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Effect of machine stripping on the yield and grade of Brussels sprouts—II
J. ugric. Erzgng Res. (I 970) 15 ( I ) 34-38
Effect
of Machine
Stripping on the Yield and Grade of Brussels Sprouts-II
A. C. W. DAVIES*: J. A. WHEELER* One crop of Brussels sprouts was harvested and the stems were stripped by hand or in one of two machines. Buttons were graded into four sizes and the differences in yield between hand and machine stripping and between one machine and the other were compared. Loss of yield occurred when stripping with either machine, particularly where plants had been stopped. There was a significant difference in loss between machines. 1.
Introduction
In 1967-68 an experiment on the effect of machine stripping of Brussels sprouts was carried out in conjunction with the Experimental Horticultural Station at Efford. The results’ showed that losses of buttons of the 1 in and under grades occurred in early maturing varieties machine stripped before Christmas. Consequently a second experiment was conducted in the following year using one variety, Champion Packer, maturing in October and incorporating two types of mechanical strippers. The aims of the work were to assess the losses caused by the two different stripping methods, to confirm the previous results both with regard to losses and the interaction between machine stripping and stopping of plants. 2.
Techniques
The crop was direct drilled on the 9 April 1968, and the growing points of half the crop were pinched out on the 9 September 1968 (i.e. were “stopped”). Harvesting took place between the 21-24 October 1968. The stripping action of one machine (machine I) consisted of inserting the growing tip of the stem into a hole saw until 4 in had been cleared of leaf petioles and buttons, then putting the cleared portion into a second hole behind which two cage wheels pulled the rest of the stem through, forcing the buttons off against a Tufnol cone surrounding the hole. The other machine (machine 2) consisted of four knives mounted on a revolving disc and constrained towards its centre by springs. In the centre of the disc was a hole large enough to accept all sprout stems. On operating a brake the four knives opened, the disc stopped revolving and a stem could be inserted, butt end first, into the hole until two ribbed rollers gripped it. As the brake was released the knives closed around the stem and the buttons were cut off as the stem was pulled through. At harvest, equivalent numbers of stopped and unstopped stems were deleafed and cut by hand and were then brought to the packhouse in trailers. Groups of 50 stems of either type were selected at random, weighed and treated by either of the two machines, or stripped by hand. Ten groups of stopped and unstopped plants were stripped by each of the three methods making 3000 stems in all. After stripping the material from each group was passed over a roller sorting table, with the rollers spaced at b in apart, for quality inspection. The material taken off was divided into two fractions: (a) the trash and rotten sprouts; (b) the portions of stems and leaf petioles with sprouts attached (hereafter called the sprout plus stalk fraction). The good sprouts passed to a diverging belt size grader and were collected in the following size ranges <$ in, $1 in, l-l 4 in, 1 h-2 in. The weight of the sprouts in each grade, the rotten buttons, trash, and the sprout plus stalk fraction were all determined. The latter fraction was then hand stripped and the sprouts graded and weighed as above. The material from the pre-stripping hole saw treatment of the machine 1 was also graded and weighed. In the particular crop used it was found that the butt ends of the stems had to be pre-stripped for smooth operation of machine 2 and the buttons removed were passed directly into the grading line and treated as part of the sample. *Members
of Harvesting
& Conservation
Department,
N.I.A.E.
34
\. C. W.
DAVIES;
35
J. A. WHEELER
3.
