Bakery technology

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Bakery technology

• Quality in the bakery
• Noël Haegens

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Bakery technology

• Qualitative aspects
• quality of bread
• staling
• microbiological aspects

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Bakery technologyintroduction

• as with a piece of music one doesn't listen to
  the notes but gets a complete impression. Bread
  is the same thing, one must get a complete
  picture composed of
• fysical characteristics (softness, length,
  weight, volume, crumb structure etc.)
• chemical characteristics (salt, fat content,
  water content etc.)
• microbiological characteristics (total count)
• organoleptic characteristics (taste, smell,
  colour, mouthfeel)

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Bakery technologyintroduction

• Positive quality
• More then the expected
• has no upper limit
• must be maximised

• Negative quality
• the disappointments
• the limit is zero defects
• must be minimised

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Bakery technologyintroduction

• a quality system can be product oriented i.e. the
  product must comply with a number of agreed
  specifications
• the quality system can also be process oriented
  i.e. the main aim is to manage, to improve and to
  certify the (production) processes.

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Bakery technologyintroduction

• the quality system can also be company oriented
  qaulity of all processes ? the organisation
  evolves towards a more professional organisation
• finally the quality system can also be "chain"
  oriented i.e. to manage all processes between
  commercial partners ? from the suppliers of raw
  materials to the final consumer (not necessarily
  the same as the customer)

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Bakery technologyquality improvement

• product improvement proces improvement
• the quality of the process is the
• MEAN
• the quality of the product is the
• RESULT

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Bakery technologyline capabilities

• only by using objective tools to measure quality
  parameters one can establish whether or not
  progress has been made in the process of
  continuous improvement
• each parameter however has a "natural" variation
  which is inherent to the process.
• LINE CAPABILITIES

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Bakery technologyfactors affection quality

• Factors affecting the quality of bread
• volume influenced by the flour ( ash content,
  protein content), the emulsifier (oxidantia,
  emulgator, enzymes), proofing (quantity of yeast,
  time, temperature, humidity), baking process.
• crumb structure flour (quality and quantity of
  the proteins), mixing (development of gluten
  network), mechanical treatment after scaling
  (moulding, rounding)

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Bakery technologyfactors affecting quality

• crust colour sugar content (added or as a
  result of enzymatic reactions), final proof
  (temperature, time, humidity), baking.
• softness of the crumb volume, crumb structure,
  composition of the bread improver, humidity of
  the crumb, baking curve.
• crustiness sugar content, baking curve, way in
  which the bread is stored after baking
  (temperature and humidity, the "weather").

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Bakery technologysensory evaluation

• when assessing the quality of a bread the
  assessor will look at
• the volume, the shape and the looks
• the crust
• the crumb

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Bakery technologysensory evaluation

• a good volume normally indicates a good bread,
  however the volume depends on
• the type of bread (white, rye, whole wheat...)
• the way it was produced (baked in tins or on the
  ovenfloor)
• local habits what's a good volume in Brussels
  isn't necessary a good volume in Paris

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Bakery technologysensory evaluation

• also the shape and looks will learn us something
  
• the shape, depending on the type of bread, should
  be regular, not too flat or too round
• the bottom (voet) should neither be concave nor
  too wide
• the closure (slot) is it well made, doesn't it
  distort the nice shape ?
• do the sides waste ? (taillevorming)
• amount of dusting flour ?
• incisions
• decorations (seeds) regularity, too much or too
  little ?

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Bakery technologysensory evaluation

• the crust is an essential part of the bread and
  plays a major role in the taste of course.
  However it also can tell us things about
• problems with the oven or baking curve crust
  can be too thick, too dark or too pale
• problems encountered during processing crust
  too hard or too soft, tearing of the crust (too
  little proofing), blisters, dark spots on the
  crust etc.
• Difference between crusty, hard and brittle

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Bakery technologysensory evaluation

• cut the bread with a good knife, smell and taste
  the crumb
• smell of yeast or raw dough (insufficient baked
  product)
• bread crumb easily absorbs foreign odours such as
  paint or gasoil
• taste cool, acidity (sourdough), salt, sweet,
  stale, yeasty

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Bakery technologysensory evaluation

• evaluation of crumb structure
• type of bread
• irregular crumb colour
• water marks
• make-up errors
• flour streaks
• too regular
• too coarse
• softness by touch
• resilience

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Bakery technologychemical fysical analysis

• moisture content overnight at 103C 2C
• salt content titration to determine chlorine
• sugar content GLC analysis of the different
  types of sugar (glucose, fructose, sucrose,
  lactose)
• fat content extraction with hexane/isopropanol.
  Determination of types of lipids and SFC (puls
  NMR).

