الفهرس 
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Abstract
In fruits and vegetables, certain physiological processes, such as heat transfer, respiration and transpiration, and quality properties, such as color, firmness or weight, are used as consumer-based criteria of acceptability and quality indicators.
A simplified model for heat and mass transfer and respiration rate in cool store with Anna apple was established to predict average temperature of apple and weight loss as well as respiration rate of apple.
The understanding of heat and mass (water) transfer at different positions in the cold room was achieved by interpreting the measured values of air velocity, temperatures (air and product), weight loss and calculated convective heat transfer coefficient.
Properties such as color, firmness, TSS, Reducing sugar and moisture provide valuable information for the monitoring of quality changes during cold storage period.
To achieve the objective of this research the following steps were carried:
1. Storage of Anna apple in cold room at 1 0C and two levels of evaporator fans speed (520 and 680 rpm).
2. Control of relative humidity inside cold room at 90 and 95 % ± 3% and use other cold room without control of relative humidity (55-70 ± 3 %).
3. Air velocity were measured (m/s) at different places (25 points repeated in three positions bottom and medium of pallet A and top of pallet B) to determine spatial distribution of these factors.
4. Temperature measurements were taken of apple (core, average and surface) and air temperature around apple at three different places in top of pallet B, medium and bottom of pallet A.
5. Determine of CO2 concentration during respiration process for apple inside cold room.
6. Simulate of heat, mass transfer and respiration rate during cool storage period by use mathematical models and validate these models.
7. Measure of energy consumption at each parameter.
8. Determine of some quality properties of Anna apple each 10 days during storage period such as weight losses, firmness, color, TSS and Reducing sugar.
The result obtained can be summarized as afollow:
1. Air velocity distribution inside cold room
The maximum air velocity was as 0.84 m/s for medium level located in center of cold room and near the front pallets (A and C) but the minimum air velocity at three level were range from 0 to 0.1 m/s at near of rear pallets (B and D), side walls and the corners at air velocity 680 rpm of evaporator fans speed.
Maximum air velocity at 520 rpm of evaporator fans speed was also at medium level by 0.55 m/s and minimum air velocity was 0.05 m/s at side walls.
Coefficient of variation was 152.7 and 161.9 %, 98.28 and 103.35% and 102.86 and 115.53% for the top, medium and bottom at 680 and 520 rpm of evaporator fans speed.
2. Heat transfer model results
Calculated convective heat transfer coeffecient
High convective heat transfer coefficients were calculated 11.15 and 8.173 W m-2 K-1 at 680 and 520 rpm of evaporator fans speed at the medium of A and C pallets, respectively. While the lowest convective heat transfer coefficients were observed at the top of the pallets B and D 5.028 and 3.78 W m-2 K-1 at 680 and 520 rpm of evaporator fans speed, respectively.
Cooling rate of Anna apple during cold storage
Good agreement between the predicted and experimental results was found for average temperature of Anna apple.
a) Cooling rate at 680 rpm of evaporator fans speed
The simulated average apple temperature decreased from 21.2 to 3 0C, 21.8 to 2.1 0C and 23.4 to 3.1 0 and from 23.2 to 2 0C, 22 to 1.8 0C and 23.4 to 2.9 0C and from 21.4 to 2.2 0C, 20.4 to 2.9 0C and 23.7 to 2.9 0C for bottom, medium for pallet A and top for pallet B at RH 90, 95 % and without control of RH (55-70 %), respectively. The lowest half-cooling time was less than 4.8 hours correspond to apples at the medium of the pallet A, while the longest half cooling times was 11 hours to apples at the top of the pallet B at RH 95 % and without control of RH (55-70 %).
b) Cooling rate at 520 rpm of evaporator fans speed
The predicted average apple temperature decreased from 23.4. to 3.4 0C, 21.8 to 2.8 0C and 24.8 to 4 0C at 90% of RH and from 23.5 to 3.6 0C, 23.5 to 2.9 0C and 25.1 to 4 0C at 95% of RH and from 23.1 to 3 0C, 21.8 to 2.4 0C and 23.9 to 3.3 0C at without control of RH (55-70%) for bottom and medium from pallet A and top from pallet B, respectively. Short half-cooling time was 8 hours correspond to apples at the medium of the pallet A and long half cooling times was 12 hours correspond to apples at the top of the pallet B for RH 95 % and without control of RH (55-70 %).
