Microorganisms in Food Industry

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Questions and Answers

What is the primary function of enzymes in fermentation?

To produce bacteriocins and vitamins

To convert lactate into glucose

To synthesize polysaccharides, proteins, and lipids

To hydrolyze polysaccharides, proteins, and lipids (correct)

Which of the following is NOT a benefit of fermented foods?

Enrichment of food substrates biologically with vitamins and essential amino acids

Increased risk of foodborne illness (correct)

Enrichment of the human dietary through development of flavors and aromas

Detoxification during food fermentation processing

Which type of microorganism is responsible for producing lactic acid in fermentation?

Yeast

Bifidobacterium

Mold

Lactic Acid Bacteria (LAB) (correct)

What is the end product of homofermentation?

1 mol of glucose into 2 mol of lactate Signup and view all the answers

Which of the following microorganisms is NOT a type of Lactic Acid Bacteria (LAB)?

Bifidobacterium Signup and view all the answers

What is the primary role of bacteriocins in fermentation?

To preserve food by inhibiting the growth of other microorganisms Signup and view all the answers

Which of the following is an example of a yeast used in fermentation?

Saccharomyces cerevisiae Signup and view all the answers

What is the purpose of fermentation in food processing?

To convert raw materials into fermented foods Signup and view all the answers

What is a key characteristic of a probiotic strain?

Ability to produce antimicrobial substances Signup and view all the answers

What is one of the benefits of probiotics in reducing colon cancer?

By reducing the growth of harmful bacteria Signup and view all the answers

What is a necessary step in the production of probiotics?

Fermentation Signup and view all the answers

What is a key factor in the competitiveness of a probiotic strain?

Ability to adhere to intestinal epithelia Signup and view all the answers

What is one of the effects of probiotics on the gut microbiota?

Antagonism against pathogenic bacteria Signup and view all the answers

What is a beneficial effect of probiotics on lactose intolerance?

Hydrolysis of lactose Signup and view all the answers

Which of the following acids provides an unfavourable environment for the growth of many pathogenic and spoilage microorganisms?

Lactic acid Signup and view all the answers

What is a characteristic of a probiotic strain that ensures its survival in the gut?

Ability to resist bile acid and digestive enzymes Signup and view all the answers

What is the primary mechanism of action of bacteriocins produced by LAB?

Depolarization of the target cell membrane Signup and view all the answers

What is a requirement for a probiotic strain to be considered beneficial?

Origin from the intestinal tract of healthy persons Signup and view all the answers

What is a characteristic of reuterin produced by strains of Lactobacillus reuteri?

It is an equilibrium mixture of monomeric, hydrated monomeric and cyclic dimeric forms of h-hydroxypropionaldehyde Signup and view all the answers

Which of the following is NOT a desirable property of bacteriocins produced by LAB for food preservation?

They are active and toxic on eukaryotic cells Signup and view all the answers

How can bacteriocins be used to supplement foods?

By using ex situ produced bacteriocin preparations Signup and view all the answers

What is a benefit of using bacteriocins as a food preservation method?

It permits the marketing of “novel” foods without compromising food safety Signup and view all the answers

What is the characteristic of Lactococcus, Pediococcus, and Streptococcus?

They produce only lactic acid. Signup and view all the answers

What is the main difference between natural fermentation and controlled fermentation?

The level of inoculation with starter culture. Signup and view all the answers

What is the purpose of cryoprotectant agents in concentrated frozen cultures?

To reduce cell death and injury during freezing and thawing. Signup and view all the answers

What is a common problem associated with starter cultures?

All of the above. Signup and view all the answers

What is the effect of antibiotics in raw material on starter cultures?

They inhibit the growth of microorganisms. Signup and view all the answers

What is the primary factor that affects the effectiveness of fermentation in controlling the growth of foodborne pathogens?

All of the above. Signup and view all the answers

What is the purpose of biopreservation?

To extend the shelf-life and improve the safety of food using microorganisms and/or their metabolites. Signup and view all the answers

What is the characteristic of Leuconostoc?

It produces equimolar amounts of lactic acid, acetic acid, CO2, and ethanol. Signup and view all the answers

What is the effect of a bacteriostatic agent on microorganisms?

Inhibition of growth and reproduction of microorganisms Signup and view all the answers

What is the minimum concentration of an antimicrobial necessary to inhibit the growth of a particular strain of microorganism?

Minimum inhibition concentration (MIC) Signup and view all the answers

What is the effect of a bactericidal agent on microorganisms?

Complete killing of a defined number of microorganisms Signup and view all the answers

What is a target of food antimicrobials?

All of the above Signup and view all the answers

What is a factor that affects the antimicrobials activity in food?

All of the above Signup and view all the answers

What is the lowest concentration of an antimicrobial able to produce complete killing of a defined number of bacteria?

Minimum bactericidal concentration (MBC) Signup and view all the answers

Why are food antimicrobials not a substitute for good sanitation in food processing plants?

Because they are not a substitute for good sanitation practices Signup and view all the answers

What is the effect of a bacteriostatic agent on the number of microorganisms?

