NATURAL FERMENTATIONS

There has been renewed interest among some winemakers with regard to the use of native microflora present on the fruit and in the winery to carry out alcoholic and malolactic fermentations. Stylistic distinction is the driving force that tempts winemakers to accept the risks involved in these natural fermentations. Perceived benefits include added complexity and intensity as well as a fuller, rounder palate structure. The latter may reflect the presence of small amounts of unfermented sugar, lower alcohol, and increased production of important sensory impact metabolites. 

although its presence may also enhance the quality of some wines (Mamede et al., 2005). Finally, Sommer et al. (2005) described the use of mixed active dry culture that included Saccharomyces, Kluyveromyces, and Torulaspora. 

Some non-Saccharomyces yeasts can spoil wine through synthesis of various volatile odor and flavor compounds. Yet, another concern regarding these yeasts involves nutrient depletion. Like Saccharomyces, non-Saccharomyces yeasts require various nutrients such as nitrogen, vitamins, and minerals which may be depleted before Saccharomyces initiates fermentation. This could potentially adversely affect alcoholic fermentation. 

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These defects have spurred attempts to prepare analogs. The techniques used have been (1) natural fermentation (in which... 

Yeasts tend to dominate the initial phase of the natural fermentation of cocoa pulp [1]. An isolate oiKluyveromyces marxianus (CCT 3172) was found to be the most pectinolytic of 12 yeast strains, resulting in degradation of pulp cell walls [1]. 

These defects have spurred attempts to prepare analogs. The techniques used have been (1) natural fermentation (in which the penicillin-producing fungus is allowed to grow on a variety of complex natural nutrients from which it selects acids for incorporation into the side chain), (2) biosynthetic production (in which the fermentation medium is deliberately supplemented with unnatural precursors from which the fungus selects components for the synthesis of "unnatural" penicillins), (3) semisynthetic production (in which 6-aminopenicillanic acid (2) is obtained by a process involving fermentation, and suitably activated acids are subsequently reacted chemically with 6-APA to form penicillins with new side chains) and (4) total synthesis (potentially the most powerful method for making deep-seated structural modifications but which is at present unable to compete economically with the other methods). 

Natural fermentation is a complex situation with a hodge-podge of foods and cells all busily reacting. In this introduction let us only consider the very simplest of situations ... 

The Heaven doth by the assistance of his Stars, communicate unto her heavenly, spiritual and invisible virtue, which descends first unto the Air, where it beginneth to assume a kinde of body the Air sends it into the Water or the Earth, where this celestial virtue and influence beginneth to operate more materially, and associate it self to matter, thereby to frame a body to it self by means of those various natural fermentations which are the cause of alteration in sublunary things. 

Single natural aroma compounds like natural vanillin are obtained through physical separation techniques from edible materials or through natural fermentative processes. 

We have found a high degree of correlation between induction of rapid malo-lactic fermentation and bacteria addition in starter cultures when the wines were treated as suggested above to encourage the fermentation. Peynaud and Domercq (51) obtained malo-lactic fermentation by inoculating commercial wines of a locality which had not had a natural fermentation for many years. 

Beside the natural fermentation process, dextran can be synthesised chemically via a cationic ring-opening polymerisation (ROP) of levoglucosan (1,6-anhydro-/3-D-glucose), a pyrolysis product of polyglucans (Fig. 8, [83]). 

The microorganism used was P. simplicissimum, previously isolated by Freire (5,6), using samples of babassu nuts, which were naturally fermented at a babassu oil plant. 

The final product is a naturally fermented dessert wine that has a copper to golden brown color. The mix of raisins, honey, and spices with a sweet and rich velvet-like texture is balanced by the high acidity that arises from the use of the Assyrtiko grapes. This makes the taste and bouquet of Santorini Vinsanto very particular. 

Indeed, grapes are a primary source of microorganism, and many studies have shown that natural fermentation starts with those species predominant on grapes at harvest time (Fleet et ah, 2002). These can include the apiculate yeasts (Hanseniaspora uvarum and Kloeckera apicu-lata), Metschnikozvia, Candida, Pichia, Khodotorula, and Kluyveromyces. In contrast, although it is the main wine fermentation yeast, Saccharomyces have only rarely been isolated from vineyards (Martini, 1993 Martini et ah, 1996 Pretorius, 2000 Sabate et ah, 1998), since it is closely associated with the winery environment (Ciani et ah, 2004). 

Saccharomyces species other than S. cerevisiae have often been found during spontaneous fermentation of sweet wines, such as S. bayanus and S. paradoxus during the natural fermentation of Tokaj wine (Naumov et al., 2000,2002 Sipiczki et al., 2001) and S. uvarum in the natural fermentation for the production of Recioto and Amarone wines (Dellaglio et al., 2003 Torriani et al., 1999 Tosi et al., 2009 Zapparoli et al., 2003). 

