Demystifying Fermented Foods

Tuesday, September 10th 20191:00pm EST

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What They Are and How They Contribute to Healthy Diets

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Webinar Speaker & Disclosures

Maria L Marco, PhDProfessorDepartment of Food Science & TechnologyUniversity of California, Davis

Affiliation/financial interests (past 12 months)▪ Grants/research support: USDA, NIH, CDRF,

Innovation Funds, Denmark▪ Scientific Advisory Boards: Kerry Health and

Nutrition Institute, International Scientific Association for Probiotics and Prebiotics, International Probiotics Association, The Fermentation Institute, NIH Botanical Dietary Supplements Research Center in Pennington, LA

Outline

▪ Introduction and definition of fermented foods

▪ Brief description of how fermented foods are made and their characteristics

▪ Microbial and metabolic factors involved during the making of fermented foods

▪ Fermented foods and health benefits: clinical and epidemiological evidence

▪ Microbial processes and products contributing to health-impacting properties of fermented foods

History of Fermented Foods

Modern Day Cuisine

Fermented foods are foods or beverages made as a result of extensive microbial growth.

Definition

Sugars

Proteins, fats, polysaccharides

Incubate

Lactic acid bacteria Yeasts

MoldsLactic acid bacteria YeastOthers

ChopSaltSpicePackSoakHeat

Prepare

TemperatureOxygenpHWater activity

Ganzle Food Microbiology: Fundamentals and Frontiers5th Ed.; Editors: M. P. Doyle, F. Diez-Gonzalez, and C. Hill ©2019 ASM Press, Washington, DC

Thousands of Fermented Foods & Beverages

Characteristics of Fermented Foods

▪ lactic acid: kimchi, sauerkraut, yogurt, sausage, cheese

▪ alcoholic: wine, beer, spirits

▪ acetic acid: vinegar, kombucha

▪ mold-modified: tempeh, soy sauce, cheese, sausage

▪ CO2 (gas) containing: bread, kombucha, sparkling wines

Additional Details on Fermented Foods

▪ Fermentations can be spontaneous (wild) or initiated using “starter cultures” or a small portion of a prior ferment (backslopping)

▪ They are made using single (example: yogurt) or multiple (example: soy sauce) steps and can take hours, days, weeks to months prepare

▪ Depending on the food, a pasteurization step (heating) can be included (example: sourdough bread)

▪ There are no standards of identity for most fermented foods

Making Fermented Foods: Microbial and Metabolic Factors

Microbial Community Dynamics During Production of Fermented Foods

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LAB grew on the olives to ~106 cells /g

LAB were quantified on MRS medium containing Natamycin (25 ug/ml)avg ± stdev CFU/g of 5 replicates per processor are shown

Zaragoza, Bendiks et al

Lactic acid bacteria (LAB) are the most abundant microbes in olive fermentations

Microbial Community Dynamics During Production of Fermented Foods

Zaragoza, Bendiks et al

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yeast grew on the olives to ~1000 cells/g

Yeast were quantified on RBCA medium containing Chloramphenicol (100ug/ml)avg ± stdev CFU/g of 5 replicates per processor are shown

Yeast also contribute to olive fermentations

Culturable bacteria High-throughput DNA sequencing

Investigating Food Microbiomes

Food Fermentations are Dynamic Ecosystems

Zaragoza, Bendiks et al

Leuconostoc

Lactobacillus

Pediococcus

Candida

Pichia

Microbial Metabolism: Production of Flavor Compounds

Sugars lactic acid, acetic acid, acetaldehyde, diacetyl, CO2,

ethanol

ethanol, CO2

lactic acid

bacteria

yeast

Starch short-chained esters

polysaccharides mono/di-saccharides

molds

Bacillus

yeast

Proteins amino acids

peptides amino acids, amines

NH3 NH3

molds, Bacillus

(Clostridium) many

microbes

Fats (glycerol)

fatty acids ketones (esters)

