THE STABILITY AND THE SHELF LIFE OF BEER

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THE STABILITY AND THE SHELF LIFE OF BEER

• Ceyda ÇELIK 060990505
• Elif ÖZDEMIR 090980513
• Serap GÜL 060980434
• Resul DILSIZ 060000401

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• The main components in brewing are germinated
  barley gtgtmalt, hops, yeasts and water
• The main characteristics of beer are flavor,
  color and clarity

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Chemical Deterioration of Beer

• The non-biological haze of beer is defined as
  chill haze when beer is chilled to 0?C and is
  redissolved when beer is warmed again to 20 ?C or
  above.
• the haze remains in beer at 20?C than it is
  called aspermanent haze.
• The mainly responsible group for non-biological
  haze of beer are proteins and polyphenols .

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Haze Formation

• Beer contains various proteins (polypeptides) and
  tannins (polyphenols) that can slowly react
  during shelf storage to form a colloidal complex.
  
• This complex becomes insoluble at the cold
  temperatures at which beer is stored and
  consumed.
• The result is formation of an undesirable
  cloudiness known as chill.

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Bitterness

• Flavor changes may develop before any haze
  formation.
• Bitterness in beer increases while the a-acids in
  hops are izomerized during boiling with wort and
  decreases with age of beer while sweetness
  increases

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Browning

• As a result of Maillard Reaction brown pigments
  called melanoidins are produced.
• This reaction is a serous problem for shelf life
  of beer, because it is also responsible for the
  stale flavor formation on storage.
• The low concentration of starting materials,
  anaerobic conditions in sealed bottle, the
  unsuitable pH value for browning, low temperature
  during storage may decrease the browning
  reactions in packaged beer.

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Microbiological Deterioration

• Beer is resistant to microbial spoilage
• low nutritionals values
• the presence of ethanol and other methabolic
  products of yeast
• low pH
• low redox potential
• capacity of bactericidal hop bitter substances.

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Microorganisms

• Lactobacilli, Pediococci, Enterobacteria,
  Aeromonas, Zymamanas, Acinetobacter,
  Corynebacterium and Bacillus are bacteria causing
  beer spoilage.
• Lactic acid bacteria are most dangerous
  microorganisms
• their microaerophilic nature,
• their relative indifference to free oxygen
• the acquisiton of tolerance to hop antiseptics
• ethanol concentrations up to 6
• low pH in beer

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• Lactobacilli cause spoilage characterized by
• silky
• dirty or buttery off-flavors
• Growth the in finished beer is limited by
  deficiency of amino acids in beer.
• Pediococci cause spoilage characterized by
• acid formation and
• off-flavor called sarcia sickness or sarcia
  odor
• Wild yeast contamination causes formation of
  haze, unfinable turbidity, excess gas, excess
  acidity and off- flavor. gtgt Saccharomyces spp.

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Brewing Process and Beer Stability

• Oxidation takes very important role for beer
  staling on storage and packaging.
• Brewers trying decrease oxygen pick up in
  packaging which can be obtain by using CO2 to
  transfer beer, deaeration of water for filling
  the filter.

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Materials and beer stability

• Materials effect the beer stability.
• The beer brewed from the proanthocyanidin free
  mutant showed stasfactory haze stability.
• Tetrahydro-isohumulones and p-isohumulones are
  not easy to be cleaved, so that beer brewed with
  these isohumulones is less susceptible to
  sunstruck flavor.
• These isohumulones have been already used to brew
  a light stable beer in some brewries

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Fermentation and beer stability

• Sulfite has an important role to protect beer
  from flavor staling on a shelf.
• Sulfite is produced in yeast cell during
  fermentation as an intermediate for a production
  of sulfur-containing aminoacids and axcreated
  from yeast into wort
• Flavor stability can be controlled by the
  combination of fermentation conditions, without
  harming the fermentation process and the flavor
  character of the fresh beer

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SO2 addition

• Antioxidant, antimicrobial agent, reduces the
  flavor impact of carbonyl compounds, it is an
  important constituent of beer.
• Masking the stale flavors that develop in beer
  during storage. neutralizes the staling carbonyls
  by forming irreversible adducts to them.
• Over time, the supply of sulfur dioxide gets
  used up and the protection of beer against the
  stale flavors diminishes with time and the beer
  begins to stale.

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SO2 addition

• The study done by Simpson et al.(1995) shows
• The rate of loss of both total and free SO2 is
  pseudo-first-order with respect to time.
• Reactions rate constant is increasing with
  increasing temperature in the rate of 0-40?C and
  it is dependent on the initial SO2 concentration.
  
• Half-life of SO2 in beer is about 6 months at
  25?C and storage of beer at 0?C reduces the rate
  of SO2 loss but it doesnt prevent it.

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Pasteurization

• In packaged beer, microorganisms can develop and
  form haze and off-flavors.
• Microbial danger have importantly diminished by
  the improvement of pasteurizatin technology.

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BESTPET

• Newly developed coating system doubles product
  shelf life
• A new development in Germany called BESTPET is
  supposed to double the shelf life of carbonated
  beverages
• Improved barrier properties with silica coating
  30-50 nanometer thick

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THANK YOU...