Sipiczki, M., Romano, P., Lipani, G., Miklos, I., and Antunovics, Z. (2001). Analysis of yeasts derived from natural fermentation in a Tokaj winery. Anton. Leeuwen. 79, 97-105. 

Given this situation, it would seem imperative to conduct a comprehensive study of intra-strain variability, so that winemakers could be made aware of the full rarige of flavor effects possible for a specific yeast strain. If this variability could be coupled to a wide range of fermentation conditions (that is, demonstrate, if possible, the dependence upon the extrinsic factors) then the winemakers would indeed have a powerfiil tool at their disposal. Using this knowledge the winemaker could chose the optimal strain for the conditions specific to that fermentation. Synergestic effects of multistrain (i>., natural) fermentations could then be rationally studied, as the effects of single strains would be fully characterized. 

One must also consider the financial advantage in having a process that can be easily controlled as to desugarization rate when compared with the poor control of a natural fermentation process that may have widely variable times, depending on factors beyond the control of the operator, such as ambient temperature, level of contamination, and nature of contaminant. The number of variables used in this example explains why economic justification is often not calculated on an industry-wide basis but on a plant-by-plant basis, depending on the particular local conditions that influence the components of the economic calculations. 

Through the centuries man has used pectic enzymes produced by microorganisms in natural fermentations to modify plant tissue to produce more useful products. One of the oldest fermentations is the process of retting, in which textile fibers, such as flax, hemp, and jute are loosened from their plant stems. Clostridium felsineum, one of the organisms involved in anaerobic retting, produced endopolygalacturonase and endopolygalacturonate lyase but not pectinesterase 178, 179). 

Ivermectins B1 are derived from the avermectines Bl, the natural fermentation products of Streptomyces avermitilis. The avermectins Bl have double bonds between carbon atoms at 22 and 23, whereas the ivermectins Bl have single bonds in these positions (Fig. 2a). They have an intermediate polarity. The ivermectins Bl are a mixture of two major homologs, ivermectins Bla (>80%) and ivermectins Bib (<20%), but a crude ivermectin complex also contains various minor components. Ivermectins Bl are broad-spectrum antiparasitic agents used against Onchocerca volvulus in human medicine and for food production animals such as cattle, swine, and horses. 

Ivermectins B1 are broad-spectrum antiparasitic agents widely used for food-producing animals such as cattle, swine, and horse.They are derived from avermec-tins Bl, the natural fermentation products of Strepto-myces avermitilis. 

Alcohol prohibition was enacted several years later when in 1920, Congress passed the Eighteenth Amendment to the Constitution. The legislation was a victory for the forces that viewed alcohol as evil and destructive, notably the Anti-Saloon League and the Women s Christian Temperance Union. And the amendment was not vague about its intent It prohibited the production, sale, transportation, and importing of alcohol in any part of the United States. The only exception was that alcoholic beverages kept in the home, such as naturally fermented hard cider, could be consumed but not offered for sale (Lender Martin, 1982). 

With most biotechnologically produced flavour extracts the taste quality of natural fermentation processes can be reached and even surpassed. Normally the taste intensity is significantly higher compared to the usual fermentation process in the raw food material. Even completely new taste types may be accessible biotechnologically. The time necessary for the development of the desired taste in most cases may be signifi-... 

Fermentation plays an important role in the development of specific, characteristic flavourings. Natural fermentation is used since thousands of years to get wine, beer or cheese. Modem biotechnological processes have been developed to produce flavourings and flavouring building blocks based on natural processes. There are many important fermented products on the markets, produced by traditional and industrial processes ... 

A wider range of product variety and alcohol content is possible with wine than with beer. The natural wines, also called table or dinner wines, are those in which the alcohol content is derived entirely by natural fermentation. This limits the alcohol content to about 7-14%, by volume. The upper end of this concentration range is only attainable by using special varieties of wine yeasts. However, all have a higher alcohol content than even the malt liquor types of beer. 

As a result of the build-up of antibiotic resistance, the demand for derivatives from penicillins and cephalosporins rather than for the natural fermentation products has increased. One of the problems in the manufacture of semi-synthetic penicillins and cephalosporins is that fhese are vulnerable compounds and chemical modification is elaborate and difficult. Modification of fhe initial fermentation products penicillin G/V and cephalosporin G by the use of enzymes has provided economically feasible routes to semi-synthetic penicillins and cephalosporins [31]. 

Mortimer, R.K., Romano, P., Suzzi, G., and Polsinclli, M. 1994. Genome renewal A new phenomenon revealed from a genetic study of 43 strains of Saccharomyces cerevisiae derived from natural fermentation of grape musts. Yeast 10,1543-1552. 

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