Results
Yields given are expressed as a % of the original sample weight and analyses made of classified material from the six field treatments, the four separate grades, where applicable, and the total combined weights of all grades. The material was categorized into the following five classes:(1) The yield of the first bulk of sprouts as received from the size grader, without from the hole saw treatment or those from the sprout plus stalk fraction; (2) the total marketable yield of sprouts obtained from all fractions; (3) the yield of sprouts from the stalk plus sprout fraction; (4) the total weight of the sprout plus stalk fraction; (5) the total amount of trash and rotten sprouts received from all sources.
the sprouts
The above will he referred to hereafter as classes l-5 respectively. Class I was based on the practice of commercial holdings observed over the seasons 1967-69 where no recovery from the various fractions was noted, and class 2 was the total marketable yield of sprouts available after machine stripping, i.e. all good sprouts, other than those destroyed by the machine treatment. Tables IA and B give the results of the analyses of classes 1 and 2 respectively. These show that with stopped plants a considerable loss in yield in the three smaller grades took place with both types of strippers. In overall yield the losses were nearly 22 % and 26 % with the machines 1 and 2 respectively, machine 1 giving a greater loss in the <$ in grade. With unstopped plants the losses were a little smaller, though still highly significant, particularly in the 2-l in grade. The overall losses were lower by nearly 7 % and 4 % with machines 1 and 2 respectively. Between the two machines, No. 2 gave a higher yield in the smallest grade. With the total marketable yield, in stopped plants (Table IB) the losses were reduced, as a considerable amount of material was recovered by further handwork on the machine stripped samples. Serious losses occurred with machine No. 1 in the two smaller grades with an overall loss of 6.5 “/,. Comparing the two types of machine, significant differences were measured in the two smaller grades and in total overall yield, where machine 2 proved the better. With unstopped plants machine 1 gave a low yield in the <$ in grade and machine 2 gave an increased yield in the 2-l in grade compared with the hand control. Comparing stopped and unstopped plants, in the hand stripping group stopping gave a significantly increased yield in the i-1 in grade of 1.9%. Between machine treatments of unstopped plants, the cutting type gave a significant increase of yield of 0.3 % in the <$ in grade for class 2 and in class 1 machine No. 1 gave a higher overall yield of 2.1 yd which was significant at the 5 5,; level. In all other comparisons there was no difference between the two groups of plants. The analyses of classes 3 and 4, Table II, showed that machine 2 gave a significantly greater yield of material at the 1% level in all the size grades and in the total amount of the sprout plus stalk fraction. There was little difference between the stopped and unstopped plants. The analysis of class 5 showed that the stopped plants stripped by machine I gave a 2.47;; greater amount of trash, significant at the 1 % level, compared to the other treatments, but in the unstopped plants there were no differences at all. 4.
Discussion
The results confirmed those given previously’ that machine stripping lowered the yield of sprouts, particularly in the smaller grades, and also that machine stripping eliminated any increase of yield given by stopping plants. In this second experiment distinctions were made between what appears to be normal commercial practice, class 1, and the total yield of sprouts remaining after machine stripping, class 2. In class 1 the differences between the two stripping machines was apparent in the <$ in grade where the cutting type did less damage, which would be expected, as the pre-stripping treatment of machine 1 is damaging to the top of the plant. The figures for the g-1 in grade were similar but the advantage of machine 1 in the larger two
I loss in wt of machine
stripped
Brussels
sprouts
2
2
Stopped Hand-Machine I Hand-Machine 2 Machine I-Machine
Unsfopprd Hand-Machine I Hand-Machine 2 Machine I-Machine
OrI
0.55” 0.29 N.S. __0.84***
0.51** -0.04 H.S. -0.55***
I ~0.34**
0.96”. 0.62”
1.028’ 0.72** -0.30***
_____
Difler,
35.7 -18.8 84.8
33.6 ~ 2.6 -54.5
62.3 40.3 ~ 37.0
- 37.5
67.1 47.4
0.3 I m~O.18 -0.49
0.29 0.01 -0.28
-0.16
0.59 0.53 N.S.
0.50 N.S. 1.42” ~ I.9211
2.11’8 0.25 N.S. ~ 1.86**
3.15*** 2.93*** @22 N.S.
~0.15
5.191” 5.04.‘.
