cheese starter cultures.pdf
Post on 29-Sep-2015
9 Views
Preview:
TRANSCRIPT
-
Cheese starter cultures
Ian Powell Dairy Innovation Australia 23rd October 2014
-
Cheese-making is not new Fragments of cheese strainers
Traces of organic molecules indicate presence of milk fats in strainers from 7,000 years ago
Salque et al., Nature 493, 522525 (2013) Dunne et al., Nature 486, 390394 (2012) Evershed et al., Nature 455, 528-531 (2008)
-
What were early cheeses like? Historical assumptions:
No deliberate use of coagulant Enzymes from use of stomachs as vessels to carry milk?
No deliberate use of starter cultures Natural milk flora Micro-organisms from GI tract
Of the animal the stomach came from or from human drinkers
Micro-organisms from skins used as vessels to carry milk Some carry-over from batch to batch
In storage vessels and cheese-making equipment
-
What knowledge did they have? Whatever they did .
They learnt that following certain procedures usually led to an edible, tasty product with better keeping qualities than liquid milk
They learnt that failing to follow the correct procedures often led to a foul-tasting, inedible product (or worse)
-
What knowledge did they have? Whatever they did .
They did not realise that they were some of the earliest adopters of enzyme processing and microbial biotechnology to generate a food with physical, nutritional and hedonic functionality
They did not realise that they were making use of temperature control, acidification, removal of fermentable sugars, partial dehydration and lowering of water activity as components of a prototype multiple-hurdle food preservation and safety plan
-
What knowledge did they have? Whatever they did .
They just did it.
-
Process diagram based on the description given by Columella. Fox et al, Cheese Chemistry, physics and microbiology (Elsevier, 2004)
Lucius Iunius Moderatus Columella ca 4 ca 70 CE
-
By the middle ages there were many established regional cheese styles (and manufacturing techniques) and extensive trade ..
But where are the starter cultures?
-
Starters became part of the magic Poorly controlled, highly variable, risky
Natural milk cultures Milk is incubated under conditions that favor the growth of naturally occurring (thermophilic) lactic acid bacteria, then used as starter.
Back-slopped starter Use some of a previous product batch as starter.
Whey cultures Starter is produced by incubating cheese whey under conditions that favor the growth of desirable (thermophilic) lactic acid bacteria.
Powell, Broome and Limsowtin, Encyclopedia of Dairy Sciences, 2nd edition (Elsevier, 2011)
No magical balance of organisms, but targeted process control to influence the development of desirable cheese microflora (even if no-one knew)
-
..and then the 19th century came
Louis Pasteur. Archives Photographiques, Paris Joseph Lister, 1st Baron Lister. Wikimedia Commons Lactobacilli. Bottazzi and Bianchi
Building on work by Henle, Schwann, Latour and others, in 1856-57 Pasteur connects yeasts and bacteria with alcoholic fermentation and its spoilage
1873-77 Lister isolates Bacterium lactis and demonstrates its role in acidification and curdling of milk
1884-90 Storch researches starters for butter and cream, leading to commercial supply of starter cultures in 1891
-
20th Century starters
Powell, Broome and Limsowtin, Encyclopedia of Dairy Sciences, 2nd edition (Elsevier, 2011)
Undefined mixed cultures (propagated in cheese factory)
Cultures (typically descended from artisanal cultures with desirable properties) are sequentially subcultured at the cheese factory.
Undefined mixed cultures (maintained in laboratory)
Cultures (typically descended from artisanal cultures with desirable properties) are preserved and propagated under controlled laboratory conditions.
Defined-strain starters
Laboratory-purified selected strains, free of microbiological contaminants, preserved and propagated under controlled laboratory conditions, then blended to give a mixed culture with desired properties.
-
The rituals are old, but the science is
relatively new.
http://www.wga.hu/art/zgothic/gothic/3a/2trade03.jpg
-
What is a starter culture? ..in 50 words or less
A cheese starter culture is a prepared culture that contains one or several strains of microorganisms at high counts, being added to bring about a desirable enzymatic reaction (e.g. fermentation of lactose resulting in acid production, degradation of lactic acid to propionic acid or other metabolic activities directly related to specific product properties). ISO 27205:2010 (IDF 149: 2010) Fermented milk products - bacterial starter cultures - standard of identity.
-
Photo modified from Bottazzi and Bianchi (1984)
What do cultures do?
-
Photo modified from Bottazzi and Bianchi (1984)
What do cultures do?
