Influence of Brine to Cheese Quality

Transcription

1 Summary and Discussion of a technical Article published by Agroscope Liebefeld-Posieux (ALP) Influence of Brine to Cheese Quality Name Präsentator, Seite 1, Name Präsentator, Seite 1, Dipl.-Ing. Markus Auly Partner Workshop Sept, 14th 2009, Weinfelden

2 Subject of the Presentation Overview over the article Targeted Readers: Cheese makers What brine problems can put my cheese quality in danger? Relevant Parameters of Brine Physical parameters Chemical parameters Biological parameters Discussion of disinfection approaches

3 Goals of the Presentation Discuss some microbiological basics using the example of brine Generate a awareness for potential difficulties Better general understanding of microbial Processes Platform for questions and discussion Potential Market for our (FBR2000)

4 Brine, what for? Overview Cheese Production Starting point: Raw milk Pasteurisation (except raw milk cheeses) Casein (+fat) precipitated (by Lab-ferment or acid) Jellylike mass is broken and put in a matrix Compressed loaf goes into brine (30 min 20 days) Maturation ( some days to some months) MOs important for formation of aromas Bakteria (zb B. linens Romadur) Yeasts Moulds (Camenbert, Roquefort, etc)

5 Brine, what for? What happens during brine bath? Cooking salt (sodiumchloride = NaCl) concentrations of ~15-25% (m/m) Concentration difference ( gradient ) Salt Cheese Water Brine Proteins, minerals Brine Makes up the culture medium for the brine flora

6 Microorganisms in brine 1 - What does the salt do? NaCl dissolves Na + and Cl - ions bind water Availability of water is reduced high salt concentration = dryness for MOs Water activity (a w ) is a measure for the availability of water Generally: Bacteria grow down to a w ~ 0,9 (ca. 12% NaCl) Moulds: ~ 0,8 (ca. 22% NaCl) Certain yeasts: ~ 0,6 (saturated NaCl solution)

7 Insertion - Extremophilie / Mesophilie MOs Extremophile MOs can grow under extreme conditions Mesophile MOs thrive in moderate environments EXAMPLES: Halophiles: grow in high salt conc. Halotolerantes: survive for some time Thermophiles: hohe temps ( until 100 C) Psychrophile: low temp. (until 2 C) Acidophiles: acidic environment (low ph) Xerophile: dryness etc.

8 Microorganisms in brine 2 - Microbial Parameters Various parameters have influence on which types and which quantities of MOs grow in a specific brine: Physikal (temp., stirring, UV-irradiation etc.) Chemical (salt conc., ph, lactic acid conc. etc.) Biological (MOs inhibit/support one another) Those parameters influence Total germ count Germ count of certain types of MOs

9 Microorganisms in Brine 3 - What types can grow? Typical NaCl-conc. of brine: 15-25% Bacteria generally until a w = 0,9 (=12%NaCl) Numerous Exceptions: Brevibacterium linens (ca. 15%) Staphylococcus aureus ( bis ca. 18%) Moulds, yeasts (bis ca. 21%) above 21% only specialised MOs extreme halophiles no danger from this type But: Many MOs, that cannot grow, will survive for some time!!!

10 Brevibacterium linens Brevibacterium linens gram positive, rod shaped bacterium is needed in surface maturation of certain cheese types desired MO Washed-rind cheeses ( Limburger, Romadour, Appenzeller) Degrades proteins on the surface charakterististic aroma

11 Listeria monocytogenes is ubiquitary (= is found everywhere in small conc.) Cause of listeriosis harmless for healthy people immunocomprimised persons very serious infection (cancer patients, AIDS, after surgery) can harm fetus in pregnant women Virtually all known infections via dairy products or meat Can survive in brine for some days (15-25%) Brine is potential source of contamination with listeria

12 Microorganisms in Brine 4 - Total Germ Counts Despite NaCl high TGC of some Mio CFUs/mL Staphylococci ( CFUs/mL) Mould spores ( CFUs/mL) Yeast ( CFUs/mL) Brine is potential source of contamination for undesired MOs: Flavour defects Optical defects Pathogens Regular disinfection is necessary!

13 Disinfection of Brine 1 - Through Cleaning Brine has to be cleaned regularly (wheyproteins precipitate sludge sediments) Cleaning Methods: Partial replacement Pressure filters (Getränkefilter, diatomaceus earth) Good clarification and germ reduction Membrane filtration Often used in larger factories Supplementary pufification methods only when such cleaning is not enough

14 Disinfection of Brine 2 - alternative Methods Heating: Danger of corrosion Contamination with heavy metals Problematic Chemical Disinfection: Only hydrogen peroxide (H 2 O 2 ) is applicable Chlorine disinfectants generate toxic residues Is only treating the symptoms and high danger of corrosion Is disadvised by the authors and UV Disinfection

15 Disinfection of Brine 3 - UV Desinfection UV Disinfection: Can generally be used Dissolved substances can strongly reduce efficency Immerged UV-lamp: Agitation is necessary, transparency must be low Optimal is a continuous flow-through system in which the brine is lead in a thin layer over (respectively: under ) the radiation source. descripton of our FBR-system UV Desinfection is described as the most promising method in the article

16 Conclusion Disinfection of brine is a complex topic Many influencing parameters (Temp, ph, type of cheese, etc.) Desired and undesiered MOs Brine is extremly corrosive Alternative Methods are considered as problematic (heat, chemical) UV might turn out to be the most suitable method on the long run need real life experience and further development Discussed some basics: a w -value, salt concentration, extremophiles, cfu, etc.

17 That was it Thank you for your attention! Any questions? Feedback?