~
-_-
4.5 12.7 IS.00
16.1 I.9 16.9
28.2 26.2 2.7
39.6 38.5 1.9
*Indicates
0.44 _~0.90 I.34
I.41 0.38 ~ I.03
I .82 I .57 0.25
3.11 3.04 0.07
2
N.S. N.S. N.S.
significance
0.11 0.53 0.42
@64 N.S. -1.17 N.S. ~ I.81 N.S.
B-Clnss
2.74* 6.19*** 3.45’
3.90** 5.95*** 2.05 N.S.
level
I
2.2 4.1 -6.4
9-4 21.2 13.0
13.6 20.7 8.2
0.89 0.01 ~--@88
2.69 3.85 I.16
-0.15 -0.35 -0.20
0.39 0.31 0.70
0.22 0.56 0.34
N.S. N.S. N.S.
N.S. N.S. N.S.
N.S. N.S. N.S.
10.0 7.9 16.3
3.5 ~-8.12 - 4.5
-
5.0 13.1 8.4
‘,, Loss
actual
TABLE “6 loss of grade.
Comparison
wt,
.-2 in
in O& of sample
Grade
Stopped Hand-Machine I Hand-Machine 2 Machine I-Machine 2 ---__Unstopped Hand-Machine I Hand-Machine 2 Machine l&Machine 2
____-_
____
Difference
-
@OO 0.02
0.19 0.15 0.34
0.20 0.39 0.19
dig?. kg
Acruol
~
3.11** I.31 N.S.
6.46*** 10.05** 3.59 N.S.
10.33*** l2.27** I.94 N.S.
6-5 2.7
14.1 21.9 9.1
21.7 25.7 52
2.59 0.42
I.46
3.88 5.34
6-59 7-71 I.12
4.
C
W.
DAVIES;
J. A.
37
WHEELER TABLE II
Difference in ‘:,>sampleweights, for
sproutsfrom Sproutand I>,,
totalsample wt ofsprouts from sprout +stalk (Class
_____1 in
C;rCld:,
talk fraction and total wt of fraction.
$-I
in
3) ~__ in 11-2
I&l&
fraction
~in
Total yield fraction. kg
Stopped
machine 2I diff. a0 machine 2%machine I)
I
I actual I’<)increase wt increase of grade machine 2-machine I
0.18 0.76 0.58’.
diff. “& (machine 2-machine machine 2-machine
I
Total weight and stalk frarrim (Clm 4)
2.46 7.12 4.66’;
0.90 0.40 0.50 N.S.
-
13.57 4.43 9.14”
206.24 IO I3-86**
76.3 0.35
71.0 I .88
65.4 2.58
55.6 0.29
67. 5.10 I
69.00 7-61
81.3 0.91 0.17 0.45
66. 416 I.60 I.41 I
64.1 5.66 2.10 2-03
51.6 0.64 0.71I 0.3
65.5 4.36 3.92 11.37
70.00 17~40 7.00 5.22
kg
machine actual “,, increase wt2Iincrease of grade
Llnstopped
4.79 I.39 3.40**
sprout -~..-~~~
-__-____ i
Classes 3 and 4
0.74”
I)
2.75**
3.63”
0.33”
7.45**
12.18”
kg I
I
I
*Indicates significance
level
grades was due to the greater amount of sprout plus stalk fraction from machine 2 and this gave the latter a poorer overall performance. In no comparison was any significant loss noted in the largest grade. Overall losses in the unstopped group of plants were 4-7 ?d less than in the stopped plants blut generally the figures followed the same pattern. The difference of losses between hand and machine stripping was greatly reduced in class 2 compared to class 1. This reduction was caused in machine 2 by recovery of sprouts from the sprout plus stalk fraction and in the other machine from both this and the pre-stripping fraction. The recovery of buttons from all fractions eliminated losses from machine 2 but such recovery still gave significant losses in the two small grades and overall yield for machine 1, which indicated that there was more positive destruction of buttons with this machine. In the unstopped plants the same pattern of figures was obtained except that there was a significantly greater recovery of material in the it-1 in grade from the cutting treatment of machine 2 than there was from the hand stripped controls. There is no obvious explanation for this, particularly as it did not occur in the stopped plants. The increase in the stalk and sprout fraction from machine 2 treatment was due to two factors:(a) an appreciable number of stems broke in the machine and the