DEASON AND GRIERSON: CITRUS DEGREENING ROOM 259 Table 2. Deformation properties of two snap bean varieties. Variety Harvester Poda diameter inches,*36 Variety mean 1.2k.25.25.2k 2.26.2k.23 Sample number 3 k 5 Deformation -.31.31.26 inches.33.33 6.26.25 Mean.28.28.28b This study has indicated that Provider pods will deform more without breaking than Harvester pods of the same size. Previous research in Florida (8) showed that Provider was machine-harvested with fewer broken pods than other varieties. Two factors which may contribute to the lower pod breakage of the Provider variety during harvest ing are greater pod flexibility and lower detach ment force. Provider Vari ety mean.30.30.28.35.33.k7.k2.k3.37.ko.37 a Differences in deformation among pod diameters were non-significant. b Differences between variety means were significant at 1% level. L.S.D. =.03..35 36b into two pieces. The Harvester pods reached the snapping point after deforming only.28 inch. There was a slight tendency in some samples for greater deformation among inch diameter pods than in those of larger diameters, but this was not consistent among all samples. It should be pointed out that only sieve size 4 pods were in cluded in this preliminary study, and deformation relationships might be different for a greater range in pod sizes. LITERATURE CITED 1. Bledsoe, B. L. and A. H. Morgan. 1971. Picking mech anisms of snap bean harvesters. A.S.A.E. Paper No. 71-111. Pullman, Wash. 26 pp. 2. Bourne, M. C, J. C. Moyer, and D. B. Hand. 1966. Measurement of food texture by a universal testing machine. Food Technol. 20:522-526. 3. Curtis, L. M. and J. G. Hendrick. 1968. A study of the bending strength properties of cotton Btalks. Paper pre sented at A.S.A.E. meeting. Louisville, Ky. 4. Hoffman, James C. 1971. Injury of snap bean pods associated with machine harvesting and handling. J. Amer. Soc. Hort. Sci. 96:21-24. 5. Mohsenin, N. N. 1970. Physical properties of plant and animal materials. Gordon and Breach Science Publishers. New York. Vol. 2:734. 6. Pickett, L. K., J. B. Liljedahl, C. G. Haugh, and A. T. Ullstrup. 1969. Rheological properties of cornstalks subjected to transverse loading. Trans, of the A.S.A.E. 12:392-396. 7. Showalter, R. K. 1969. Detachment force for harvesting snap beans. Proc. Fla. State Hort. Soc. 82:115-118. 8. 1970. Detachment characteristics of snap bean pods and pedicels. Proc. Fla. State Hort Soc 83:248-252. HEATING OF CITRUS FRUITS DURING DEGREENING AND ASSOCIATED TEMPERATURE GRADIENTS WITHIN THE TYPICAL HORIZONTAL AIRFLOW DEGREENING ROOM Douglas L. Deason and W. Grierson IF AS Agricultural Research and Education Center Lake Alfred Abstract Temperatures were recorded in a large com mercial horizontal airflow degreening room which had been constructed based on current recommen dations of the Agricultural Eesearch and Educa tion Center, Lake Alfred and has performed to Florida Agricultural Experiment Stations Journal Series No. 4226. the satisfaction of packinghouse management. This room incorporated, for the first time, the concept of wall ducts to direct air individually to each row of pallet boxes. Low ambient temperature ventilation air admitted under the front curtain wall delayed the desired temperature rise within the room. The air temperature drop from rear to front of this room was 18 to 20 F early in the heating period, closing to a 7 F differential at the end of a 37-hour period of heating. Peel tempera ture lagged behind the air temperature by only 1 to 2 F. Deep pulp temperature lagged behind peel temperature by 1 to 5 F, this difference being greatest early in the heating period.