No change in the number of microorganisms Signup and view all the answers

Study Notes

Beneficial Microorganisms in Food Industry

Microorganisms are used in the food industry in several ways, including:
- Actively growing cells for fermentation
- Metabolic by-products, such as bacteriocins, vitamins, amino acids, and Single-Cell Protein (SCP)
- Cellular components, such as enzymes

Fermentation

Fermentation is a process where raw materials are converted into fermented foods by the growth and metabolic activities of edible microorganisms
Microorganisms' enzymes, such as amylases, proteases, and lipases, hydrolyze polysaccharides, proteins, and lipids to produce nontoxic products with pleasant flavors, aromas, and textures

Benefits of Fermented Foods

Enrichment of the human diet through development of diverse flavors, aromas, and textures
Preservation of substantial amounts of food through lactic acid, alcoholic, acetic acid, alkaline, and high salt fermentations
Enrichment of food substrates biologically with vitamins, protein, essential amino acids, and essential fatty acids
Detoxification during food fermentation processing

Microorganisms Used in Fermentation

Lactic Acid Bacteria (LAB): Lactococcus lactis, Streptococcus thermophilus, Leuconostoc spp., Lactobacillus spp., Pediococcus spp.
Related bacteria: Aerococcus, Microbacterium, Propionibacterium, Carnobacterium, Non LAB Bifdobacterium
Yeasts: Saccharomyces cerevisiae, Saccharomyces spp., Zygosaccharomyces
Molds: Aspergillus, Rhizopus, Penicillium, Botrytis

Types of Fermentation

Homofermentation: produces only lactic acid, such as Lactococcus, Pediococcus, and Streptococcus
Heterofermentation: produces equimolar amounts of lactic acid, acetic acid, CO2, and ethanol, such as Leuconostoc

Types of Fermentation by LAB

Natural fermentation: carried out by natural microflora, such as Lactobacillus sp and Leuconostoc mesenteroides
Controlled fermentation: uses high numbers of pure culture of single or mixed strains or species of microorganisms, with controlled acidification

Starter Cultures

Concentrated frozen cultures: prepared by growing cells in a suitable medium, concentrating by centrifugation, and resuspending in a liquid with cryoprotectant agents
Freeze-dried concentrates: prepared by drying concentrated frozen cells under vacuum

Problems with Starter Cultures

Strain antagonisms: production of compatible strains to avoid strain antagonism
Loss of a desired trait: physical and chemical stresses can result in loss of a trait
Cell death and injury: ensuring a large number of viable cells and a short lag phase
Inhibitors in raw material: antibiotics, sanitizers, nitrite, or phosphate in cured meat

Factors Affecting the Effectiveness of Fermentation

Initial product pH
Buffering capacity and food composition
Nature and concentration of fermentable Carbohydrates (CHO)
Rate of growth of LAB and targeted pathogens

Biopreservation

Refers to the extension of the shelf-life and improvement of the safety of food using microorganisms and/or their metabolites
Organic acids, such as lactic, acetic, and propionic acids, provide an acidic environment unfavorable for the growth of many pathogenic and spoilage microorganisms
Production of a range of other antimicrobial metabolites, such as H2O2, diacetyl, reuterin, and reuterocyclin
Bacteriocins: proteinaceous inhibitors produced by LAB, acting through depolarization of the target cell membrane or inhibition of cell wall synthesis

Benefits of Bacteriocins

Generally recognized as safe (GRAS) substances
Not active and non-toxic on eukaryotic cells
Become inactivated by digestive proteases, having little influence on the gut microbiota
Show a bactericidal mode of action, usually acting on the bacterial cytoplasmic membrane
Permit the marketing of novel foods (less acidic, lower salt content) without compromising food safety

Probiotics

Beneficial effects on human health:
- Lactose hydrolysis (lactose intolerance)
- Reduce serum cholesterol level
- Reduce colon cancer
- Reduce intestinal disorders
Benefits thought to occur via:
- Biochemical effects (altering associated metabolic and enzymatic activities of resident harmful or developing pathogens)
- Competition for nutrients
- Competition for binding sites

What it Takes to be a Probiotic

Known microorganism origin from the intestinal tract of healthy persons
Stability during production, growth, or fermentation, concentration, freezing, drying, distribution, etc.
No adverse sensory properties
Genetic stability
Stability during incorporation into food/feed; pH, heat, drying, encapsulation, etc.
Competitiveness: stability at target site, resistant to bile acid and digestive enzymes, able to compete with normal microflora, resistant to antimicrobials produced by bacteria

Minimum Inhibition Concentration (MIC) and Minimum Bactericidal Concentration (MBC)

MIC: the minimum concentration of an antimicrobial necessary to inhibit the growth of a particular strain of microorganism
MBC: the lowest concentration of an antimicrobial able to produce complete killing of a defined number of bacteria, in defined media and within a defined time

Targets of Food Antimicrobials

Cell membrane or cell wall: increasing permeability and loss of cellular constituents
Inactivation of essential metabolic enzymes, protein synthesis, and genetic material
Transport mechanism for nutrients

Factors Affecting Antimicrobial Activity in Food

Level and type of microorganism
Storage conditions of food product, such as time, temperature, and humidity

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Description

Explore the role of microorganisms in food production, including fermentation and metabolic by-products. Learn how microorganisms contribute to food manufacturing and processing.