3
of Oyster mushroom, that were still rare, to choice the right kind of bag plastic or to
design the proper packaging system. Therefore, the aim of this work is to study
the physiological behaviors of Oyster mushroom on several variations of
temperature storage and gas concentration.
2. Theoretical Approach
2.1 Respiration Respiration
is the
oxidative breakdown of complex substrate normally
present in plant cells -such as starch, sugars, and organic acids- to simpler
molecules such as CO
2
and H
2
O. Concomitant with this catabolic reaction is
the production of energy and intermediate molecules that are required to sustain the
myriad of anabolic reactions essential for the maintenance of cellular organization
and membrane integrity of living cells Kader and Saltveit, 2003. Oxygen which
is needed for oxidation must be available in the course of respiration process.
Respiration on fresh produce located on free atmosphere can be considered that
availability of oxygen is unlimited, therefore availability of oxygen does not
inhibits
the respiration.
Otherwise, limitation of oxygen availability on
surrounding atmosphere suppresses the rate of respiration Kader and Saltveit,
2003.
Depletion of
oxygen and
accumulation of carbon dioxide inhibit the reaction on internal tissue. Respiration is
enzymatic reaction that has common characteristic such as depend on substrate
concentration, pH, and temperature and of course the concentration of enzyme that
catalyses the reaction Metzler, 2002. Enzyme needs pH range 5.5 to 7.5 to
perform optimum activity on reaction. Besides, enzyme needs optimum reaction
temperature also Kader and Saltveit, 2003. Enzyme can be inactivated if the
reaction temperature very low otherwise enzyme will be denaturalized on too high
reaction temperature Belitz, Grosch, Schiberle, 2009. So, three factors that
influence the activity of enzyme are substrates concentration, pH and reaction
temperature. Heat is released
during respiration, 686 kcal or 2870 kJ heat is
released per 1 mole of glucose. Besides, 0.8-1 fraction of heat released is used to
heat the surrounding atmosphere or to increase temperature of product
Ooraikul and Stiles, 1991.
2.2 Respiratory quotient Respiratory quotient is defined as ratio
of production rate of CO
2
to consumption rate of O
2
. According to respiration equation in which mole O
2
consumed is equal to mole of CO
2
produced indicated by coefficient of every species that involve
in reaction.
+ 6 6
+ 6 +
Ooraikul and Stiles, 1991. From the definition it can be concluded
that the respiratory quotient is preferable to evaluate the respiration. Increasing on
magnitude of respiratory quotient indicates respiration is approaching to anaerobic
respiration or production rate of CO
2
is higher than consumption rate of O
2
. Kader 2002 suggested that respiratory quotient
on aerobic respiration range between 0.8 to 1.3 and the exact value is depending on the
intrinsic properties of product and the storage condition.
3. Method
3.1 Sample preparation Oyster mushroom was obtained from
UD. Agro Mandiri Yogyakarta located on Pakem Village. It took about 45 minutes
travelled by motorcycle. Mushrooms were harvested early in the morning, it was
about 5 o’clock, and then the harvested mushrooms were spread on the floor
covered by paper to reduce the water
4
which covers the mushroom’s surface. Mushrooms were weighted before packed
into box. Mushroom then transported to Operation Unit Laboratory of Agricultural
Technology Faculty of Gadjah Mada University. The last step was storing the
mushrooms at 5
C or 15 C for 1 hour to
equilibrate the mushroom’s temperature according to treatment temperature.
Three replications were prepared to investigate the respiration rate on different
storage temperatures. The plastic jars 9 liters were used on this work. Two holes
were made on the lid of plastic jars to facilitate
the measurement
of gas
concentration. 3.2 Respiration rate measurement
Mushrooms were weighted range
from 300 to 500 grams according to storage temperature and then were placed
in 9 liters plastic jars. Paraffin wax was used to cover the gap between the lid and
the body of the jar as well as at the hole at its lid. The mass of mushroom used were
±500 grams, ± 400 grams and ±300 grams for 5
o
C, 15
o
C and room temperature respectively. Those masses differences
were intentionally used for avoiding small gas concentration change on measurement-
time-range in which was difficult to measure due to lack of accuracy of
instruments.