260 FLORIDA STATE HORTICULTURAL SOCIETY, 1971 Introduction and Literature Review Temperature requirements for citrus fruit dur ing degreening are crucial. For Florida citrus, the optimum temperature for degreening has been found to lie in the neighborhood of 85 F (2, 3). At temperatures below 85 F, the time required for degreening is increased markedly, while at temperatures above 85 F, both degreening time and subsequent decay are increased (2, 3). Thus, the legal maximum air temperature, when adding heat, for degreening of Florida citrus has been established at 85 F except when adding steam to maintain adequate humidity levels (5). Fruit size shrinkage associated with a weight loss of up to 2.9% has been observed for oranges degreened at 85 F and 85 to 90% relative humidity (R.H.) for 84 hours (4). Degreening periods should be as brief as possible to minimize this shrinkage and subsequent decay and to maximize packinghouse efficiency. To minimize degreening periods, it is essential to bring the fruit, and especially the peel, to the desired temperature as rapidly as possible. This Research Center has had a continuing program with regard to improvement of degreen ing room design. This has resulted in the horizontal aii-flow design, rather than the central airflow stack. The horizontal airflow degreening room (Fig. 1) has received rapid acceptance because of its adaptability to bulk pallet-box handling and its overall degreening performance. The packinghouses which have cooperated in this program report Pallet 11 Boxes REAR WALL I'd. ^_L 1 dl I - bud V Partition 2- Pallet Box Seal WALL DUCT DETAIL- TOP Figure 1. (A) Top view of wall ducts. (?) Airflow ma horizontal airflow degreening room with wall ducts. "V indi cates recommended position for ventilation. JL,/ faster, more even degreening, particularly with crops which are difficult to degreen. However, these results have been purely empirical and sub jective. In a number of installations where the room has been built with only one end opening, the last fruit in is necessarily the first fruit removed from the room. Moreover, when cold fruit is placed in the horizontal airflow degreening room, the fruit is warmed progressively from one end of the room to the other. Factors affecting the rate of movement of this warming front are length of room, volume of airflow per unit (90 lb. box) of fruit, initial fruit temperature, and air circulation within the pallet boxes, etc. It was conceivable that, with air delivery continuously at 85 F, the cold fruit at the location most remote from the air entry point would take many hours to reach 85 F. Information was inadequate to specify degreening room dimensions, airflow rate, and heating capacity necessary to achieve the desired fruit temperature within a specific period of time. The purpose of this study was to make a start on objective measure ments as a basis for future design criteria. It was decided that a first step toward improv ing degreening room design criteria was to better understand what temperature gradients existed in the horizontal airflow room and within the fruit throughout a cycle of heating and degreening. Experimental Methods Temperature measurements were obtained in a commercial degreening room at the locations in dicated in Figure 2. The room was 63 feet long by 35 feet wide with a 20-foot height to the false ceiling. This room was the first to incorporate the new concept of wall ducts to direct the airflow to the individual rows of pallet boxes. This feature improves degreening performance of partially filled rooms. For large rooms loaded row by row, this means that the room may be turned on as soon as filling is begun. Temperature data was also recorded in these wall delivery ducts and in the plenum chamber. This room was designed to provide 50,000 cubic feet per minute of air circula tion and 2.25 million Btu's per hour. Maximum room capacity was 7,200 field boxes (90 lb.) in pallet boxes. A 20-point recording potentiometer with built in reference cell was used with thermocouples con structed of ISA Type T (copper/constantan) thermocouple wire. Small thermocouple probes for insertion under the fruit peel and near the fruit
DEASON AND GRIERSON: CITRUS DEGREENING ROOM 261 Mass Average Location for Citrus Figure 3. Thermocouple locations in instrumented orange. The pulp temperature of the 'Hamlin' oranges when placed in the room was 60 to 65 F. Results and Discussion Figure 2. Thermocouple locations in pallet box stack: # - Under top layer of pallet boxes - 1, 2, and 3: - Above bottom layer of pallet boxes - 4, 5, and 6; A - 7 and 8, B - 9 and 10, C - 11 and 12. Thermocouples 1-6 recorded air temperatures, and 7-12 recorded fruit temperatures. center were constructed by cementing small thermo couples to 2-1/2 inch long, round toothpicks. Air temperature measurements were recorded for each of the six locations (points 1-6, Fig. 2), the thermocouple being located in the horizontal airstream channel formed by the contiguous pallets at the base of the pallet boxes. In the top row of pallet boxes at locations A, B, and C, an instru mented 3-1/4 inch diameter orange was placed approximately 6 inches deep in the