moldsmolds

Microbial Metabolic Networks: More Than Just Flavor

Filannino et al 2018

Microbial Metabolism: Causes and Consequences of Different End Products

Ganzle 2015

Glu

Glu

▪ Lactic acid bacteria make organic acids which lower the pH of foods▪ To maintain intracellular pH, LAB can use amino acids and malate and this results in

the production of flavor and health-impacting compounds

Microbial Metabolism: Symbiotic Interactions and Fermentation Outcomes

Sieuwerts et al 2008

Yogurt fermentations

▪ Streptococcus thermophilus

▪ Lactobacillus delbrueckiisubspecies bulgaricus

Fermented Foods & Health Benefits: Clinical and Epidemiological Evidence

Human Studies on Fermented Foods

Cardiovascular diseaseFermented milk, fermented soy

Type 2 Diabetes Yogurt, fermented milk, kimchi

DepressionCoffee, fermented milk

InfectionFermented milk

Inflammatory bowel syndromeSourdough bread

ObesityKimchi, Chung kook jang, kochujang

Marco et al 2017

Made using Streptococcus thermophilus and Lactobacillus delbrueckii subspecies bulgaricus. Many yogurts contain other added strains.

▪ Reduced risk for T2D (observational; meta-analyses)

▪ Inverse association with adiposity factors (observational studies)

▪ Reduced risk for CVD (longitudinal)

Yogurt

Fernandez et al 2017Buziau et al 2019

DB: double blindCO: cross overRCT: randomized control trial

Made using different lactic acid bacteria species and yeast (kefir).

▪ Kefir: Improvement in bone mineral density in osteoporosis patients (DB-RCT)

▪ Kefir: Improved Helicobacter pylori symptoms (DB-RCT)

▪Fermented milk: Reduction in muscle soreness (DB-RCT)

Kefir & Fermented Milk

Tu et al 2015Bekar et al 2011Iawasa et al 2013

Sauerkraut is made using cabbage. Kimchi is made using cabbage, radishes, and other vegetables, fruits, and spices. Both are lactic fermentations (Leuconostoc; Lactobacillus).

▪ Sauerkraut: Reduced IBS severity scores (DB-RCT)

▪ Kimchi: improved insulin sensitivity, blood pressure, and metrics of adiposity (body weight, body mass) (DB-CO-RCT)

▪Kimchi: lower presence of atopic dermatitis (cross-sectional (KHANES)

Sauerkraut & Kimchi

Nielsen et al 2018Kim et al 2011An et al 2013

Sourdough bread is made with the help of yeast (Candida milleri, Saccharomyces cerevisiae) and lactic acid bacteria (Lactobacillus sanfransiscensis)

▪ Better tolerated by IBS patients, possibly due to lower concentrations of non-digestible oligosaccharides (FODMAPS) (DB-RCT)

▪ Improved GI tolerance (bloating, gastric volume) in healthy subjects (DB-CO-RCT)

▪ Some reduction in glycemic responses (RCT)

Sourdough Bread

Laatikainen et al 2016Polese et al 2018Korem et al 2017

Health-Impacting Properties of Fermented Foods

How Microbes Change Foods

Marco et al 2017

Preservation is enhanced

Safety is frequently improved

Transform food components

Synthesize new compounds

Increase numbers of living microbes

Preservation

Captain Cook was awarded a medal by the Royal Society for stopping scurvy with sauerkraut (1775)

Fermented foods typically have longer shelf-life times

▪ Increased organic acids (lower pH)

▪ Increased quantities of other antimicrobial compounds

▪ Reduced quantities of nutrients available for spoilage microbe growth

▪ This does not apply to all fermented foods (e.g. natto, soft cheeses)

Safety

Certain fermentations are acidic (pH < 4.5), decreasing the risk for foodborne illness

▪ Lactic acid bacteria (LAB) and acetic acid bacteria (AAB) acidify foods with lactic acid, acetic acid, and other organic acids