We now have enzyme studies and metabolic maps, genome sequences, transcriptome analysis, proteome studies ...... What does the cheese taste like? How has culture use changed?
-
The present and the future Understanding what cultures are
and what they do (strains alone and together in mixed cultures, different species in core or on surface, etc) is fundamental to future targeted culture and cheese innovation
...but, frankly, we just want good
cheese at a reasonable price. How do starters contribute to that?
-
Useful (?) definitions
Primary culture Primary starter, acid producer, starter Responsible for acid production in the
cheese make Contributes to flavour development Some have notable secondary characteristics
(e.g. heterofermentative cultures)
-
Examples of cheeses and related primary starters
Gobbetti et al. 2007
-
Useful (?) definitions
Secondary culture Secondary starter, adjunct, ripening culture No significant contribution to early acid production Influence / dominate flavour development, gas production, etc Characteristic cheese properties develop over time Added at same time as primary starter Incorporated into curd Added later Applied to surface, spiked etc
-
Examples of cheeses and
related secondary starters or
adventitious secondary microflora
-
Useful (?) definitions
How useful are these definitions? Traditional cultures include everything in one
culture .. except for the environmental contaminants
Modern cultures tend to split up the functions into multiple functions Why?
-
Practical (and profitable) solutions
Complex mixes are difficult to grow Variable, inconsistent Impossible to change growth conditions
without altering the balance of culture components
Single components can be grown more reliably (and cheaply) and then blended
but that makes complex blends expensive So ... Defined cultures are the trend
but the loss of complexity .......
-
How do we restore complexity?
Starter + secondary cultures Starter for acid and basic flavour
Trade activity for flavour? Secondary for
Specific flavour notes Surface ripening (bacteria, fungi)
This gives you complexity and control but is it as complex as it should be? industrial cheddar is a good example
-
What about raw milk flora?
An excellent source of non-starter organisms Are these significant contributors to flavour in
raw milk cheese? Can we capture them and tame them (and
turn them into starters/adjuncts)? ...without losing complexity
-
Regional/farm-specific milk flora
Repeatedly propagate to encourage acidifiers and other acid-tolerants
Check purity
Establish seed stocks
Trial cheese-making Laboratory / cheese manufacturer
Product assessment
Commercialisation
-
Regional/farm-specific milk flora
Microbial composition analysis Community DNA profiling
Purification of representative safe organisms Purify and identify
Assembly of defined culture blend(s) Assemble, check and establish seed stocks
Production of trial defined culture blend(s) Prototype cultures of commercial quality
Trial cheese-making Laboratory / cheese manufacturer
Product assessment Sensory and instrumental analysis; community profiling
Commercialisation
-
What about raw milk flora?
-
Collection, selection, application and management of bacterial starter cultures
-
Culture collectionA biodiverse archive from which cultures are drawn for characterisation, development and industry use
Single (pure, defined) strains Undefined mixed-strain cultures
Culture composition Conventional microbial analysis and DNA methods Species and strain analysis of dominant types
Strain identification DNA-based methods Species classification Strain relationships
Strain blends, rotation and replacement Design blends, rotations and potential replacements Confirm performance, flavour and texture impacts Trial cheese manufacture Advice to culture users
Strain characterisation Performance testing Flavour impact Texture/appearance impact Antibiotic resistance Biogenic amine production Assessment of growth, survival and activity under production/storage conditions
Phage sensitivity Insensitive (known phages) Select resistant variants Phage-host infectivity table
Culture characterisation Performance testing Flavour impact Texture/appearance impact Antibiotic resistance Biogenic amine production Assessment of growth, survival and activity, and batch composition variability under production/storage conditions Trial cheese manufacture
Phage sensitivity No inhibition (known phages) Select resistant variants Phage-host infectivity table
Culture rotation and replacement Design rotations and potential replacements Advice to culture users
Sample and data feedback from cheese-maker to culture supplier
Phage detection Whey testing
Phage collection Archive of phage diversity Used in phage sensitivity screening and selection of phage-resistant variants
Phage analysis Host range testing and virulence assessment Identification, grouping and evolution analysis
Phage-resistant strains or mixed cultures
Emerging genomic analysis techniques can be used to characterise defined and undefined cultures
-
Current trends in cultures Increasing separation of culture functions
Use of adjuncts to achieve flavour definition Novel blends
Streptococcus/Lactococcus Higher activity at lower cost (phage & flavour effects)
Blending to re-create traditional complexity Without the quality and safety variability
Unique blends Your cheese, your culture
Demand for greater definition Species and strain typing Biochemical (flavour) potential Safety concerns, especially for new species
-
Current trends in cultures Genomics, proteomics, metabolomics
Genes, gene expression, predictive biochemistry Aid to strain selection and blending
Still relatively new and expensive Examples are in the public domain Not economic to do for every strain/blend/culture Practical verification of predictions needed
Metagenomics etc Prediction of properties of mixed cultures on the basis
of the genomic potential of constituent strains Better understanding of the complexity and
dynamics of traditional cultures
-
Current trends in cultures
Safety of cheese flora Culture composition largely based on traditional
practices; non-starter adventitious flora undefined Most organisms have never been subjected to
formal safety assessment Most culture types in current use have
demonstrated their safety through years of use (GRAS/QPS) rather than through pre-release laboratory or clinical analysis
-
Current trends in cultures
Safety of cheese flora Rational basis for use
Generally Regarded as Safe (US FDA) either through scientific procedures or, for a substance used in food before 1958, through experience based on common use in food.
