Biomedical Engineering Reference
In-Depth Information
Fresh water loss
: A major factor in fresh mushroom deterioration has been
water loss and subsequent loss of weight. Loss of water is determined by
the environment and can be reduced significantly by use of film-wrapped
packaging.
102
Browning
: Whiteness is one of the most important aspects of fresh
Agaricus
mushroom quality. However, mushrooms are very sensitive to browning.
Mushroom deterioration is marked by brown discoloration of the mush-
room surface. Browning is caused mainly by the oxidation of phenolic
substances, which is catalyzed by polyphenol oxidase (PPO); controlled
or modified atmosphere storage can be helpful to slow this process. Sapers
et al.
115
used browning inhibitor solutions and found that the most effective
treatment was a combination of sodium erythorbate, cysteine, and EDTA
at pH 5.5.
Texture
: At harvest, mushrooms grown properly are firm, crisp (resist defor-
mation), and tender (easy to shear or chew), but subsequently in posthar-
vest deterioration they soften and toughen.
116
This is apparently caused by
chitin synthesis in cell walls (toughening) and loss of cell turgency due to
changes in membrane permeability (softening) after harvest.
Flavor and aroma
: Flavor is one of the most important quality attributes
contributing to the widespread consumption of mushrooms. The flavor
substances of mushrooms can be classified into (1) non-volatile compo-
nents such as amino acids and nucleotides, and (2) volatile compounds
such as 1-octen-3-ol and 3-octanone. The amino acid fraction of mush-
rooms, consisting of alanine, arginine, aspartic acid, glutamic acid, gly-
cine, and lysine, is probably responsible for some aspects of flavor, but
all nitrogenous components contribute to some extent to the typical mush-
room flavor. In addition, mushrooms contain relatively high levels of free
glutamic acid, which is known to be a flavor enhancer. Several aroma
compounds are produced by the Maillard reaction such as furans, pyrones,
cyclopentenes, carbonyls, acids, aldehydes, sulfur compounds, pyrroles,
and pyridines.
29
Charpentier et al.
117
quantified the flavor volatile and
aroma compounds of shiitake mushrooms (
Lentinus edodes
).
M
ETHODS OF
I
MPROVING
S
HELF
L
IFE AND
Q
UALITY
Due to the high perishability of fresh mushrooms, several methods have been
investigated to extend shelf life and to retard the deterioration processes in harvested
mushrooms.
Irrigation Treatment with Calcium Chloride and Stabilized
Chlorine Dioxide (Oxine)
A successful reduction of the initial bacterial population and an increased shelf life
of mushrooms is accomplished by the addition of stabilized chlorine dioxide (oxine)
or calcium chloride, to irrigation water during cropping.
102
However, a significant
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