Possible safety concerns: ▪ Fermented foods made using molds have a higher pH and

therefore pose more of a safety risk (e.g. blue cheese, brie, tempeh)

▪ Other negative safety concerns for fermented foods include the production of biogenic amines

Transform Food Components

Reduce or remove toxic compounds and anti-nutrients in foods

Remove phytic acid (myoinositolhexaphosphate), an anti-nutrient in cereal grains that blocks mineral bioavailability (e.g. Fe, Ca, Zn, and Mn)

Improve food digestibility

• Reduce lactose concentrations (in dairy products)• Remove sugars that cause flatulence (raffinose and

stachyose)• “weaning foods” – (porridges after starch digestion)

Synthesize New Compounds

Increase vitamin & bioactive compound content in foods

• Bioactive organic acids• γ-Aminobutyric acid (GABA) • Conjugated linoleic acid (CLA)• Vitamins B9 (folic acid), • B12 (coalbumin), B2 (riboflavin),

B1 (thiamine)

Produceprebiotics

Compounds that modulate the gut microbiome to benefit human health

Increase Numbers of Living Microbes

Some fermented foods can increase the number of microbes consumed in a day by 100 to 10,000-fold

“Live and Active Cultures” is a good term

to apply to fermented foods

Some Microbes in Fermented Foods Survive Digestive Tract Transit

David et al 2013

Living Microbes ≠ Probiotic

▪ Probiotics are living microbes that when consumed in adequate amounts confer a health benefit

▪ Because fermented foods typically contain undefined microbial strainsthat have not been shown to benefit health, those foods should not be considered probiotic

▪ Dead microbes, microbial products, microbial components also do not come under the probiotic classification

Hill et al 2014

PHYLUM

CLASS

ORDER

FAMILY

GENUS

SPECIES

STRAIN

Firmicutes

DN-014-001

Lactobacillales

Lactobacillus

caseiShirota

BL23

Bacilli

Lactobacillaceae

Strain definition: A population of cells descended from a single isolate

But What is a Strain?

Bacterial Strains are Highly Diverse

78% genetically related

70% genetically related*

Staley 1997

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IL-1

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strain (random assignment)

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Anti-inflammatory IL-10 induced over an 8-fold range

Pro-inflammatory IL-12 induced over a 16-fold range

van Hemert et al 2010

Lactobacillus plantarum strains 42 L. plantarum strains incubated for 24 h with human peripheral blood mononuclear cells (PBMCs)

Variation in PBMC responses was greater than found between

different genera

Possible Overlap Between Probiotics and Microbes in Fermented Foods

▪ There can be genus and species overlap in effects on the human body

Hill et al 2014

▪ Some Lactobacillus species are both used as probiotics and used to make fermented foods (Lactobacillus plantarum, Lactobacillus casei)

Fermented Foods: Beyond Basic Nutrition

Yang et al 2018

Modulate the gut microbiota▪ prebiotics▪ organic acids▪ antimicrobial compounds

Improve barrier function▪ organic acids▪ secreted bioactive proteins

Stimulate immune responses▪ exposure to living microbes

Alter the gut-brain axis▪ neurotransmitters (GABA)

Key Takeaways

▪ Fermented foods and beverages are important components of human diets

▪ The unique textural and sensory qualities of fermented foods are a result of microbial growth and metabolism

▪ Health altering aspects of fermented foods are due to the ingredients in those foods combined with microbial growth and metabolism (transformation and synthesis)

▪ Just because a fermented food has living bacteria does not mean it is “probiotic”

▪ There are multiple ways in which microbial metabolites and living microbes in fermented foods might cause systemic effects via the digestive tract

More Research is Needed

▪ Many more human studies are needed to evaluate the health altering capacities of individual fermented foods and fermented foods as a food category

▪ Molecular, mechanistic research is needed to identify and verify the specific molecules in fermented foods (and living microbes) responsible for altering intestinal and systemic health

▪ Outcomes: Identification of health-benefiting fermented food formulations and personalized recommendations for adequate daily intake

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