Received Date: January 05, 2013; Accepted Date: January 27, 2013; Published Date: February 05, 2013
Citation: Sushma Rani T, Kavitha Abirami CV, Alagusundaram K (2013) Studies on Respiration Rates in Coccinia grandis (Ivy Gourd) at Different Temperatures. J Food Process Technol 4:217. doi: 10.4172/2157-7110.1000217
Copyright: © 2013 Sushma Rani T, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Ivy gourd is one of the indigenous vegetable grown in India. The edible part of the ivy gourd is fruit and are mostly used for culinary purposes and also consider as a nutritious vegetable. Though it is a nutritious vegetable, the shelf life of ivy gourd is only 3-4 days in room temperature and 7-8 days in refrigerated conditions. The research maturity index and respiration rate are important in designing a packaging material for extending the shelf life at different storage conditions. Measurement of Respiration rates were carried out by conducting experiments at different temperatures of 10, 15, 20, 30 and 40°C. The respiration rates were calculated as the rate of release of CO2 relevant to the rate of O2 consumption of ivy gourd. The CO2 production and O2 consumption is maximum at higher temperature of 40°C. The O2 concentration decreased from 19.5 to 10.41 percentages and the rate CO2 release increased from 0.60 to 19.33%. The predictive models were developed for calculating the CO2 release rate and O2 consumption rates.
Ivy guard; Respiration rate; Temperature; O2; CO2
Ivy gourd (Coccinia grandis) is a unique tropical plant that is a member of Cucurbitaceae family. The common names for Coccinia grandis fruit are ivy gourd, scarlet fruited gourd, Tindori, tindola and Kovaikai . It grows well in India, Thailand and in tropical areas such as Hawaii. The edible parts of plant ivy gourd are differing from place to place due to variation in food habit. In Thailand leaves are edible, in Hawaii both fruits and leaves and in India, raw fruits are mostly consumed as a vegetable. Two varieties of C. grandis are recognized; tender fruits are bitter in one variety and not bitter in another, and the latter is used in Asian cooking [2-4].
The raw fruits are used to prepare an array of delicious dishes like stir fries, stuffed curries, stews, pickles and salads . The tender green fruits are nutritious and are good source of protein, calcium, fiber and beta-carotene- vitamin A as precursor. The harvesting maturity of ivy gourd is determined by the fruit colour which changes from green to light green. The normal storage life is 3 to 4 days and 7 to 10 days at room and refrigerated temperature conditions respectively. The Ivy gourd turns to a pink color due to initiation of ripening and loses its weight due to rapid wilting during storage . The ripened pink colour fruits are not suitable for culinary preparations. The quality deterioration with less shelf life of ivy gourd is primarily due to continuous respiration resulting in the process of ripening after harvest. The control of respiration maintains of freshness and keeping qualities on the shelves.
Ripening is a complex physiological process that increases the softening, coloring, sweetening and aromatic compounds in most of the fruits and vegetables. The respiration is a metabolic process by which organic material in living cells are continuously broken down by utilizing O2 and evolving CO2, H2O and energy . The metabolic reaction during respirations is shown below:
C6H12O6+6 O2→6 CO2+ 6 H2O+ 686 kcal/mole (1)
The rate of any reaction can be determined by measuring the rate at which the substrates disintegration and the formation of new substrates. In all respiration, due to the biochemical reaction the stored food substrate like glucose will be converted into energy in the presence of oxygen. The loss of water is small during respiration compared to the very high water content of most harvested commodities especially fruits and vegetables. The increased carbon dioxide and decreased oxygen cause a reduction of the respiration rate of the fruit tissue. This reduces the energy available for chemical changes that occur in fruits and vegetables, resulting in lower rates of ripening and prolonged preripening storability of produce i.e. lesser the respiration rate longer is the shelf life of the fruit .