tops came through to the sorting table and (b) the abscission layers of the buttons were situated outside the basic circumference of the stem and the knives of the stripper tended to slice below the abscission layer thus leaving portions of stem attached to the buttons. The second of the above factors is basically varietal and the first probably a mixture of variety, culture and maturity. The cutting machine can be fitted with differing types of knives which may reduce the sprout plus stalk fraction. The two main economic effects of the above losses are: (a), that the vast bulk of the losses occur in the < 14 in grades which constitute the range used for freezing, and (b) the losses, coupled with the requirement for a full inspection line when mechanical stripping is employed. cause the increased harvesting costs compared to the traditional hand picking m%hods._
(a) (b) (c)
(d) (e)
5. Conclusions Using what appears to be normal commercial practice. in one variety, Champion Packer, there are considerable losses of brussels sprouts when machine stripping is employed. Machine los,ses are greater in the smaller grades of sprouts. There is less destruction of buttons with the machine employing the cutting mechanism than there is with the machine that forces the buttons off, but when commercial practice was employed the latter type gave a higher yield. Losses from stopped plants were higher than those from unstopped plants. The previous result, that machine stripping reduced the extra yield normally obtained by stopping., was confirmed.
38
EFFECT
OF MACHINE
STRIPPING
ON
BRUSSELS
SPROU
IS
Acknowledgements The authors wish to thank the Director and staff at Efford Experimental Station for theil help, to D. M. J. Higgs of the N.I.A.E. who carried out the statistical analysis, and to Messrs Horti-Tools Ltd and Lockwood Graders Ltd for loan of equipment.
REFERENCE ’
Davies, A. C. W.; Wheeler, J. A. Eflect of machine stripping on the yield andgrade qf Brussels sprouts. J. agric. Engng Res, 1968, 13 (3) 241
Effect
of Machine
Stripping on the Yield and Grade of Brussels Sprouts-II
A. C. W. DAVIES*: J. A. WHEELER* One crop of Brussels sprouts was harvested and the stems were stripped by hand or in one of two machines. Buttons were graded into four sizes and the differences in yield between hand and machine stripping and between one machine and the other were compared. Loss of yield occurred when stripping with either machine, particularly where plants had been stopped. There was a significant difference in loss between machines. 1.
Introduction
In 1967-68 an experiment on the effect of machine stripping of Brussels sprouts was carried out in conjunction with the Experimental Horticultural Station at Efford. The results’ showed that losses of buttons of the 1 in and under grades occurred in early maturing varieties machine stripped before Christmas. Consequently a second experiment was conducted in the following year using one variety, Champion Packer, maturing in October and incorporating two types of mechanical strippers. The aims of the work were to assess the losses caused by the two different stripping methods, to confirm the previous results both with regard to losses and the interaction between machine stripping and stopping of plants. 2.
