1. Starter Cultures in Fermentative Processes
FOOD304 – Microbial Biotechnology
Starter Cultures in Fermentative Processes
Dr Stephen On
Associate Professor in Food Microbiology

2. Recap: Purpose of Fermentation
Preserve food particularly in warm climates
Production of food products (established/novel*)
*Novel may be a new taste or new attribute from using a different strain

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RECAP: Uses of fermentation
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Raw
material
Fermented
food
Benefit
Preservation
Milk
(Most materials)
Yoghurt, cheese
Enhancement of safety
Vinegar
Beer
Wine
Salami
Gari, polviho azedo
Soy sauce
Acid production
Acid and alcohol production
Production of bacteriocins
Removal of toxic components
Fruit
Barley
Grapes
Meat
Cassava
Soybean
Enhancement of nutritional value
Bread
Kimchi, sauerkraut
Nata de coco
Bifidus milk, Yakult,
Acidophilus yoghurt
Improved digestibility
Retention of micronutrients
Increased fibre content
Synthesis of probiotic compounds
Wheat
Leafy veges.
Coconut
Milk
Improvement of flavour
Coffee beans
Grapes
Cookie dough
Coffee
Wine
“Lager” cookies

4. Initiation of food fermentation
Strategy 1: Use indigenous microorganisms present in the raw material (natural or “wild” fermentation)
Raw milk
Wheat
Grapes
Environment
etc.

5. Wild Fermentation vs. use of Starter Cultures
“Wild” fermentations use yeast naturally present in/on the food being fermented to produce the food.
Tend to take longer (ferment can even stop if strains are not alcohol-tolerant) and flavour development is less consistent
Commercially available yeast starter culture strains are generally more dependable, more robust, tolerate higher alcohol content
Less complexity and less reflective of the region’s ecosphere

6. Can “wild” be industrial?
Yes!
Some wineries (eg. Mas Molla) still use only wild fermentation to produce wines.
“Lambic” beer is a speciality in the Flanders region of Belgium – wild fermentation is exclusively used. These beers are produced by breweries including Lindemans.
A combination strategy where wild ferments are completed by commercial cultures can also be employed. Purists decry the approach and suggest commercial strains would dominate the end result and colonise the brewing vats forevermore.

7. Screenshot is reproduced with permission from Sandor Katz, Website owner. Email 130116

8. Initiation of Food Fermentation
Strategy 2. Add starter cultures
Starter cultures may originate from:
The manufacturer (house strains isolated and maintained on site)
External commercial sources
In both cases the utility of the cultures are likely to be well established

9. Initiation of Food Fermentation
Strategy 3. A portion of the successful product used to inoculate fermentation in new batch of raw material
Beer
Some cheeses and cultured dairy products
Sour bread dough
Vinegar, etc.
Should contain the relevant number and type of microbes and have similar performance
Uncommonly used at commercial scale
Difficult to standardise

10. Industry-Grade Starter Cultures
Inoculated to overwhelm the existing flora
Establish desired changes
Consistent product quality
Acid production
Alcohol production and quantity
Antimicrobial compounds
Nutrient composition
Etc.
Predictable production - economics
Assurances for food safety and quality
Volume issue (cheese making)
Equinox, Creative commons BY-NC-SA license

11. Yeast Starter Cultures
Bread manufacturers largest users of yeast starter cultures
Several forms
Moist yeast cakes, active dry yeast packages, etc.
Saccharomyces cerevisae
Produce large amount of CO2
Fermented alcoholic beverages also use S. cerevisae
Different strains tend to be used (selected for flavor and alcohol tolerance) – it is possible to use breadmaking strains

12. No shortage of strains to choose from…

13. Mold Starter Cultures In cheese making Soy-derived fermented foods
Blue mold cultures consist of spore suspensions of Penicillium roqueforti and white mold cheese cultures contain P. camemberti
Soy-derived fermented foods
Tempeh: Prizopus microsporus
Miso and soy sauce: Aspergillus sojae and A. oryzae
By No machine-readable author provided. Brookie assumed (based on copyright claims). [GFDL ( CC-BY-SA-3.0 ( or CC BY-SA ( via Wikimedia Commons

14. Bacterial Starter Cultures
Most important bacterial starter cultures- Lactic Acid Bacteria (LAB)
Mostly belong to four genera
Lactococcus
Streptococcus
Lactobacillus
Leuconostoc
Dairy LAB represent the largest group
Mesophilic and thermophilic
S. thermophilus also used in Cheddar cheese making
L. lactis subsp. lactis occasionally incorporated in thermophilic cultures (Mozzarella)

15. LAB Starter Cultures
Lactic starters always include bacteria that convert sugars to lactic acid, usually:
Lactococcus lactis subsp. lactis,
Lactococcus lactis subsp. cremoris or
Lactococccus lactis subsp. lactis biovar diacetylactis.
Where flavour and aroma compounds such as diacetyl are desired the lactic acid starter will include heterofermentative organisms such as:
Leuconostoc citrovorum or
Leuconostoc dextranicum.

16. Lactic Acid Bacteria - Growth
The lactic acid bacteria are mesophiles:
they generally grow over a temperature range of about 10 to 40oC,
an optimum between 25 and 35oC.
Some can grow below 5 and as high as 45 oC.
Most can grow in the pH range from 4 to 8. Though some as low as 3.2 and as high as 9.6.
By M•Komorniczak -talk Illustration by : Michał Komorniczak This file has been released into the Creative Commons 3.0. Attribution-ShareAlike (CC BY-SA 3.0) If you use on your website or in your publication my images (either original or modified), you are requested to give me details: Michał Komorniczak (Poland) or Michal Komorniczak (Poland). For more information, write to my address: [CC BY-SA 3.0 ( via Wikimedia Commons

17. Functions of Other LAB Cultures
Lb. sanfranciscansis
ferment maltose, produce lactic acid to lower dough pH
Produce acetic acid and other flavor and aroma compounds
Sausage fermentation
Pediococcus acidilactici
Make lactic acid, reduce meat pH
Wine fermentation
Oenococcus oeni
Convert malic acid to lactic acid
Slight increase in pH, soften the overly acidic wines

18. Other Bacterial Starter Cultures – (Non- LAB)
Propionibacterium freudenreichii subsp. shermanii
Emmenthaler and other Swiss-type cheeses
Brevibacterium linens
Surface-ripened cheeses such as Limburger, Munster, brick cheeses
Micrococcus spp.
Some dry fermented sausage
Acetobacter aceti and related species
Vinegar manufacture
By No machine-readable author provided. Zubro assumed (based on copyright claims). [GFDL ( or CC-BY-SA-3.0 ( via Wikimedia Commons

19. Step-By-Step
FAO guidelines
Sources of starter cultures (cheese)