Bioactive Compounds in Fermented Foods

Health Aspects

Amit Kumar Rai, Anu Appaiah K. A., Amit Kumar Rai, Anu Appaiah K. A., Amit Kumar Rai, Anu Appaiah KA

• Publisher: CRC Press
• Year: 2021
• Print ISBN:
  9780367136000
• eBook ISBN:
  9780429648571
• Topic: Technology & Engineering
• Subtopic: Biology
• Index: Technology & Engineering

The volume reviews different types of bioactive components associated with food fermentation and their impact on human health. The diversity of microorganism responsible for the production of different types of fermented foods and beverages includes bacteria, yeasts, and fungi. Biotransformation of food constituent by microorganisms occurs during fermentation processes for the production of fermented food and in the gastrointestinal tract by gut microorganisms. This biotransformation results in production of specific bioactive compounds that are responsible for a wide range of health benefits. The bioactive compounds discussed in this book includes polyphenols, bioactive peptides, fibrinolytic enzymes, gama-amino butyric acids (GABA) exopolysaccharides, probiotic, prebiotic, symbiotic and antinutritional factors. These bioactive compounds are responsible for health benefits such as antioxidant, antihypertension, antimicrobial, cholesterol lowering, anticancer, obesity and antithrombotic properties. Advanced research in the field of food fermentation and their health benefits have resulted in commercialization of some of the fermented foods as functional foods. The traditional fermented foods consumed in different parts of the world and their health benefits are discussed in detail and the book concludes with recent advances in microbial transformation during gut fermentation and their impact on human health. There has been increasing interest among researchers on the proposed title in the last decade and the book brings updated information on research and advances in different types of health benefits exhibited by bioactive compounds in a wide range of fermented foods.

Part I Introduction

CHAPTER1 Microorganisms Associated with Food Fermentation

Spiros Paramithiotis

Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos-75, 11855 Athens, Greece

Email: [email protected]

1. Introduction

Food fermentation may be defined as a microbe-driven bio-transformation of substrates adopted for human consumption into another form with modified organoleptic properties, enhanced shelf-life and, in most of the cases, nutritional value. These characteristics set the borderline between fermentation and spoilage; the latter includes non-desirable modification of sensorial properties and possibly toxic metabolic end products. Fermentation has been applied for centuries as a way to preserve excess foodstuff (e.g. lactic acid fermentation) or as a step in the production procedure of a variety of products (e.g. acetic acid fermentation for vinegar production, alcoholic fermentation for beverage production, sourdough for rye breadmaking, etc).

There are three parameters that direct the onset and evolution of the microcommunity that drives spontaneous fermentation: the type and microbiological quality of the raw materials, the selective agents added or released during processing and the incubation temperature. Proper control of these parameters is a prerequisite for successful fermentation. Depending on the main metabolic end product, as a consequence of the microbiota that drives fermentation, food fermentation may be divided into: (i) acid fermentation, the main metabolic end product is an organic acid, which is in the vast majority of cases lactic, acetic or propionic acid, the accumulation of which results in the drop of pH value and accumulation of acidity; (ii) alkaline fermentation, in which the main metabolic end product is ammonia, the accumulation of which results in the increase of pH value; and (iii) alcoholic fermentation, in which the main metabolic end product is ethanol. In addition, another type of fermentation exists but may not fit into the above categories – it is driven by moulds and therefore termed mold fermentation.

The aim of the present chapter is to provide an overview of the microbiota associated with each type of fermentation as well as the biotic and abiotic factors that ensure the presence and dominance of specific microorganisms.

2. Acid Fermentation

2.1 Lactic Acid Fermentation

Lactic acid fermentation is principally driven by lactic acid bacteria (LAB). Lactic acid is produced through homofermentative or heterofermentative catabolism (Fig. 1). Regarding the first, catabolism of carbohydrates to pyruvate takes place through the Embden-Meyerhof-Parnas pathway with pyruvate reduced to lactate through simultaneous NAD+ regeneration. Heterofermentative catabolism takes place through the pentose phosphoketolase pathway leading to the production of lactate, acetate and ethanol. The presence of molecules that may be used as electron acceptors may favour the production of one metabolite over another. A wide variety of substrates, including vegetables, fruits, cereals, meat and milk have been exploited through lactic acid fermentation, resulting in a wealth of products. Research was primarily focused on documentation of the production procedures and the ecological factors that direct the development of the microecosystem that dominates these fermentations. In addition, the properties that affect the safety, the nutritional value as well as the physicochemical and sensorial qualities of the final products, attracted specific interest. Soon, it was realised that LAB through their metabolic activities may produce bioactive compounds and, therefore, improve the functionality of these products, exerting, thus, health benefits to the consumers. The latter is currently the epicentre of intensive research with quite promising results. Lactic acid fermentation of fruits and vegetables, meat and milk is the most widely studied and therefore will be considered in this chapter.

