Department of Food Technology and Nutrition
Mimeo Report 57-1
TOMATO MATURITY, SIZE, AND FIRMNESS RELATIONSHIPS AND THE USE OF
VOLUME-FILL EQUIPMENT VS HAND PACKING OF TOMATOES
R. K. Showalter
Florida Agricultural Experiment Station
The study of maturity, as related to quality, of tomatoes was con-
tinued this year with emphasis on the effect of size at harvest on the
maturity and firmness, and the effect of volume-fill equipment on the
pack and injury of the tomatoes.
Fruit size has long been considered as one criterion for judging the
maturity of tomatoes while they are still green in color. On February 13,
1956, the Florida Tomato Marketing Agreement and Order first regulated the
size of tomatoes shipped from Florida. If the immature tomatoes are the
smallest in size, they could easily be eliminated from marketing channels.
The Florida Tomato Committee requested that the Experiment Station conduct
tests on the rate of ripening of different size tomatoes.
Two crates of each of the five most common sizes of tomatoes were
obtained from commercial harvests at Immokalee on March 30, 1956, through
the cooperation of the Florida Tomato Committee. Each tomato was hand
sized to eliminate any inaccuracies of the machine sizing. The measurements
of the 7 x 8's through 5 x 6's are shown in Table 1. The tomatoes were
ripened at 68-72OF at the Gulf Coast Experiment Station, in cooperation
with Mr. D. G. A. Kelbert. At two day intervals the firm ripe f d
each size were counted. The ripening period extended from 4 to _days.
The results, in terms of mean days to ripen, are shown in Table
Table 1. Rate of Ripening of Different Size Tomatoes
Variety Date Sizes* of Tomatoes
Harvested 7x8 7 x 7 6 x 7 6 x 6 5x6
Homestead 3-30-56 Number of Tomatoes 377 312 249 204 153
**Mean Days to Ripen 16.2 15.9 15.4 14.4 12.8
Rutgers 3-30-56 Number of Tomatoes 405 341 272 202 152
**Mean Days to Ripen 16.9 17.0 15.4 13.0 11.7
Rutgers 4-6-56 Number of Tomatoes 53 55 52 51 --
**Mean Days to Ripen 11.0 16.0 16.5 13.0 -
Homestead 4-6-56 Number of Tomatoes -- 287 252 178
**Mean Days to Ripen -- 13.9 12.3 10.5
Jefferson 5-18-56 Number of Tomatoes 710
**Mean Days to Ripen Size 6 x 6 and larger 11.5
7 x 8 1 7/8 in. 2 1/8 in.
7 x 7 2 1/8 2 9/32 "
6 x 7 2 9/32 2 17/32 "
6 x 6 2 17/32 2 7/8 "
5 x 6 2 11/16 3 3/16 "
**Mean days to ripen equals the sum of days to ripen times tomatoes at each ripening period divided
by total number of tomatoes.
:A A sJJ
On April 6, seven additional boxes of Rutgers and Homestead tomatoes
of four sizes were obtained at Immokalee and transported to a 700F ripening
room at Gainesville. The same procedure was followed with these tomatoes
and the results are in Table 1. The rate of ripening is also shown for
the six cartons of Jefferson tomatoes obtained at Ruskin in connection
with the volume-fill test. These fruit were 6 x 6 and larger size and
the average ripening period of 11.5 days approximated that of the other
lots of 6 x 6 and 5 x 6 tomatoes.
The results, in general, indicated that the smallest tomatoes required
the longest time to ripen and the largest tomatoes the shortest time.
Thus, the mean days to ripen the one lot of Rutgers tomatoes was 17 days
for the 7 x 8's and 7 x 7's; 15 days for the 6 x 7's; 13 days for the
6 x 6's; and 12 days for the 5 x 6's. With the second lot of Rutgers
tomatoes harvested one week later from the same "area, there was a marked
difference in the ripening rate of the small 7 x 8 tomatoes which averaged
only 11 days compared to 13 days for the largest tomatoes in this lot.
This difference in ripening period of 11 to 16 or 17 days for the same
sized tomatoes indicated that the first lot had a longer growing period
and probably was from different pickings or fruit hands on the plants.
It can be stated that the small 7 x 8 tomatoes are more apt to be
immature, but this is not always true.
The firmness measurements were made to check on the hypothesis that
as the tomato approaches maturity and increases in size it also tends to
become soft. Eight lots of 50 tomatoes each were obtained from Immokalee
growers. These tomatoes were Rutgers and Homestead varieties and sizes
from 7 x 8 to 6 x 6. The firmness of the various sizes as measured with
a compression-type pressure tester are shown in Table 2.
Very little difference in firmness due to size was found. This agrees
with data obtained with another type of firmness tester developed at Cornell
University by A. R. Hamson. Three lots of 7 x 7 fruit were tested and the
firmness averaged 15.0, 15.1, and 15.6 pounds. The lowest average and
maximum values were obtained with the 7 x 8 size and the highest values
with the 7 x 7 size. The firmness of the larger 6 x 7 and 6 x 6 fruit
was in between the values obtained with the two smaller sizes.
