Michigan State University Extension
Preserving Food Safely - 01600512


  Some  fruits,  such as peaches, apples, pears and apricots
darken when exposed to air and during freezing.   Directions
for  such   fruits   list antidarkening treatment as part of
the freezing preparation.   Several  types of  antidarkening
treatments  are  used  because all fruits are not  protected
equally well by all treatments.                             

  Ascorbic acid                                             
  For most of the fruits that need antidarkening  treatment,
ascorbic  acid  (vitamin  C)  may  be  used.   This  is very
effective in preserving color and flavor  of  fruit and adds
nutritive value.                                            

  Ascorbic  acid is available  at  drug  stores  in  various
sized containers from 25 to 1,000 grams.  (Ascorbic acid may
be  obtained  also in  powdered form.)  One  teaspoon weighs
about  3 grams; thus  there  are  approximately  8 teaspoons
of  ascorbic acid in a 25-gram container.  In  the  recipes,
amounts  ascorbic acid are given  in teaspoons.             

  Ascorbic  acid tablets can be used but are more  expensive
and  more  difficult to dissolve than the  crystalline form.
Also  filler in the tablets may make the syrup cloudy.   The
amount  of ascorbic acid in tablets is usually expressed  in

  To use, dissolve ascorbic acid in a little cold water.  If
using tablets, crush them so they will dissolve more easily.

  In  syrup  pack, add  the dissolved ascorbic acid  to  the
cold  syrup shortly before using.  Stir it in gently so  you
won't  stir  in air.  Solutions of ascorbic acid  should  be
made up as needed.  Keep syrup in refrigerator until used.  

  In sugar pack, sprinkle  the dissolved ascorbic acid  over
the fruit just before adding sugar.                         

  In unsweetened pack, sprinkle the  dissolved ascorbic acid
over  the fruit and mix thoroughly just before packing.   If
fruit is packed in water,  dissolve  ascorbic  acid  in  the

  In fruit juices, add ascorbic acid  directly to the juice.
Stir only enough to dissolve the ascorbic acid.             

  In  crushed  fruits   and  fruit  purees,  add   dissolved
ascorbic acid to the fruit preparation and mix.             

  Ascorbic  acid mixtures                                   
  There  are   on   the   market    special   anti-darkening
preparations--usually  made  of  ascorbic  acid  mixed  with
sugar  or  with  sugar  and citric  acid.  If you use one of
these,  follow  the   manufacturer's  directions.   In these
mixtures  ascorbic  acid  is  usually  the  important active
ingredient.   Because of its dilution with other  materials,
ascorbic acid purchased in these forms may be more expensive
than the pure ascorbic acid.                                

  Citric  acid, lemon juice                                 
  For  a  few  fruits,  citric  acid  or  lemon juice (which
contains  both  citric  acid  and  ascorbic  acid)  makes  a
suitable   antidarkening  agent.    However, neither  is  as
effective as pure ascorbic acid.  Citric acid or lemon juice
in large  quantities will  mask the natural fruit flavors or
make the fruits too sour.                                   

  Citric  acid  is  available  at  drugstores.   When  using
citric  acid,  dissolve  it  in  a little  cold water before
adding  to the fruit according to directions for that fruit.

  For some fruits, steaming for a few minutes before packing
is  enough to  control  darkening.  Steaming  works best for
fruits that will be cooked before use.                      

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