Techniques
The crop was direct drilled on the 9 April 1968, and the growing points of half the crop were pinched out on the 9 September 1968 (i.e. were “stopped”). Harvesting took place between the 21-24 October 1968. The stripping action of one machine (machine I) consisted of inserting the growing tip of the stem into a hole saw until 4 in had been cleared of leaf petioles and buttons, then putting the cleared portion into a second hole behind which two cage wheels pulled the rest of the stem through, forcing the buttons off against a Tufnol cone surrounding the hole. The other machine (machine 2) consisted of four knives mounted on a revolving disc and constrained towards its centre by springs. In the centre of the disc was a hole large enough to accept all sprout stems. On operating a brake the four knives opened, the disc stopped revolving and a stem could be inserted, butt end first, into the hole until two ribbed rollers gripped it. As the brake was released the knives closed around the stem and the buttons were cut off as the stem was pulled through. At harvest, equivalent numbers of stopped and unstopped stems were deleafed and cut by hand and were then brought to the packhouse in trailers. Groups of 50 stems of either type were selected at random, weighed and treated by either of the two machines, or stripped by hand. Ten groups of stopped and unstopped plants were stripped by each of the three methods making 3000 stems in all. After stripping the material from each group was passed over a roller sorting table, with the rollers spaced at b in apart, for quality inspection. The material taken off was divided into two fractions: (a) the trash and rotten sprouts; (b) the portions of stems and leaf petioles with sprouts attached (hereafter called the sprout plus stalk fraction). The good sprouts passed to a diverging belt size grader and were collected in the following size ranges <$ in, $1 in, l-l 4 in, 1 h-2 in. The weight of the sprouts in each grade, the rotten buttons, trash, and the sprout plus stalk fraction were all determined. The latter fraction was then hand stripped and the sprouts graded and weighed as above. The material from the pre-stripping hole saw treatment of the machine 1 was also graded and weighed. In the particular crop used it was found that the butt ends of the stems had to be pre-stripped for smooth operation of machine 2 and the buttons removed were passed directly into the grading line and treated as part of the sample. *Members
of Harvesting
& Conservation
Department,
N.I.A.E.
34
\. C. W.
DAVIES;
35
J. A. WHEELER
3.
Results
Yields given are expressed as a % of the original sample weight and analyses made of classified material from the six field treatments, the four separate grades, where applicable, and the total combined weights of all grades. The material was categorized into the following five classes:(1) The yield of the first bulk of sprouts as received from the size grader, without from the hole saw treatment or those from the sprout plus stalk fraction; (2) the total marketable yield of sprouts obtained from all fractions; (3) the yield of sprouts from the stalk plus sprout fraction; (4) the total weight of the sprout plus stalk fraction; (5) the total amount of trash and rotten sprouts received from all sources.
the sprouts
The above will he referred to hereafter as classes l-5 respectively. Class I was based on the practice of commercial holdings observed over the seasons 1967-69 where no recovery from the various fractions was noted, and class 2 was the total marketable yield of sprouts available after machine stripping, i.e. all good sprouts, other than those destroyed by the machine treatment. Tables IA and B give the results of the analyses of classes 1 and 2 respectively. These show that with stopped plants a considerable loss in yield in the three smaller grades took place with both types of strippers. In overall yield the losses were nearly 22 % and 26 % with the machines 1 and 2 respectively, machine 1 giving a greater loss in the <$ in grade. With unstopped plants the losses were a little smaller, though still highly significant, particularly in the 2-l in grade. The overall losses were lower by nearly 7 % and 4 % with machines 1 and 2 respectively. Between the two machines, No. 2 gave a higher yield in the smallest grade. With the total marketable yield, in stopped plants (Table IB) the losses were reduced, as a considerable amount of material was recovered by further handwork on the machine stripped samples. Serious losses occurred with machine No. 1 in the two smaller grades with an overall loss of 6.5 “/,. Comparing the two types of machine, significant differences were measured in the two smaller grades and in total overall yield, where machine 2 proved the better. With unstopped plants machine 1 gave a low yield in the <$ in grade and machine 2 gave an increased yield in the 2-l in grade compared with the hand control. Comparing stopped and unstopped plants, in the hand stripping group stopping gave a significantly increased yield in the i-1 in grade of 1.9%. Between machine treatments of unstopped plants, the cutting type gave a significant increase of yield of 0.3 % in the <$ in grade for class 2 and in class 1 machine No. 1 gave a higher overall yield of 2.1 yd which was significant at the 5 5,; level. In all other comparisons there was no difference between the two groups of plants. The analyses of classes 3 and 4, Table II, showed that machine 2 gave a significantly greater yield of material at the 1% level in all the size grades and in the total amount of the sprout plus stalk fraction. There was little difference between the stopped and unstopped plants. The analysis of class 5 showed that the stopped plants stripped by machine I gave a 2.47;; greater amount of trash, significant at the 1 % level, compared to the other treatments, but in the unstopped plants there were no differences at all. 4.