Respiration is affected by a wide range of environmental factors that include light, chemical stress (e.g. fumigants), radiation stress, water stress, growth regulators, and pathogen attack. The most important post harvest factors are temperature, atmospheric gas composition, and physical stress. Temperature has a profound effect on the rate of biological reactions like metabolism and respiration. For the potential benefits during storage and packaging optimization, the effects of these gases at particular temperature on respiration must be quantified for the selection of packaging and storage conditions. Measurements of respiration provide an easy, non-destructive means of monitoring the metabolic and physiological state of tissues.
To retain the harvest quality of the vegetable and for extending the shelf life, the research on determination of respiration rates at different temperature is conducted with the following objectives:
1. To determine the changes in the gas concentration for a particular time interval.
2. Determine the effect of temperature on the respiration rate of Ivy gourd.
3. To develop mathematical models to predict respiration rate of Ivy gourd.
The raw materials, ivy gourd are procured from the local farmer’s field located at Vallam, Thanjavur. The ivy gourds are plucked from the plants after 120 to 140 days of planting. Ivy gourd samples were harvested in the morning at typical commercial maturity (dark greencolored firm fruit) and transported within one hour under ambient conditions to the laboratory. The physical dimensions like size, average weight and bulk density are measured for the samples selected for the respiration studies. The glass bottle of known (700 ml) volume is taken as container for filling with ivy gourds, along with closure lid. The closure lid has a small hole which is covered with an air tight rubber holder to draw the gas samples from the container. M-Type seal is used for sealing the container lid outside to make airtight.
The environmental chamber (Model HTC-3003, LiBratherm Instrument Private Limited, temperature range-0.1 to 60°C with an accuracy of ± 1°C and relative humidity range from 0 to 99%) for different selected temperatures is used for respiratory studies. The PBI dansensor gas analyzer of model TYP83090138, head space analyzer is used for measuring the oxygen and carbondioxide gas concentrations of the respiratory samples.
Experimental set up
A sample lot of 350 g selected with uniform size and color free from defects were filled in 700 ml glass containers. The glass containers were closed with the metal lid having airtight rubber septum for drawing gas samples using needles. The glazy type seal was used for sealing the bottle. The glass containers were placed in the environmental chamber for different selected temperatures of 40, 30, 20, 15 and 10°C for the respiratory studies. The gas samples were drawn from zeroth hour and at every 30min intervals till the O2 concentration in the bottles fell below 1%. All experiments were replicated for three times and the mean values were obtained (Figure 1).
Respiration rates: The respiration rate of fresh ivy gourds stored at different temperatures is calculated using the following formulae given by Susana C. Fonseca  in terms of the O2 consumption rates and/or CO2 production rates:
V is the partial volume occupied by the ivy gourd sample inside the glass bottle pack (ml)
R is the respiration rate of ivy gourd sample, which expressed as volume of O2 consumed/CO2 produced (ml/kg-hr).
M is weight of the product (kg).
T is enclosed time of product in a container (hour).
Modeling: Considering the respiration rate as a function of the four factors influencing the respiratory kinetics (i=4) namely, O2 and CO2 gas concentrations and, time and temperature of storage, a model based on an exponential growth or decay function was proposed. A similar relation was also used to express the respiration rate in terms of CO2 evolution. The values of gas concentrations collected from all temperatures were analyzed by multiple regression analysis using SYSTAT 10.0 for determining the value of the model coefficients.
The sizes of ivy gourd vegetables varied from 2.5 to 7 cm. The average weight of one ivy gourd fruit is 1.5 to 3 g. The bulk density per kg of fruit is about 0.02345 m3/kg.
