Introduction

Campbell-Platt defined fermented foods as 'those foods that have been subjected to the action of micro organisms or enzymes so that desirable biochemical changes cause significant modification in the food'. The processes may make the foods more nutritious or digestible, or may make them safer or tastier, or some or all of these.

Most fermentation processes are extremely old. Of course, nobody had any idea of what was actually happening when they were preparing these products - it was artisan stuff. However, experience, and trial and error, showed which were the best techniques to be handed on to the next generation, so as to achieve the best end results. Even today, some producers of fermented products - even in the most sophisticated of areas such as beer brewing - rely very much on 'art' and received wisdom.

Several of the products described in this book originate from the Middle East (the Fertile Crescent - nowadays known as Iraq) some 10 000-15 000 years ago. As a technique, fermentation was developed as a low energy way in which to preserve foods, featuring alongside drying and salting in days before the advent of refrigeration, freezing and canning. Perhaps the most widespread examples have been the use of lactic acid bacteria to lower the pH and the employment of yeast to effect alcoholic fermentations. Preservation occurs by the conversion of carbohydrates and related components to end products such as acids, alcohols and carbon dioxide. There is both the removal of a prime food source for spoilage organisms and also the development of conditions that are not conducive to spoiler growth, for example, low pH, high alcohol and anaerobiosis. The food retains ample nutritional value, as degradation is incomplete. Indeed changes occurring during the processes may actually increase the nutritional value of the raw materials, for example, the accumulation of vitamins and antioxidants or the conversion of relatively indigestible polymers to more assimilable degradation products.

The crafts were handed on within the home and within feudal estates or monasteries. For the most part batch sizes were relatively small, the production being for local or in-home consumption. However, the Industrial Revolution of the late eighteenth Century led to the concentration of people in towns and cities. The working classes now devoted their labours to work in increasingly heavy industry rather than domestic food production. As a consequence, the fermentation-based industries were focused in fewer larger companies in each sector. Nowadays there continues to be an interest in commercial products produced on the very small scale, with some convinced that such products are superior to those generated by mass production, for example, boutique beers from the brewpub and breads baked in the street corner bakery. More often than not, for beer if not necessarily for bread, this owes more to hype and passion rather than true superiority. Often the converse is true, but it is nonetheless a charming area.

Advances in the understanding of microbiology and of the composition of foods and their raw materials (e.g. cereals, milk), as well as the development of tools such as artificial refrigeration and the steam engine, allowed more consistent processing, while simultaneously vastly expanding the hinterland for each production facility. The advances in microbiology spawned starter cultures, such that the fermentation was able to pursue a predictable course and no longer one at the whim or fancy of indigenous and adventitious microflora.

Thus, do we arrive at the modern day food fermentation processes. Some of them are still quaint - for instance, the operations surrounding cocoa fermentation. But in some cases, notably brewing, the technology in larger companies is as sophisticated and highly controlled as in any industry. Indeed, latter day fermentation processes such as those devoted to the production of pharmaceuticals were very much informed by the techniques established in brewing.

Fermentation in the strictest sense of the word is anaerobic, but most people extend the use of the term to embrace aerobic processes and indeed related non-microbial processes, such as those effected by isolated enzymes.

In this book, we will address a diversity of foodstuffs that are produced according to the broadest definitions of fermentation. I start in Chapter 1 by considering the underpinning science and technology that is common to all of the processes. Then, in Chapter 2, we give particularly detailed attention to the brewing of beer. The reader will forgive the author any perceived prejudice in this. The main reason is that by consideration of this product (from a fermentation industry that is arguably the most sophisticated and advanced of all of the ones considered in this volume), we address a range of issues and challenges that are generally relevant for the other products. For instance, the consideration of starch is relevant to the other cereal-based foods, such as bread, sake and, of course, distilled grain-based beverages. The discussion of Saccharomyces and the impact of its metabolism on flavour are pertinent for wine, cider and other alcoholic beverages. (Table 1 gives a summary of the main alcoholic beverages and their relationship to the chief sources of carbohydrate that represent fermentation feedstock.) We can go further: one of the finest examples of vinegar (malt) is fundamentally soured unhopped beer.

The metabolic issues that are started in Chapter 1 and developed in Chapter 2 will inform all other chapters where microbes are considered. Thus, from these two chapters, we should have a well-informed grasp of the generalities that will enable consideration of the remaining foods and beverages addressed in the ensuing chapters.

Table 1 The relationship between feedstock, primary fermentation products and derived distillation products.

Raw material

Non-distilled fermentation product

Distilled fermentation derivative

Apple

Cider

Apple brandy, Calvados

Barley

Beer

Whisk(e)y

Cacti/succulents

Pulque

Tequila

Grape

Wine

Armagnac, Brandy, Cognac

Palmyra

Toddy

Arak

Pear

Perry

Pear brandy

Honey

Mead

Rice

Sake

Shochu

Sorghum

Kaffir beer

Sugar cane/molasses

Rum

Wheat

Wheat beer

Whisky is not strictly produced by distillation of beer, but rather from the very closely related fermented unhopped wash from the mashing of malted barley.

Whisky is not strictly produced by distillation of beer, but rather from the very closely related fermented unhopped wash from the mashing of malted barley.

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