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Bakery technologychemical fysical analysis

• ash content 650 700C
• Aw value water activity. Determination of free
  water
• crumb texture digital image analysis quantifies
  number and shape of cells, thickness of cell
  walls
• texture analyser softness by excersing know
  force on crumb until probe sinks 1 cm into the
  crumb

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Bakery technologychemical fysical analysis

• Differential scanning calometrie crystalline
  structure of starch can be reversed. This
  process requires heat. The amount heat needed to
  "refresh" the starch is a measure for staleness
• Fysical measurements weight, length, height,
  circomference, volume, shrinkage, thickness of
  the crust (UV)

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Bakery technology

• Qualitative aspects
• quality of bread
• staling
• microbiological aspects

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Bakery technologystaling

• bread is a delicate product it is
  "unbalanced", the physical - chemical differences
  that exist between the crust and the crumb are
  responsible for the typical characteristics of
  the bread. However as this "imbalanced"
  situation disappears, the bread looses its
  goodness.
• staling is a process which is not fully
  understood yet. First scientific study was made
  in 1856 but even today we still don't have a
  model which satisfactory explains all phenomenons.

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Bakery technologystaling

• staling starts as soons as the bread comes out of
  the oven. It's impossible to stop it (even when
  frozen). The only thing we can do is slow it
  down.
• staling has nothing to do with moisture loss. It
  has something to do with the crumb getting harder
  and that is a result of the retrogradation of
  starch (80 ?) and certain reactions between the
  starch and the proteins.

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Bakery technologystaling

• staling goes very fast between 7C and 7C.
  So it is not a good idea to keep the bread in the
  fridge. And when freezing bread one should use
  as little time as possible to get the bread from
  7C to a tempeture lower then - 7C (latent
  heat).

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Bakery technologystaling

• during staling a number of changes take place
• redistribution of the humidity between crumb and
  crust ? loss of crustiness
• changes in the organoleptic characteristics of
  the product taste, smell
• loss of softness which has - as said before -
  nothing to do with moisture loss.

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Bakery technologystaling
Crumb composed of starch granules
bricks continuous gluten network cement
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Bakery technologystaling

• After baking the starch has an amorphous
  structure but on cooling the starch gets a
  crystalline structure ? hardness
• Intimate contact between starch and proteins
  water migration from the gluten towards the
  starch ? the continous phase (the cement) dries
  out and the crumb becomes drier.
• This explains why amylases are considered as
  crumb softeners (there is less starch and more
  dextrines)

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Bakery technology

• Qualitative aspects
• quality of bread
• staling
• microbiological aspects

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Bakery technologymicrobiology

• theoretical the bread is not sterile when it
  comes out of the oven. It will however not get
  mouldy when packed in extremely hygenic
  circumstances (clean room technology).
• only one bacteria can survive the baking process
  namely Bacillus subtilis ? rope
• "bleeding bread" Serratia mencescens which
  forms a red pigment in foods which are rich in
  starch.

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Bakery technologymicrobiology
Penicilium mould Bacillus subtilis Rhisopus
stolonifer
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Bakery technologymicrobiology

• the microbiological shelflife of bread can be
  extended by one (or the combination of two or
  more) of the following methods
• physical methods pasteurisation, freezing,
  modified atmosphere packaging or radiation
  (?-rays)
• chemical methods addition of vinegar, sorbates,
  propionates, alcohol (delays staling)

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Bakery technologyconclusion

• the production of bakery products is, as all
  other fermentation processes, a very delicate
  process in which apparently unimportant details
  have an enormous effect on the quality of the
  product.
• imitate or copy an existing product is virtually
  impossible

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