Changes in the concentration of gases with respect to time and temperature
The ivy gourd in the airtight glass container undergoes the metabolic reaction due to the respiration, shows the variation in the O2 concentration and CO2 concentration. The O2 concentration decreased and CO2 concentration increased with time. The changes in O2 and CO2 concentrations with time in a jar at 40, 30, 20, 15 and 10°C are presented in the table 1.
|Time (min)||Gas Concentrations of ivy gourd inside the glass bottles|
|O2 (%)||CO2 (%)||O2 (%)||CO2 (%)||O2 (%)||CO2 (%)||O2 (%)||CO2 (%)||O2 (%)||CO2 (%)|
|0||19.97 ± 0.12||0.60 ± 0.26||19.93 ± 0.06||0.80±0.36||20.03 ± 0.12||0.90 ± 0.30||20.07 ± 0.06||0.70 ± 0.17||19.93 ± 0.15||0.70 ± 0.17|
|30||17.07 ± 0.15||3.07 ± 0.12||17.13 ± 0.12||3.33±0.12||17.27 ± 0.31||3.10 ± 0.10||17.57 ± 0.32||2.87 ± 0.29||18.57 ± 0.61||1.80 ± 0.10|
|60||13.63 ± 0.25||5.03 ± 0.35||14.13 ± 0.32||5.47±0.12||15.30 ± 0.36||4.50 ± 0.53||13.73 ± 0.40||5.97 ± 0.21||18.13 ± 0.25||2.43 ± 0.15|
|90||11.73 ± 0.42||6.40 ± 0.26||12.17 ± 0.47||6.77±0.15||13.53 ± 1.12||5.73 ± 0.92||11.53 ± 0.38||7.23 ± 0.15||17.47 ± 0.55||3.33 ± 0.25|
|120||9.99 ± 0.38||7.47 ± 0.31||10.12 ± 0.70||8.33±0.31||11.97 ± 1.10||7.00 ± 0.36||10.08 ± 0.29||8.10 ± 0.20||16.90 ± 0.66||4.20 ± 0.26|
|150||8.53 ± 0.22||8.33 ± 0.21||9.35 ± 0.72||9.03±0.42||10.32 ± 0.60||7.97 ± 0.32||8.92 ± 0.41||8.87 ± 0.23||16.04 ± 0.75||4.97 ± 0.32|
|180||7.52 ± 0.16||9.47 ± 0.29||8.92 ± 0.74||9.33±0.42||9.91 ± 0.51||8.53 ± 0.60||8.40 ± 0.62||9.33 ± 0.15||15.67 ± 0.74||5.37 ± 0.25|
|210||6.43 ± 0.31||10.87 ± 0.84||8.51 ± 0.74||9.90±0.62||9.29 ± 0.70||9.07 ± 0.46||8.10 ± 0.71||9.60 ± 0.10||15.24 ± 0.75||5.90 ± 0.10|
|240||5.40 ± 0.20||12.47 ± 1.12||7.35 ± 0.86||10.77±0.81||8.26 ± 0.56||9.97 ± 0.81||7.25 ± 0.54||9.93 ± 0.29||14.54 ± 1.02||6.60 ± 0.36|
|270||4.43 ± 0.21||14.00 ± 0.17||6.70 ± 0.67||11.53±0.40||7.13 ± 0.06||10.77 ± 0.72||6.67 ± 0.55||10.30± 0.46||13.74 ± 1.02||7.47 ± 0.15|
|300||3.30 ± 0.10||15.77 ± 0.31||6.38 ± 0.53||11.97±0.35||6.48 ± 0.15||11.40 ± 0.72||6.15 ± 0.97||10.93 ± 0.65||13.01 ± 1.22||8.33 ± 0.21|
|330||1.97 ± 0.22||17.30 ± 0.40||5.92 ± 0.85||12.53±0.57||5.81 ± 0.37||12.20 ± 0.92||5.80 ± 0.90||11.27 ± 0.60||12.24 ± 1.28||9.20 ± 0.40|
|360||1.27 ± 0.40||18.33 ± 0.21||5.48 ± 0.76||13.23±0.64||5.11 ± 0.65||12.63 ± 0.90||5.36 ± 0.92||11.60 ± 0.50||11.30 ± 1.16||10.03 ± 0.40|
|390||0.67 ± 0.15||19.33 ± 0.38||5.06 ± 0.69||13.83±0.55||4.13 ± 0.83||13.00 ± 0.87||4.92 ± 0.74||11.90 ± 0.56||10.41 ± 0.98||10.83 ± 0.44|
Table 1: Gas concentrations at different temperatures of 40, 30, 20, 15 and 10°C of ivy gourd.
