Initial Fermentable Sugar Levels

Sucrose, in the case of grapes, is present at low concentrations, accounting for 0.2-1.0 g/100 g (Hawker et al., 1976). Unless used in chaptaliza-tion, the dissaccharide is of little importance during fermentation. Saccha-romyces produces an extracellular invertase which catalyzes its immediate hydrolysis thus, the sugar is fully fermentable. 

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Wild apricot (Prunus armenica L.) grows naturally in hilly areas of northern India. It is highly acidic, fibrous, and low in TSS, and, thus, not utilized commercially. Preparation and evaluation of a vermouth from its fruit was undertaken (Abrol, 2009). Vermouths at different sugar (8,10, and 12 °Brix), alcohol (15%, 17%, and 19%), and spices levels (2.5% and 5%) were prepared. Those used in extract preparation are shown in Plate 8.1. The base wine was prepared from crushed fruit, adjusted to 24 °Brix, and diluted in a 1 2 ratio with water. To this mixture was added 200 ppm sulfur dioxide, 0.1% diammonium hydrogen phosphate (DAHP), and 0.5% pectinase enzyme. A 24-h active yeast culture initiated fermentation. The procedure is illustrated in Fig. 8.4. A maturation period of 6 months improved the quality of the vermouth. 

As discussed in Chapter 4, the intrinsic properties of juice, fermentation, and wine play important antimicrobial roles. These include, initially, sugar levels that are well above optimal for most microorganisms. Coupled with unfavorable osmotic conditions, the grape s inherent acidity and low pH also serves to limit microbial diversity and numbers. 

Acidity can be corrected (Section 11.4) during the initial transfer into vat or at a later time. If sugar levels need to be increased (chaptaUzation, Section 11.5.2), this is best done when the mnst is warm at the beginning of fermentation. The sngar dissolves more easily and the subsequent aeration stimulates fermentation, while relatively low sugar levels promote multiplication of the yeast cells during the growth phase. 

Investigators in the field were initially focused on finding microbes that could secrete high levels of saccharolytic enzymes that could be recovered and used to generate soluble sugars for fermentation by noncellulolytic microbes such as yeast (see discussion in [1]). 

These initial investigations permit bacterial identification at the genus level Lactobacillus by morphology, and Pediococcus and Leuconostoc by morphology and determination of their homofermentative or heterofermentative character. Classification at the species level makes use of the analysis of the fermentation profiles of a large number of sugars. 

Initially sugars were used extensively for the production of lA. However, using sugars as a carbon source is very expensive for industrial levels of production, which demand economically feasible substrates, such as starch, molasses, wood, or corn syrup hydrolyzates and other combinations (Klement et al., 2012 Klement and Biichs, 2013 Sieker et al., 2012). Nevertheless, beet or sugarcane molasses are the most commonly used carbon sources (Nubel and Ratajak, 1964), which are pretreated by ion exchange or ferrocyanide and subsequently used for fermentation (Bath and Schweiger, 1963). Apart from these, other varieties of... 

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