pallet box of oranges. These 3 locations were at the top rear of the room, top center, and top front of the fruit stack respectively. The placement of the two thermocouples in each fruit was as shown in Figure 3; one inserted through the flesh out into the albedo of the fruit rind (fruit peel temperature), the second inserted approximately 0.75 the radial distance to the center (deep pulp temperature). The degreening room was filled during a 10- hour period with 5,000 boxes of fruit in 7-box pallet boxes (630 lb. net each). The fans, heat, humidity, and ethylene were turned on at the beginning of room filling; however, the front cur tain was not closed until filling was completed. The temperature traces shown in Figures 4, 5, and 6 are the results of temperature measure ments taken in the degreening room over a 37- hour period from completion of room filling to opening of the room. Temperature data on the instrumented orange in the pallet box at top rear of the room (points 7 and 8) was lost due to faulty thermocouple leads on the miniature thermocouples. Fruit temperature data for points 11 and 12 were not shown graphically, but are discussed later in the paper. Normally a temperature gradient exists be tween the surface of a fruit and the interior during the process of heating or cooling. Since the degreening process occurs in the peel, it is of interest to know the magnitude of this surface to interior gradient. Figure 4 presents the tem perature traces for fruit and air at the top center pallet box of the pallet stack. Trace 2 represents the temperature of the airstream beneath the pallet while traces 9 and 10 are the peel and deep pulp temperatures, respectively, of a fruit 6 inches below the top layer. The fruit at this location reached a peel temperature of 82 F after 24 hours of heating. The initial temperature gradient be tween peel and deep pulp temperature was 4 to 5 F, early in the heating period, closing to about 2 F later in the heating period. Bennett and Chace (1) have described the mass-average temperature point for citrus as lying in the equatorial plane at approximately 0.75 the radial distance from the fruit center. The mass average temperature represents the equilibrium temperature which a fruit would assume if no additional heat were added or lost. Since it is located much nearer to the peel than to the fruit
262 FLORIDA STATE HORTICULTURAL SOCIETY, 1971 9 Or 80 o 0) i70 Q> GL E ^60.Heated 8 in 7 hrs > Temperature af Air Beneath Pallet Skin Temperature Deep Pulp Temperature 3/4 of Radia I Depth > 6-30 Filling Completed-Room Closed I i i 630 12:00PM 1200 AM 1200 PM 8:00AM Fiarure 4. Air and fruit temperatures - top center of room - location B, Figure 1. center, the mass average temperature would more closely follow the peel temperature (trace 9) than did the deep pulp temperature (trace 10, Fig. 4). In order to reach the desired peel temperature, it appears that sufficient heating capacity must be supplied to raise the mass average temperature to the required degreening temperature. Figure 4 also indicates that, at the airflow rate occurring in this room (7.5 cfm/box), heat transfer to the fruit is very efficient, since little temperature differential exists between the air and peel temperatures. Similar gradients between air, peel, and interior temperatures existed at the top front location. However, at this location, the fruit peel tempera ture had increased to only 72 F at the end of 18 hours, and the highest temperature (81 F) achiev- 90 0) 80 o 2.70 E 60 Thermocouple Near Air Entry Thermocouple Center of Room (D Thermocouple Front of Room * 6:30 Filling Completed-Room Closed 6:30PM 12:00PM 12:00AM 12'OOPM 8'00AM Figure 5. Air temperatures beneath top pallet boxes.
DEASON AND GKIEESON: CITRUS DEGREENING ROOM 263 90-80 1701 1 60 Rear of Room Air Entry 50 <S> Center of Room Front of Room-Air Exit 6:30 Filling Completed-Room Closed 6*30PM I2'OOPM 12-OOAM 12'OOPM 8:00AM Figure 6. Air temperatures 26 inches off the floor (above bottom pallet box row). ed at this location was reached at the end of 25 hours. The temperature traces in Figures 5 and 6 in dicate the temperature drop of the heated air as it passed through the fruit mass. In line with the results shown in Figure 4, and previously dis cussed, the fruit mass average temperature was only slightly lower than the surrounding air temperature. The air temperatures at the rear and at the center of the room (Figs. 5 and 6) increased fairly rapidly to acceptable levels. Air temperatures at the front of the room, both near the floor and under the top pallet box, never reached the desired temperature. Temperatures at point 6, Figure 6 were particularly depressed as a result of the low temperature incoming ventilation air (Fig. 1). The period of rapidly increasing temperature for this point (Fig. 6) coincided with an outside ambient air temperature rise of approximately 10 to 12 F. It appears that the effect of the ventilation air (52 to 60 F) for the first 15 hours prevented the air temperature in the front half of the room from rising properly. This ventilation air rate was measured at approximately 4,500 cubic feet per minute or 5 times the necessary