Qualified Presumption of Safety is being adopted by European Food Safety Authority (EFSA): rational risk assessment for the continued use of many traditional types of microorganisms in foods in the absence of any formalised safety testing program.
-
Current trends in cultures
Genetically modified strains Laboratory GM work only for over 30 years Useful for defining important culture properties
Provides the analytical tools for new methods of culture characterisation
A guide to potentially useful natural variants Requires long-term commitment to get from
experiment to application of knowledge Approved release of GM strains for cheese-
making not likely in the foreseeable future
-
Culture delivery to the cheese vat
Bulk starter or direct-to-vat concentrate Starters must grow and survive the process Composition, convenience, capability, cost
Culture batch reproducibility important Acid-producing activity Flavour development etc
-
Culture delivery to the cheese vat Recent innovations
Frozen pelletised concentrates Cheaper delivery of blended cultures
Membrane systems to remove growth inhibitors Old idea, new technologies (e.g. electrodialysis) for
better culture growth Aerobic growth systems for LAB
Applicable to some species; supplemented conditions High-density growth without inhibitors
-
Preparation and long-term storage of frozen/freeze-dried seed stocksLaboratory scale
Pure strains or undef ined culturesQuality tested
Growth of large-volume starterPreparation by culture supplier
Concentration of cultureCentrifugation
Freezing/freeze-drying Culture blending if required Performance and quality tested Supplied to cheese factory
Cheese manufacture
Scale-upSequential scale-up of growth volume (mother/intermediate cultures)
Can be quality tested and f rozen/f reeze-dried for later use
Growth of large volume starter Bulk starter preparation in cheese factory Blending of strains at point of inoculation or af ter separate growth
Chilled, quality tested before use
In-house inoculaFor use by culture supplier
Bulk starter inoculaSupplied to cheese factory
Sample and data feedback from cheese-maker to culture supplier
-
Bulk starter or Direct-to-Vat? The real question is about outsourcing
Do you DIY? Which parts of your production process do you
outsource? Why? Cost? Safety? Reliability? How much control do you want, and what
limitations of design are you willing to accept? Does the scale of your business justify the
capital expenditure needed to grow bulk starter with high levels of control?
How long-term is your investment strategy?
-
Culture application
A partnership of culture supplier and cheese-maker Communication essential
Understand each other (needs and capabilities) Both require expertise Risk: Fundamental knowledge and available
culture products are growing but practical expertise to apply them is not keeping up?
Slide Number 1Cheese-making is not newWhat were early cheeses like?What knowledge did they have?What knowledge did they have?What knowledge did they have?Slide Number 7Slide Number 8Starters became part of the magicPoorly controlled, highly variable, risky..and then the 19th century came20th Century startersThe rituals are old,but the science is relatively new.What is a starter culture?..in 50 words or lessWhat do cultures do?What do cultures do?The present and the futureUseful (?) definitionsExamples of cheeses and related primary startersUseful (?) definitionsExamples of cheeses and related secondary starters or adventitious secondary microfloraUseful (?) definitionsPractical (and profitable) solutionsHow do we restore complexity?What about raw milk flora?Slide Number 25Slide Number 26What about raw milk flora?Collection, selection, application and management of bacterial starter culturesSlide Number 29Current trends in culturesCurrent trends in culturesCurrent trends in culturesCurrent trends in culturesCurrent trends in culturesCulture delivery to the cheese vatCulture delivery to the cheese vatSlide Number 37Bulk starter or Direct-to-Vat?Culture application
top related