CO2 production rate
The CO2 production rate increased significantly with increase in temperature. There was a gradual increased concentration of CO2 with respect to increased time from 0 to 400min at same temperature due to the respiration of ivy gourd samples. The CO2 production was high at elevated temperatures compared to the low temperature. From the figure 1 the increase in CO2 production rate at 40°C compared with gradual reduction at 30, 20 and 10°C respectively was observed. According to R. Lakakul,  the rise in CO2 content in the package or inside the jar will increase the heat where there will be a chance of enhancing the rate of respiration and ripening for further time. Similar observations were noted in the respiration studies with increase in the temperature for increase in the respiration rate of ivy guard fruit-let (Figure 2).
O2 Consumption rate
The O2 consumption rate increased significantly with increase in the storage temperature inside the jar with ivy guard fruit let. As the time increased from 0 to 400 min of storage at same temperature, there was a gradual decrease in O2 concentration inside the glass jar environment. The loss of O2 and gain in the CO2 will spoil the product quality due to the internal heat evolved from the tissues by the process of respiration . From the figure 3 and the results obtained shows that the high O2 consumption rate at 40°C and the gradual decrease of O2 consumption rate at 30, 20 and 10°C respectively.
Modeling of respiration rate
The rate of decrease of O2 was found to follow an exponential pattern and observed to fit to a following empirical equation:
f is the O2 consumed by the ivy gourd
x is time measured for the O2 gas concentrations inside the galas bottles
a and b are constants.
Similarly the changes in the CO2 concentration with time were found to fit to an following empirical model:
f is the CO2 released by the ivy gourd
x is time measured for the CO2 gas concentrations inside the galas bottles
a and b are constants.
The R2 values of these equations were close to 0.9. The table shows the best fitting line for the O2 and CO2 concentration changes with time (Table 2).
|Temperature (°C)||Gas Concentration (%)||R||R2||a||b|
Where Goodness of fit is indicated by the R2 value, R = the multiple correlation Coefficient and a and b are constants.
Table 2: Statistical fitness for change in O2 and CO2 gas concentrations of ivy gourd during storage at particular temperatures.
The O2 and CO2 concentrations were predicted from 0 to 360 min for all experimental combinations. Using the equations (2) and (3) the predicted rate of respiration for the obtained gas concentrations was calculated. From the values, it was observed that the respiration rates for CO2 gas concentration at any temperature with increase in the time interval decreased. The CO2 production rate was faster at 40°C than the other temperatures. The reduction of respiration rates was noted at 15°C and 10°C. At 15°C there was a significant decrease of CO2 production rate and at 10°C there were fluctuations in the CO2 values which may be due to the occurrence of chilling injury of tissues (Table 3, Figure 4).
|Time (min)||RCO2 at 40°C||RCO2 at 30°C||RCO2 at 20°C||RCO2 at 15°C||RCO2 at 10°C|
RCO2 - Rate of respiration, which is expressed as volume of CO2 generated
Table 3: Respiration rates of Ivy guard for 30min time interval in ml kg-1 h-1.
From the results of this study the following major conclusions can be drawn:
1. The CO2 release and O2 consumption rates were faster during the initial hours of packing. The CO2 release rate was influenced by the O2 concentration prevailed inside the air-tight glass bottles.
2. The respiration rate was faster at higher temperatures (40°C) but remained stable at lower temperature (10°C). This shows that the respiration rate was less at lower temperature, which in turn increases the shelf life of the ivy gourd fruit.