rate of 1 air change per hour (3). The maximum temperature drop of the air as it passes through the fruit stack was approximately 18 to 20 F and occurred in the time period immedi ately following closing of the room (Fig. 5). This in turn means that a maximum temperature rise across the coil face of approximately 20 F can take place. This 20 F rise in heated air tempera ture amounts to approximately 1.1 million Btu's per hour or 1/2 the installed recommended heating capacity. From this data, it appears that the pre sent recommendation of 0.75 Btu/ft3 of airflow is more than adequate. In addition, the large gradient which existed from front to rear of the room needs to be reduced. The use of higher airflow rates within the room to accomplish this will be investi gated. Conclusions 1. For this combination of room length, heat ing capacity, and air flow (velocity), a maximum temperature drop, from rear to front of the room, of 18 to 20 F was recorded. 2. Considering (a) that this room was near the maximum length of those having been con structed and (b) initial fruit temperature; this recorded air temperature drop implies a maximum temperature increase across the heating element
264 FLORIDA STATE HORTICULTURAL SOCIETY, 1971 (coil, etc.) of 18 to 20 F. This requires consider ably less heating capacity than is usually installed. 3. By industry standards, the room performed satisfactorily despite much greater temperature differences than suspected by commercial operators. 4. The cold ventilation air admitted under the front curtain can result in unfavorable degreening temperatures in the lower front portion of this type of room. Figure 1 indicates the preferred location for ventilation air entry. 5. The performance of these rooms with wall ducts was satisfactory to management throughout the entire packing season, even when operated only partially filled. This being so the rooms were operated, not as a batch operation, but continuously with fruit being moved in and out as convenient. Acknowledgements The cooperation of Haines City Citrus Growers Association is gratefully acknowledged. LITERATURE CITED 1. Bennett, A. H., and W. G. Chaee, Jr. 1970. Thermal properties and heat transfer characteristics of Marsh grape fruit. USD A, ARS Tech. Bull. 1413. 2. Grierson, W., and W. F. Newhall. 1953. Degreening conditions for Florida citrus. Proc. Fla. State Hort. Soc. 66:42.46. 3. Grierson, W., and W. F. Newhall. 1960. Degreening of Florida citrus fruits. Univ. of Fla. Agr. Exp. Stas. Bull. No. 620 p. 14-16. 4. Jahn, Otto L., and James Soule. 1967. Degreening response of color-sorted Florida oranges. USDA, ARS Bull. 51-14. 5. Regulations Pursuant to Chapter 601. May 17, 1965. Florida Statutes as amend. Reg. 105-1 13, Sec. (3). EFFECTS OF ETHYLENE AND TEMPERATURE ON CAROTENOID PIGMENTATION OF CITRUS PEEL Ivan Stewart and T. A. Wheaton University of Florida, IF AS I FAS Agricultural Research and Education Center Lake Alfred Abstract Carotenoids in the peel of harvested citrus in creased following treatment with ethylene. Im proved color resulted primarily from an increase in the amount of an orange-red pigment, cryptoxanthin, and a red pigment, jg-citraurin. Tempera ture influenced pigment accumulation. At 65 F and 75 F, rapid accumulation of both cryptoxanthin and jg-citraurin resulted in highly colored fruit. At 85 F, however, accumulation of /3-citraurin was inhibited which resulted in fruit having a lighter shade of orange color. This temperature sensitivity may explain the lack of substantial carotenoid formation during commercial degreening and the generally poor color of fruit grown in the tropics. Introduction The use of ethylene for degreening citrus fruit has been a common practice for over 50 years (1). However, its use for inducing carotenoid synthesis Florida Agricultural Experiment Stations Journal Series No. 4151, generally has not been recognized. Recently, we reported on increasing the carotenoids of citrus peel following treatment with ethylene (4). We found that 'Robinsons' changed from green to yellow and eventually to red if treated with ethylene at time of natural color break. The un treated fruit changed from green to yellow. The pigments which contributed mainly to the red color were identified as cryptoxanthin and y3- citraurin. Other varieties treated with ethylene have not responded in a similar manner. That is, fruit harvested at time of natural color break, degreened, without substantial increase in the red carotenoids. However, with increasing maturity on the tree, the use of ethylene markedly increased the caro tenoids in 'Orlando* tangelos, 'Temples/ and 'Pine apple' oranges. In most years, the fruit from the noi'th side of the tree is redder than that growing on the south side. In extreme cases, the fruit from the south side is graded out for the cannery or, if used, results in an unattractive pack. The purpose of this paper is to report on some of the causes believed to bring on this difference in color and a possible means of control. Materials and Methods Several techniques were tried for treating har vested fruit with ethylene. These included placing the fruit in commercial-type degreening rooms,