Table 2. The Relationship of Size and Firmness of Rutgers and Homestead
Variety Tomatoes at Harvest.
Size Variety Maximum Minimum Average
7 x 8 Rutgers 15.8 11.2 13.5
7 x 7 Rutgers 16.5 13.0 15.0
6 x 7 Rutgers 16.9 13.0 15.1
6 x 6 Rutgers 17.3 10.5 14.7
7 x 7 Homestead 16.9 13.6 15.1
7 x 7 Homestead 17.5 12.5 15.6
6 x 7 Homestead 16.6 13.3 15.0
6 x 6 Homestead 17.4 13.6 15.4
Firmness was measured in pounds required to compress each fruit 5/8 inch
with a pressure tester. The maximum, minimum, and average values were
obtained on 50 tomatoes of each lot obtained from commercial "green-
wrap" harvests at Immokalee.
Many attempts have been made to find suitable methods of reducing the
high costs of packing tomatoes. Substantial reduction in labor costs were
achieved by jumble packing in bulk containers compared with place packing
in lugs. However, considerable hand labor is still required for the
present jumble packing methods which often result in widely varying net
weight and fill of the containers.
Since the Agricultural Marketing Agreement Act provided authority
for regulating the pack (net weight) and containers used for marketing
tomatoes, there was a possibility for eliminating certain undesirable
practices such as excessive bulge. If mechanized packing equipment could
be used without damage to the tomatoes, there would be an opportunity for
more uniformity of pack and savings in packing cost.
Preliminary studies were made with automatic vibrating and volume-
fill equipment manufactured by the Food Machinery and Chemical Corporation.
The equipment was installed in the packing house of the Ruskin Tomato
Growers, Inc., at Ruskin, Florida. The objective of the study was to
determine the weight of the packed containers, the tomato count, the full-
ness of the containers, and the mechanical injuries of the machine packed
vs the hand packed tomatoes. The container (18 15/16 x 12 x 8) was the
No. 7007, 40 pound fiberboard, non-telescope, with divided liner. Only
one vibrating unit was available and this was located in front of the belt
delivering No.-2 grade, 6 x 6 and larger size tomatoes.
During the time the tomatoes were dropping into the box, they were
subjected to continuous vertical vibration of sufficient magnitude to
settle the fruit. When a sufficient weight of tomatoes was in the box,
it was automatically moved along the conveyor and an empty box moved into
filling position. The time required for filling varied from 50 to 65
seconds depending upon the grade and size of tomatoes being packed.
About 300 cartons were packed by the volume-fill equipment and an
equal number were packed by hand in another section of the packing house.
Both lots were loaded into the same truck for shipment to Nashville. Both
lots were Jefferson variety, but from different groups of growers.
Filled cartons were selected at random at the packing house for the
determination of fullness, weights, and tomato count. The fullness was
an average of the distances (at the four corners) between the top edge of
the carton and a flat plane across the top of the tomatoes. The results
are shown in Table 3.
The hand packed cartons averaged one pound more gross weight and a
slightly higher bulge, even though they contained fewer tomatoes than
the volume-fill cartons. The tomatoes in the hand packed cartons were
slightly larger than those in the volume-fill cartons. The small amount
of bruising found in both treatments after packing did not appear to result
from the packing operations. The amount of bruising present before packing
was not determined.
The cartons were loaded lengthwise in 6 rows across the trailer and
6 layers high with two 6-inch air channels running lengthwise from the
bunker to the rear, and extending from the floor to the top layer of
cartons. There was a 2-foot air space above the cartons. The load was
refrigerated during transit.
Ten cartons of each treatment were selected from various locations
in the load by a representative of the Federal-State Inspection Service
while the load was being unloaded in Nashville. The fill of the cartons
and the amount of bruising was determined as shown in Table 4. The fill
of the cartons varied from a slack of 2/16 inch to a bulge of 6/16 inch
in the hand packed cartons compared with a minimum slack of 1/16 inch and
a maximum bulge of 2/16 inch in the volume-fill cartons. Thus, the average
height of bulge was considerably higher in the hand packed treatment as
shown in Table 5. One-half of the volume-fill cartons sampled were level
full, while all of the hand packed cartons had either slack or bulge.
Table 3. The Effect of Volume-Fill Machinery and Hand Packing on the
Weight, Number and Bruising of Tomatoes and Fill of the Cartons
at the Packing House.
Number Cartons Measured
A. Gross Weight
B. Number Tomatoes
42 lb. 1 oz.
43 lb. 7 oz.
41 lb. 4 oz.
lb. 1 os.
lb. 6 oz.
C. Fullness of Carton
(Ave. height of bulge at
the four corners)
D. Percent Bruising
1 4/16 in.
1 8/16 "
Table 4. -
The Effect of Volume-Fill Pack vs Hand Pack of Tomato Cartons
on the Fill of the Cartons and the Bruising of the Tomatoes
After Shipment from Ruskin to Nashville by Truck.