Discussion
The results confirmed those given previously’ that machine stripping lowered the yield of sprouts, particularly in the smaller grades, and also that machine stripping eliminated any increase of yield given by stopping plants. In this second experiment distinctions were made between what appears to be normal commercial practice, class 1, and the total yield of sprouts remaining after machine stripping, class 2. In class 1 the differences between the two stripping machines was apparent in the <$ in grade where the cutting type did less damage, which would be expected, as the pre-stripping treatment of machine 1 is damaging to the top of the plant. The figures for the g-1 in grade were similar but the advantage of machine 1 in the larger two
I loss in wt of machine
stripped
Brussels
sprouts
2
2
Stopped Hand-Machine I Hand-Machine 2 Machine I-Machine
Unsfopprd Hand-Machine I Hand-Machine 2 Machine I-Machine
OrI
0.55” 0.29 N.S. __0.84***
0.51** -0.04 H.S. -0.55***
I ~0.34**
0.96”. 0.62”
1.028’ 0.72** -0.30***
_____
Difler,
35.7 -18.8 84.8
33.6 ~ 2.6 -54.5
62.3 40.3 ~ 37.0
- 37.5
67.1 47.4
0.3 I m~O.18 -0.49
0.29 0.01 -0.28
-0.16
0.59 0.53 N.S.
0.50 N.S. 1.42” ~ I.9211
2.11’8 0.25 N.S. ~ 1.86**
3.15*** 2.93*** @22 N.S.
~0.15
5.191” 5.04.‘.
~
-_-
4.5 12.7 IS.00
16.1 I.9 16.9
28.2 26.2 2.7
39.6 38.5 1.9
*Indicates
0.44 _~0.90 I.34
I.41 0.38 ~ I.03
I .82 I .57 0.25
3.11 3.04 0.07
2
N.S. N.S. N.S.
significance
0.11 0.53 0.42
@64 N.S. -1.17 N.S. ~ I.81 N.S.
B-Clnss
2.74* 6.19*** 3.45’
3.90** 5.95*** 2.05 N.S.
level
I
2.2 4.1 -6.4
9-4 21.2 13.0
13.6 20.7 8.2
0.89 0.01 ~--@88
2.69 3.85 I.16
-0.15 -0.35 -0.20
0.39 0.31 0.70
0.22 0.56 0.34
N.S. N.S. N.S.
N.S. N.S. N.S.
N.S. N.S. N.S.
10.0 7.9 16.3
3.5 ~-8.12 - 4.5
-
5.0 13.1 8.4
‘,, Loss
actual
TABLE “6 loss of grade.
Comparison
wt,
.-2 in
in O& of sample
Grade
Stopped Hand-Machine I Hand-Machine 2 Machine I-Machine 2 ---__Unstopped Hand-Machine I Hand-Machine 2 Machine l&Machine 2
____-_
____
Difference
-
@OO 0.02
0.19 0.15 0.34
0.20 0.39 0.19
dig?. kg
Acruol
~
3.11** I.31 N.S.
6.46*** 10.05** 3.59 N.S.
10.33*** l2.27** I.94 N.S.
6-5 2.7
14.1 21.9 9.1
21.7 25.7 52
2.59 0.42
I.46
3.88 5.34
6-59 7-71 I.12
4.
C
W.
DAVIES;
J. A.
37
WHEELER TABLE II
Difference in ‘:,>sampleweights, for
sproutsfrom Sproutand I>,,
totalsample wt ofsprouts from sprout +stalk (Class
_____1 in
C;rCld:,
talk fraction and total wt of fraction.