Fig. 1: Glucose catabolism through the homofermentative (A) and heterofermentative (B) pathways. The reactions are catalysed by the enzymes: 1: glucokinase; 2: glucose-phosphate isomerase; 3: phosphofructokinase; 4: fructose-bisphosphate aldolase; 5: triose-phosphate isomerase; 6: glyceraldehyde-phosphate dehydrogenase; 7: phosphoglycerate kinase; 8: phosphoglycerate mutase; 9: enolase; 10: pyruvate kinase; 11: lactate dehydrogenase; 12: glycose-6-P dehydrogenase; 13: gluconate-6-P dehydrogenase; 14: ribulose-5-P-3-epimerase; 15: D-xylulose-5-P phosphoketolase; 16: acetate kinase; 17: phosphotransacetylase; 18: acetaldehyde dehydrogenase; and 19: alcohol dehydrogenase

2.1.1 Lactic Acid Fermentation of Fruits and Vegetables

An extended range of fruits and vegetables, according to geographical location as well as seasonal availability, have been used as substrates for lactic acid fermentation. However, only four of them have been worldwide recognized and commercially successful, namely fermented olives, fermented cucumbers, sauerkraut and kimchi.

In general, the production procedure usually involves four steps:

1. Collection and primary processing: Depending on the final product, the respective raw materials are collected and accordingly processed, e.g. for sauerkraut production, cabbage is washed and chopped. Other processing steps may include blanching, peeling, cooking or more specific steps, such as lye treatment that is required for olive fermentation.
2. Salting: Salt can be applied in a dry or a brine form. There is also a group of products that lactic acid fermentation is initiated without the need of a salting step (Gashe, 1987; Tamang et al., 2005). In dry-salting method, salt is applied directly on the chopped vegetables and brine is formed through the extraction of water and nutrients. In brine-salting method, an initial brine of 5–20 per cent, depending on the raw materials, is prepared and the respective fruits and vegetables are submerged. Extraction of water and nutrients takes place and finally equilibration is achieved after one day.
3. Fermentation: It usually takes place at ambient temperature. The micro-ecosystem development is accompanied by a series of physicochemical changes, according to the raw materials used.
4. Secondary treatment: This step includes any treatment that may extend the shelf-life and assist commercialisation of the final product, such as drying, pasteurisation, boiling, etc.

The microbiota that resides on the surface of intact fruits and vegetables consists mainly of members of the Enterobacteriaceae family and yeasts, though LAB are occasionally enumerated. Indeed, total aerobic mesophilic, Enterobacteriaceae and yeast/mold counts of cauliflower, green tomatoes and asparagus surface was reported to range between 3.5–5.7, 3.5–5.17 and 3.2–5.39 log CFU/g, respectively (Paramithiotis et al., 2010 a, 2014 a, b). LAB were only enumerated in the latter two cases, ranging between 3.14–5.32 log CFU/g. Dominance of LAB in the microecosystem that is developed through time is ensured by salting, incubation temperature and the microbiological quality of the raw materials. Effective control of the above parameters will result in enhancement of LAB growth during the first hours of fermentation, which is crucial due to concomitant acidity accumulation. The latter will prohibit antagonistic microbiota from developing in large numbers.

In Table 1, the lactic acid microbiota involved in representative lactic acid fermented products is shown. Certain LAB species are characterised by certain properties that justify their existence in fruit and vegetable fermentation. More specifically, Leuconostoc mesenteroides is known for a relatively shorter generation time, the abil...

Table of contents

• Cover Page
• Half-Title Page
• Title Page
• Copyright Page
• Preface to the Series
• Preface
• Table of Contents
• Part I: Introduction
• Part II: Health Promoting Components in Fermented Foods
• Part III: Traditional Fermented Products and Health Benefits
• Part IV: Recent Advances in Food Fermentation
• Index