Carton Layer in Slack* Bulge** : Percent Bruising
No. Truck Load 16's inch 16's inch : Slight Severe
Check Treatment Cartons Hand Packed
1 1 (Floor) 2.0 52 18
2 1 0.75 42 10
3 2 1.0 24 4
4 3 3.0 36 6
5 4 0.25 28 8
6 4 2.5 26 4
7 5 6.0 14 0
8 5 1.0 24 4
9 6 1.5 30 4
10 6 (Top) 4.0 6 0
---- ----- ------------------------------
Average 0.725 1.475 28.2 5.8
Treatment A Volume-Fill Cartons
1 1 (Floor) 1.25 36 6
2 2 0 0 40 10
3 3 0 0 24 8
4 4 0 0 44 6
5 4 0.5 30 6
6 5 1.0 12 4
7 5 0 0 12 2
8 6 0 0 8 2
9 6 1.0 6 0
10 6 (Top) 2.0 6 0
Average 0.225 0,350 21.8 4.4
Slack measurements are averages of the
of the carton down to the tomatoes.
four corners from the top edge
Bulge measurements are averages of the four corners from the top edge
of the carton up to the tomatoes.
Table 5. A Comparison of Container Fill and Bruising of Tomatoes Before
and After Shipping Fiberboard Cartons Packed by Hand vs Automatic
Ave. Bulge Height: Percent Bruising
16th Inch Slight Severe
Volume- Hand Volume- Hand Volume- Hand
Fill Pack Fill Pack Fill Pack
at Ruskin 18.5 20.0 2.2 0.9 1.2 0.3
to Nashville 0.1 0.8 21.8 28.2 4.4 5.8
Difference -18.4 -19.2 +19.6 +27.3 +3.2 +5.5
The inspection for injury was restricted to fresh bruising only. The
slight bruising consisted of slight pressure bruising not severe enough to
affect the grade. The severe bruising did affect grade. The slight bruising
#n the hand packed cartons ranged from 6 to 52 percent, averaging 28 per-
cent. The slight bruising in the volume-fill cartons ranged from 6 to 44
percent, averaging 22 percent. The severe bruising was also lower in the
volume-fill cartons. Bruising in both methods of packing was decidedly
worse in layers near the floor of the truck as compared with those near
the top. Since the cartons near the flor had the greatest slack and the
top cartons the greatest bulge, it was obvious that there was compression
of the fruit in the lower layers of cartons. There may be a possibility
of reducing the bruising through improvements in the cartons or loading
In order to make a further study of the possible effects of the
vibration and volume-filling procedure on the quality of the tomatoes,
six cartons of tomatoes were withheld from the commercial shipment and
observations were made on the injury, rate of ripening, and decay. As
- 10 -
shown in Table 3, the amount of bruising was slightly greater in the
volume-fill cartons than in the hand pack. However, this difference
cannot definitely be attributed to the packing procedures because the
tomatoes were from different growers and were handled differently prior
to packing. The tomatoes in the volume-fill cartons were also slightly
more mature as shown in Table 6 by the faster ripening rate.
The most significant difference which appeared during ripening was
the higher incidence of decay among the volume-fill tomatoes. After two
days at 70 F, 7.9 percent of the volume-filled lot were decayed compared
to 0.3 percent in the hand packed lot. The cause of the decay was not
definitely established although Dr. Cox of the Everglades Experiment Station
believed it to be due to mechanical injury. The decay began as a localized
soft spot of abnormal color and progressed very rapidly to liquefy the
contents of the tomato. Some of the fruit began to leak early in their
breakdown. The epidermis remained intact on others until the tomato
appeared to be a sphere of liquid. The total decay in the three cartons
of volume-filled tomatoes amounted to 11.6 percent compared with 5.2 per-
cent. Again this would have been a much better experiment if the tomatoes
could have been obtained from the same source with the same previous
It may be concluded that the volume-fill equipment showed promise
of reducing the amount of packing labor without visibly damaging the
tomatoes and further tests should be made of this equipment under better
Table 6. Rate of Ripening and Decay of Six Sample Cartons of Tomatoes Removed from the Volume-Fill
and Hand Pack Cartons Shipped to Nashville. These Tomatoes were Ripened in a Ripening
Room at the Everglades Experiment Station.
Days in Storage at 700F and 65-75% Relative Humidity
2 4 5 6 12 15 18 20
: Rate of Ripening
Volume-Fill 404 0 6.9 8.9 11.1 44.1 14.4 4.7 0.7
Hand Pack 348 0 2.3 5.2 6.6 52.6 24.1 6.0 1.7
------ -------------- ---
Decay During Ripening
% % % % % % % % Total
Volume-Fill 404 7.9 0.2 1.0 1.0 1.0 0.5 0 0 11.6
Hand Pack 348 0.3 0.3 0.6 1.1 2.0 0.6 0.3 0 5.2