Gas compositions
were measured by Cosmotector XP-314 type
Sensorex Oy, Finland for Oxygen
concentration and Cosmotector XP-318 type Sensorex Oy, Finland for CO
2
concentration. The instruments have an accuracy
of 0.1. Gas composition
measurements were taken every 4 hours, 3 hours and 2 hours for 5
C, 15 C and room
temperature respectively, until 1-2
oxygen level was obtained.
4. Results and Discussion
4.1 Respiration rate Respiration rate measured in this work
was not daily respiration development of harvested mushrooms but respiration rate
at different gas composition. The gas composition
change occurred
when oxygen was consumed and carbon dioxide
was produced by product. The mushroom stored
without interruption
and measurements were periodically conducted
during storage. Each data point in the figures below was taken to be initial gas
composition for the next measurement.
Amount of
measurement data
indicated the rate of gas composition change
inside the
jar’s head space.
Amount of measurement data time by period of measurement showed
the spending time for the head space to obtain
1 oxygen or 20 carbon dioxide level. The lowest storage temperature, 5
C, spent 52 hours to obtain those levels. This
period was longer
than period that mushrooms spent at 15
C with 18 hours and 14 hours
at room temperature.
Crossing point between O
2
and CO
2
curves occur at near 10 level. This indicates that
mushrooms spend equal time to obtain the half level of head space concentration and
also indicates that the ratio between O
2
consumption rate and CO
2
production rate approaches 1.
Figure 1
.
Gas concentration development at 5 C
data are taken every 4 hours
5 10
15 20
25
1 2
3 4
5 6
7 8
9 10 11 12 13 14 co
n ce
n tr
a ti
o n
v v
n
th
data [O2]
[CO2]
5
Figure 2
.
Gas concentration development at 15 C
data are taken every 3 hours
Figure 3
.
Gas concentration development at room temperature data are taken every 2
hours
Figure 1-3 show that rapid respiration occurs at initial storage of mushrooms.
Abundant oxygen on head space and field heat that still remain accelerate the
respiration.
Respiration continuously
decreases when oxygen is getting thinner and carbon dioxide getting thicker as well
as product temperature getting colder. Oyster mushroom respires rapidly faster
than 60 ml O
2
hr.kg, therefore mushroom Oyster is grouped in vegetables with very
high respiration rate Kader, 2002.
4.2 Respiration and temperature Data demonstrate that temperature had
major influence on Oyster mushroom respiration rate. Air temperature is the
most important variable because it tends to control flesh temperature of perishable
commodities Thompson, 2002. Lowering temperature to 15
C and 5 C could
suppress the consumption rate of O
2
76.4 and 95, respectively. Slight different
effect occurred to production rate of CO
2
. Lowering temperature to 15
C and 5 C
suppressed the production rate of CO
2
50.7 and 81.7, respectively. On the other hand, gas composition has minor
effects on Oyster mushroom respiration i.e, at room temperature respiration rate
decreases to 27.9. All of this value was calculated from the data taken at first
measurement of gas concentration. First measurement was considered indicate the
influence of temperature alone. It was different to next measurement which was
considered indicate the influence of temperature and gas concentration.
This value is as great as respiration of broccoli.
Relative to held in the ambient air, the reduction in respiration rate is about 28
for broccoli heads in 2 O
2
Kader and Saltveit, 2003.
Table 1.Respiration rate on 5 C, 15
C and room temperature storage
replication Consumption rate of O
2
Production rate of CO
2
Respiratory Quotient RQ
Ea kJmol
mlhr.kg mlhr.kg
O
2
CO
2
5 C
15 C
Room 5
C 15
C Room
5 C
15 C
Room
2.33 2.09
1
55.82 135.97
302.18 62.52
173.05 319.38
1.12 1.27
1.06
2
56.94 135.97
302.18 64.20
162.68 319.38
1.13 1.20
1.06
3 53.59
135.97 352.55
58.05 160.29
368.51 1.08
1.18 1.05
average
55.45 135.97
318.97 61.59
165.34 335.76
1.11 1.22
1.05
5 10
15 20
25
1 2
3 4
5 6
7 co
n ce
n tr
a ti
o n
n
th
data [O2]
[CO2]
5 10
15 20
25
1 2
3 4
5 6
7 8
co n
ce n
tr a
ti o
n v
v
n
th
data [CO2]
[O2]
6
Table. 2 Respiration rate at different O
2
concentration
n 5
C 15
C Room
[O
2
] R
02
[O
2
] R
02
[O
2
] R
02
vv mlO2hr.kg
vv mlO
2
hr.kg vv
mlO
2
hr.kg
1 21.00
56.38 21.00
135.97 21.00
318.97
2 15.95
22.05 15.50
90.64 18.47
323.47
3 14.00
23.45 11.83
79.93 15.83
296.72
4 11.90
18.42 8.60
89.00 13.30
419.70
5 10.25
8.93 5.00
70.87 9.83
281.08
6
9.55 17.86
2.13 8.65
7.40 228.55
7 7.75
12.40 5.57
230.03
8 6.50
11.16
9 5.50
8.93
10 4.70
10.12
11
3.85 8.03
12
3.05 8.27
13 2.30
8.16
Columns of Table.2 showed the influence of
O
2
concentration changes.
