S. bayanus strain increased the level of malic acid and carbonyl compounds in apple wines, while Sch. pombe highly deacidified it and produced the most amounts of glycerol, esters, and acetic acid. The wines obtained with these species gained the best and the worse notes, respectively, during sensory analysis. Mixed yeast cultures produce higher amounts of ethanol, methanol, and volatile esters compared to pure cultures.

7 Factors Affecting the Growth and Metabolites Production of Yeasts in Fruit Wines

Various factors influence yeast growth and their metabolic activities, resulting in differing flavor profiles of finished products, depending on the compositions of fruit juices and other environmental factors. These factors such as sugar concentrations, nitrogen and other nutrients availability, pH, temperature and the addition of sulfur dioxide are important parameters in controlling fermentation of grape wines and have been well documented (Fleet and Heard 1993). In fruit juice fermentations, these parameters are also important in determining the final quality of fruit wines. Most studies concerning fruit wines mainly focused on yeast fermentation. There were fewer studies carried out on different fermentation conditions as affected by environmental factors.

Temperature of fermentation is one of the most important factors determining the production of volatile compounds by yeasts but it is also the most difficult parameter to control in fruit wine fermentations, especially in the tropical regions. Many studies on fruit wine fermentations were carried out at higher temperatures than those used for grape wine (Jitjaroen 2007; Peng et al. 2015; Lu et al. 2017a, b). This is probably due practical reasons since cooling requirements in these climates involve high running costs. Reddy and Reddy (2011) examined the effect of fermentation conditions on yeast growth and volatile composition of mango wine. Temperature had important effect on yeast growth and on the levels of volatile compounds. It was observed that the final concentrations of ethyl acetate and some of the higher alcohols decreased when fermentation temperature increased to 25 °C. Sulfur dioxide stimulated the yeast growth up to certain levels and in excess it inhibited the yeast metabolism. Ethanol concentration slightly increased with the addition of 100 ppm SO2 and decreased with increase in concentration of SO2. Aeration by shaking increased the viable cell count but decreased the ethanol productivity.

Temperature effect during fermentation of apple wine on the key aroma compounds and sensory properties were investigated by Peng et al. (2015). The concentration of nine key aroma compounds (ethyl acetate, isobutyl acetate, isopentyl acetate, ethyl caprylate, ethyl 4-hydroxybutanoate, isobutyl alcohol, isopentyl alcohol, 3-methylthio-1-propanol, and benzeneethanol) in apple wine significantly increased with the increase of fermentation temperature from 17 to 20 °C, and then eight out of the nine key aroma compounds, with an exception of ethyl 4-hydroxybutanoate, decreased when the temperature increased from 20 to 26 °C. The results showed that temperature control is of great importance in fruit winemaking.

Lu et al. (2017b) investigated the effects of temperature (20 and 30 °C) and pH (pH 3.1, 3.9) on the changes in chemical constituents of durian wine fermented with S. cerevisiae. Temperature significantly affected growth of S. cerevisiae EC-1118 regardless of pH with a higher temperature leading to a faster cell death. The pH had a more significant effect on ethanol production than temperature. However, relatively higher levels of isobutyl alcohol and isoamyl alcohol were produced at pH 3.1 than at pH 3.9 regardless of temperature. In contrast, production of esters was more affected by temperature than pH, where levels of ethyl esters and acetate esters were significantly higher at 20 °C than at 30 °C. Higher temperature improved the reduction of volatile sulfur compounds. The authors concluded that temperature control would be a more effective tool than pH in modulating the resulting aroma compound profile of durian wine.

Sulfur dioxide is widely used in the wine industry to control oxidation and for microbial stability. It is also used in industrial fermentation of other fruits, such as apple juice into alcoholic cider. Herrero et al. (2003) studied the effect of sulfur dioxide on the production of flavor volatiles during industrial cider fermentation. Addition of 100 mg/L SO2, which is the level frequently used in industrial cidermaking, induced higher acetaldehyde production by yeast than that obtained without SO2. These amounts of acetaldehyde could prevent the occurrence of simultaneous alcoholic and malolactic fermentation, which is desirable in reducing malic acid in apple cider.

Lu et al. (2017a) investigated the effect of initial sugar concentrations (17, 23 and 30 °Brix) on mango wine composition fermented by Saccharomyces cerevisiae MERIT.ferm. It was found that growth rate and maximum cell population were inversely correlated with initial sugar levels, with the fastest growth rate and largest cell population in the low sugar fermentation. However, the cell population in the low and medium sugar fermentation declined significantly relative to the high sugar fermentation in which cell populations remained stable upon reaching the stationary phase. Glycerol production increased with increasing sugar content in low, medium and high sugar fermentation. In addition, high sugar fermentation had a negative impact on volatile production with significantly lower amounts of acetate esters but more acetic acid compared to the low and medium sugar fermentations. The authors concluded that mango wines fermented with different levels of sugars would have different flavor and aromas.

8 Conclusions

Fruit juices present opportunities for the development of new alcoholic beverages with their original color, flavor, antioxidants and other bioactive compounds with potential health benefits. The development of alcoholic beverages from fruits must take into account various aspects and approaches available at each stage of the production process. Pre-treatment of the juices can provide suitable medium for yeast fermentation but some practices could be detrimental to wine quality due to their effect on chemical compositions of the mash. Indigenous yeasts already present in the pressed musts could survive during fruit-winemaking process and influence chemical and sensorial properties of the resulting wine. These yeasts have different fermentation profiles than Saccharomyces cerevisiae wine strains and their roles in spontaneous or inoculated fermentations must be elaborated in each particular juice. Factors such as temperature, pH, sugar concentrations, and the presence of sulphur dioxide affect growth and fermentation activities of yeasts at varying degrees and a suitable combination of these factors must be obtained by systematic investigations. Thorough understandings is necessary of metabolic behavior and characteristics of Saccharomyces and non-Saccharomyces yeasts that can offer unique characteristics and can be employed to obtain desirable styles of fruit wines.

9 Dedication

This chapter is based on a lecture given by Prof. Graham H. Fleet during the Thai Fruit Wine Seminar held in conjunction with the Third International Symposium on Tropical Wine held during 12–18 November 2011 in Chiang Mai, Thailand. The author wishes to dedicate this chapter to his memory.