3. Mass transfer model of Anna Apple during cold storage
Good agreement was found between experimental and predicted data of weight loss of Anna apple during cold storage.
a) Weight loss at 680 rpm of evaporator fans speed The maximum weight loss (%) of about 5.53 % was observed experimentally at top of the pallet B while the predicted value is 5.76 % at without control of relative humidity (55-70 %) after 40 days preservation in the cold room. The minimum weight loss of about 1.74 % was observed experimentally at medium of the pallet A while the predicted value is 1.64 % at 95 % of RH.
b) Weight loss at 520 rpm of evaporator fans speed
The average of experimental weight loss after 40 day of initial cooling period was 3.15, 2.26 and 7.06 % at bottom of the pallet A while the medium of pallet A was 2.76, 1.98 and 6.71% while was 3.14, 2.30 and 7.38 % for the top of pallet B at 90, 95% of RH and without control (55-70%), respectively. While the average of simulated weight loss was 3.00, 2.23 and 7.08 % at bottom of the pallet A while the medium of pallet A was 2.90, 2.00 and 6.92 % while was 3.16, 2.23 and 7.21 for the top of pallet B % at 90, 95% of RH and without control (55-70%), respectively.
4. Respiration rate model
The maximum differences between measured and predicted respiration rate are 1.58 mLCO2kg-1h-1, 1.31 and 2.18 mLCO2kg-1h-1 at velocity 680 rpm and 1.42, 1.73 and 1.46 mLCO2kg-1h-1 at velocity 520 rpm for RH 90, 95% and without control of RH (55-70 %), respectively and so, this model was agreement between experimental and predicted data of respiration rate of Anna apple during cold storage.
a) Respiration rate at 680 rpm of evaporator fans
The predicted respiration rate decreased from 20.12, to 3.04 mLCO2kg-1h-1 after 11 hour from initial cooling storage, from 18.22 to 3.14 mLCO2kg-1h-1 after 12 hour from initial cooling storage and from 19.35 to 2.97 mLCO2kg-1h-1 after 13 hour from initial cooling storage at 90, 95% of RH and without control of RH (55-70%) during the first day, respectively. while the maximum respiration rate 20.22, 17.27 and 18.70 mLCO2kg-1h-1 was observed experimentally at 90, 95% of RH and without control of RH (55-70 %) during the first day, respectively.
The average predicted respiration rate was 3.12 mLCO2kg-1h-1, 3.14 mLCO2kg-1h-1 and 3.42 mLCO2kg-1h-1 during cold storage period at 90, 95% of RH and without control of RH (55-70 %).
b) Respiration rate at 520 rpm of evaporator fans speed
The predicted respiration rate decreased from 20.2 to 3.81 mLCO2kg-1h-1after 16 hour from initial cooling storage, from 20.08 to 3.53 mLCO2kg-1h-1 after 18 hour from initial cooling storage and from 20.01 to 4.38 mLCO2kg-1h-1 after 20 hour from initial cooling storage at 90, 95% of RH and without control of RH (55-70%) during the first day, respectively. while The highest respiration rate 20.22, 20.82 and 20.21 mLCO2kg-1h-1 was observed experimentally at 90, 95% of RH and without control of RH (55-70 %), respectively.
The average predicted respiration rate was 3.62, 3.5 and 3.83 mLCO2kg-1h-1 during cold storage period at 90, 95% of RH and without control of RH (55-70 %).
5. Energy consumption for cooling rooms:
The highest energy consumption was 62.65 and 198.54 kWh/mon at RH 90 and 95% for every evaporator fans speed (V1 and V2) respectively.
The lowest energy consumption was 44.65 and 180.54 kWh/mon at without control of RH (55-70%) for every evaporator fans speed (V1 and V2) respectively.
6. Quality properties of Anna apple during cold storage 6.1. Physical properties of Anna apple
The mean longest diameter, short diameter, width, weight, sphericity, surface area, true density of apples before the cold store were 57.05 mm, 51.3mm, 69.24mm,185.2 g, 0.98 and 85.8 cm2 and 878 kg/m3, respectively.
6.2. Quality properties of Anna apples cold storage as affected by evaporator fans speed
1. Firmness
The maximum firmness was 40.84 N and 27.58 after 10 days and 40 day cooling storage for 95% of RH at medium of pallet A and 680 rpm evaporator fans speed and it was significantly higher than in any of the other treatments.
