LSE 9A (drying)

• Of all the preservation methods,

  ______ is the simplest and

  the oldest

  drying
• Food is exposed to a _________ enough so that the

  _______ will be removed

  -hot temperature

  -moisture
• Removal of moisture from

  commodities to prevent

  _________

  -microbial growth
• Advantages of drying

  1.Preserves taste, appearance, and

  nutritive value of crop

  2. Dried foods take much less storage

  space than that of canned or frozen

  foods

  3. better quality due to controllable

  conditions

  4. better cooking quality due to uniform

  distribution of heat

  5. shorter processing time

  6. lesser space requirement

  7. better flavor

  8. contamination is prevented
• Methods of drying:


  Outdoors:

  -sun drying

  -solar drying

  Indoors:

  -Artificial Heat

  -Air Blast
• The food is placed on a screen,

  which is placed on top of blocks.

  The heat from the sun is used.

  Sun drying
• In sun drying the requirements are:


  -minimum temperature of 86℉

  -Below 60% humidity
• Uses foil and improved air ventilation to

  speed up the process of drying

  Solar drying
• Materials are dried through exposure

  to hot air coming from an oven or

  specially designed drier

  Artificial heat
• The food is dried by means of a fan

  driven by electricity or gasoline;

  requires at least 24 hours and

  applicable only to commodities with

  low moisture content

  Air blast
• Steps prior to crop drying

  1.Selection and sorting

  2. washing

  3. peeling

  4. cutting and slicing

  5. blanching

  6. Sulfur/acid treatment
• Select produce of the best quality

  -size, maturity and quality facilitates uniformity of drying

  Selection and sorting
• Removes dirt and unnecessary matters from

  the materials

  Washing
• ____________may be required to remove the

  wax-like coating of some fruits

  Cracking
• to control enzymatic activities

  blanching
• Sulfuring and mixing the fruit with ascorbic

  acid may be done to provide the fruit with

  antioxidants
• dried commodities are

  stored in bins or boxes to equalize

  moisture or to allow moisture to reach its

  desired level

  sweating
• dried commodities are

  packed for protection against moisture

  and contamination

  packaging
• -change in volume accompanied by various

  kind of damage (crushing of tissue, warped or distorted shape due to

  unequal shrinkage)

  -Can be prevented by slow drying of

  highly shrinkable material

  Shrinkage
• -due to overheating

  caused by extremely high temperature

  -Can be minimized by sulfite dip prior to

  drying

  Browning/Scorching
• -formation of hard,

  impermeable surface which prevents further moisture reduction

  -occurs when moisture evaporation from the surface is greater than

  the rate of moisture diffusion from the inner part

  -Can be prevented by controlling the

  relative humidity and temperature of

  circulating air


  Case hardening
• – caused by insect and microbial

  infestation and can be prevented by sulphur treatment

  Spoilage
• – formation of surface or subsurface

  granulation; affects the quality due to grainy or sandy

  part

  sugaring
• – caused by collapsed

  tissue after drying causing it to loose capability to

  rehydrate

  -can be prevented by storage under low temperature


  color detoriation
• – uses artificially produced heat in drying under controlled

  environment

  dehydration