$-I
in
3) ~__ in 11-2
I&l&
fraction
~in
Total yield fraction. kg
Stopped
machine 2I diff. a0 machine 2%machine I)
I
I actual I’<)increase wt increase of grade machine 2-machine I
0.18 0.76 0.58’.
diff. “& (machine 2-machine machine 2-machine
I
Total weight and stalk frarrim (Clm 4)
2.46 7.12 4.66’;
0.90 0.40 0.50 N.S.
-
13.57 4.43 9.14”
206.24 IO I3-86**
76.3 0.35
71.0 I .88
65.4 2.58
55.6 0.29
67. 5.10 I
69.00 7-61
81.3 0.91 0.17 0.45
66. 416 I.60 I.41 I
64.1 5.66 2.10 2-03
51.6 0.64 0.71I 0.3
65.5 4.36 3.92 11.37
70.00 17~40 7.00 5.22
kg
machine actual “,, increase wt2Iincrease of grade
Llnstopped
4.79 I.39 3.40**
sprout -~..-~~~
-__-____ i
Classes 3 and 4
0.74”
I)
2.75**
3.63”
0.33”
7.45**
12.18”
kg I
I
I
*Indicates significance
level
grades was due to the greater amount of sprout plus stalk fraction from machine 2 and this gave the latter a poorer overall performance. In no comparison was any significant loss noted in the largest grade. Overall losses in the unstopped group of plants were 4-7 ?d less than in the stopped plants blut generally the figures followed the same pattern. The difference of losses between hand and machine stripping was greatly reduced in class 2 compared to class 1. This reduction was caused in machine 2 by recovery of sprouts from the sprout plus stalk fraction and in the other machine from both this and the pre-stripping fraction. The recovery of buttons from all fractions eliminated losses from machine 2 but such recovery still gave significant losses in the two small grades and overall yield for machine 1, which indicated that there was more positive destruction of buttons with this machine. In the unstopped plants the same pattern of figures was obtained except that there was a significantly greater recovery of material in the it-1 in grade from the cutting treatment of machine 2 than there was from the hand stripped controls. There is no obvious explanation for this, particularly as it did not occur in the stopped plants. The increase in the stalk and sprout fraction from machine 2 treatment was due to two factors:(a) an appreciable number of stems broke in the machine and the tops came through to the sorting table and (b) the abscission layers of the buttons were situated outside the basic circumference of the stem and the knives of the stripper tended to slice below the abscission layer thus leaving portions of stem attached to the buttons. The second of the above factors is basically varietal and the first probably a mixture of variety, culture and maturity. The cutting machine can be fitted with differing types of knives which may reduce the sprout plus stalk fraction. The two main economic effects of the above losses are: (a), that the vast bulk of the losses occur in the < 14 in grades which constitute the range used for freezing, and (b) the losses, coupled with the requirement for a full inspection line when mechanical stripping is employed. cause the increased harvesting costs compared to the traditional hand picking m%hods._
(a) (b) (c)
(d) (e)
5. Conclusions Using what appears to be normal commercial practice. in one variety, Champion Packer, there are considerable losses of brussels sprouts when machine stripping is employed. Machine los,ses are greater in the smaller grades of sprouts. There is less destruction of buttons with the machine employing the cutting mechanism than there is with the machine that forces the buttons off, but when commercial practice was employed the latter type gave a higher yield. Losses from stopped plants were higher than those from unstopped plants. The previous result, that machine stripping reduced the extra yield normally obtained by stopping., was confirmed.
38
EFFECT
OF MACHINE
STRIPPING
ON
BRUSSELS
SPROU
IS
Acknowledgements The authors wish to thank the Director and staff at Efford Experimental Station for theil help, to D. M. J. Higgs of the N.I.A.E. who carried out the statistical analysis, and to Messrs Horti-Tools Ltd and Lockwood Graders Ltd for loan of equipment.
REFERENCE ’
Davies, A. C. W.; Wheeler, J. A. Eflect of machine stripping on the yield andgrade qf Brussels sprouts. J. agric. Engng Res, 1968, 13 (3) 241