The minimum firmness was 28.58 N and 20.04 after 10 days and 40 days cooling storage for without control of RH (55-70%) at top of pallet B and 520 rpm evaporator fans speed.
2. Color parameters
The mean value for color parameters L* ranged from 69.815±0.42 after 10 days to 62.875±0.42 after 40 day cooling storage while it ranged from 66.756±0.036 at RH 95 % to 63.633±0.036 at without control of RH (55-70%) also it ranged from 66.267±0.03 for 680 rpm (V1) to 64.452±0.03 for 520 rpm (V2) of evaporator fans speed and the mean value for L* ranged from 66.685±0.036 at the medium of pallet A to 64.039±0.036 at the top of pallet B, respectively, showed a significant (P<0.01).
The maximum values for L* was 73.20 and 72.00 at medium of pallet A and 95% of RH after 10 days from cold storage for 680 rpm (V1) and 520 rpm (V2) of evaporator fans speed, respectively while at the end of cold storage (40 day) was 67.17 and 64.21.
The minimum values for L* was 67.28 and 66.08 at top of pallet B and without control of RH after 10 days from cold storage for air velocities 680 rpm (V1) and 520 rpm (V2) of evaporator fans, respectively while at the end of cold storage (40 day) was 60.87 and 61.63 respectively.
The lowest mean value of parameter a* was observed at bottom of pallet A -2.833±0.177 and -2.430±0.177 at 90% of RH after 10 days from cold storage for 680 rpm (V1) and 520 rpm (V2) of evaporator fans speed, respectively while the highest mean value of a* was observed at medium of pallet A 1.343±0.177 for RH 90% and 1.673±0.177 at top of pallet B for without control of RH after 40 day from cold storage for 680 rpm (V1) and 520 rpm (V2) of evaporator fans speed.
The mean value for color parameters ΔE ranged from 6.866±0.41 after 10 days to 16.140±0.41 after 40 day cooling storage while it ranged from 12.343±0.036 at RH 90 % to 15.132±0.036 at without control of RH (55-70%) also it ranged from 12.752±0.029 for 680 rpm (V1) to 14.051±0.029 for 520 rpm (V2) of evaporator fans speed and it ranged from 12.350±0.036 at the bottom of pallet A to 14.249±0.036 at the top of pallet B, respectively.
3. Total Soluble Solids (TSS)
The maximum total soluble solids 16.5, 16 and 16.5 % were recorded in apple stored after 40 days for bottom and medium of pallet A and top of pallet B as compared to 15, 15 and 16.5 % was observed at 680 rpm (V1) and 520 rpm (V2) of evaporator fans speed for without control (55-70%) of RH respectively.
4. Reducing sugar
The maximum reducing sugar 12.08, 11.56 and 12.53 % was observed in apple stored after 40 days at 680 rpm (V1) of evaporator fans speed while was 12.65, 12.85 and 13.06% at 520 rpm (V2) of evaporator fans speed for 90, 95% (55-70%) of RH and top of pallet B, respectively.
The minimum value of reducing sugar was 11.62, 11.13 and 11.74 while was 12.41, 12.16 and 12.41 at 95% of RH and medium of pallet A at 680 rpm (V1) and 520 rpm (V2) of evaporator fans speed respectively.
7. Recommendations and conclusion
1- Good agreement between the predicted and experimental results was found for both final average Anna apple temperature, weight loss and respiration rate of Anna Apple inside cold room.
2- The higher air velocity (680 rpm) rates improve the evaporator air-side performance and include a uniform distribution of air temperature inside cold room.
3- Cooling storage of Anna apple at high and uniform relative humidity (95%) inside cold room lead to preserve properties quality.
4- It is important to control of the relative humidity inside cold room by use unit control of RH to maintain quality properties products freshly.
8. Recommendations for future work
These models have proven useful in prediction of heat and mass transfer during cold storage of fruits and vegetables. Additionally, model extension to predict gas atmosphere and fruit quality (for which sound submodels exist) could be undertaken. Thus, further steps could initially include:
- Incorporation of heat transfer modelling with mass transport modelling to better model long-term temperature differences in packaging systems and it is relation of product quality.
- Incorporating modification of other gases in the package atmosphere (such as CO2 and O2).