But, combination of temperature and gas
concentration changes gives the great influence on mushroom respiration.
4.3 Respiratory quotient RQ Respiratory quotient could be define
as the rate ratio of CO
2
production to O
2
consumption; CO
2
and O
2
could be
measured in moles or volumes depending on the substrate being oxidized. RQ values
for fresh commodities range from 0.7 to 1.3
for aerobic
respiration. When
carbohydrates are
being aerobically
oxidized, the RQ is near 1, while it is 1 for lipids, and 1 for organic acids. Very
high RQ values usually indicate anaerobic respiration in those tissues that produce
ethanol. In such tissues, a rapid change in the RQ could be used as an indication of
the shift from aerobic to anaerobic respiration Saltveit, 2004. The value of
the RQ presented in Table 1. Although has the various value at different temperature,
but the deviations is small. Those values were calculated from initial respiration
where the surrounding atmosphere was still rich in O
2
. Kader 2002 and Saltveit 2004 suggest that aerobically respiration
on fresh produces stored at physiological temperature range from 0.7
– 1.3.
Therefore, those values indicate
that respiration was aerobic. This conditions
continuously changes according to O
2
changes, but was still in the aerobically respiration range Table 3. Give more
attentions on value on 5 C and 15
C, they show that Oyster mushrooms was not
sensitive to O
2
low level or CO
2
high level. Kader 2002 suggest that mushrooms are
one of vegetables that respire highly but withstand to high level of CO
2
. Evaluation on mushroom appearance that are stored at
5 C and packed with plastic jar for 3 days
give the prove that they can preserve with low temperature and low O
2
concentration. The excessive accumulation of CO
2
12 inside the package can cause physiological injuries to the produce,
which in the case of mushrooms, results in severe browning Nichols and Hammond,
1973; Lopez-Briones et al., 1992 is not proven in this case. But authors suggest
that this fact need to be investigated further, because this research is not
intended to prove or to refuse that fact. Especially, the similar influences occur on
different species and different storage conditions.
4.4 Activation energy of respiration Activation energy of respiration used
to predict the respiration rate on other storage temperatures. Predictions of the
respiration rate of mushroom on different storage temperature are conducted by
taking the 5
C as reference temperature. From figure below we can see that the
influence of temperature has linear pattern.
7
The gradient of each linear equations come from linearization represents the activation
energy and universal gas constant ratio EaR.
Table 3. Respiratory quotient on different temperature and O
2
composition
5 C
15 C
Room
1.12 1.18
1.05 1.19
0.61 1.12
0.93 0.48
1.24 0.87
1.35 0.57
1.29 1.49
0.96 0.89
1.25 0.99
0.85 0.96
1.03 1.23
1.04 1.06
1.01 1.03
The
O
2
concentrations refers to Table 2
Applying the
Arrhenius’ law,
respiration rate of mushrooms
along physiological temperature can be counted.
= 0.28 .......a
= 0.25 .......b,
Where subscript on parameter RR and T represent value of respiration rate on
storage temperature T at condition 1 reference and storage temperature T will
be found. Equations a and b are the predictive equation for O
2
consumption and CO
2
production rate, respectively. With the activation energy Ea are 2.33
kJmol and
2.08 kJmol
for O
2
consumption and
CO
2
evolution respectively, prediction of respiration rate
of Mushroom Oyster at 5 C to 30
C is easy to count. This Arrhenius equation
assists the engineer to design of packaging system.
5. Conclusions
