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Group Title: Lake Alfred AREC research report - University of Florida Agricultural Research and Education Center ; CS-75-1
Title: Evaluation of pectinesterase activity for estimating maturity of Florida avocados
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Permanent Link: http://ufdc.ufl.edu/UF00072455/00001
 Material Information
Title: Evaluation of pectinesterase activity for estimating maturity of Florida avocados
Series Title: Lake Alfred AREC research report
Physical Description: 19 leaves : ill. ; 28 cm.
Language: English
Creator: Barmore, Charles Rice, 1942-
Rouse, A. H
Campbell, Carl W
Agricultural Research and Education Center (Lake Alfred, Fla.)
Publisher: Agricultural Research and Education Center, University of Florida, IFAS
Place of Publication: Lake Alfred FL
Publication Date: 1975
 Subjects
Subject: Avocado -- Ripening -- Florida   ( lcsh )
Avocado -- Field experiments -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by C.R. Barmore, A.H. Rouse and C.W. Campbell.
General Note: Cover title.
General Note: "March 12, 1975."
General Note: "Study supported by the Florida Avocado Administrative Committee."
 Record Information
Bibliographic ID: UF00072455
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 76804682

Table of Contents
    Title Page
        Page 1
    Acknowledgement
        Page 2
    Main
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
Full Text






(S


Agricultural Research and Education Cent

University of Flarida IA, take Alfred

u"ake Afe


EVALUATION OF PECTINESTERASE ACTIVITY FOR ESTIMATING MATURITY OF

FLORIDA AVOCADOS









by

C. R. Barmore, A. H. Rouse and C. W. Campbell










March 12, 1975

Study Supported by the Florida Avocado

Administrative Committee


Lake Alfred AREC
Research Report CS75-1
3/12/75 CRB-30









-2-























ACKNOWLEDGMENT

Acknowledgment is given to Mr. Rick Barbare for his excellent

technical assistance, to-Dr---Adair-Wheaton--for his assistance-in the

statisticaL.analysis, to the Florida Avocado Administrative Committee

(AAC) for financial support, and to the members of the Florida

avocado industry for their cooperation in supplying fruit.and--taste-

evaluation.









-3-


INTRODUCTION

This study was the first part of a proposed two-part program designed

to examine the possible use of the enzyme pectinesterase (PE) as a maturity

index for avocado fruit. Change in PE activity was measured during a nine-

week period beginning prior to the A date of commercial maturity for four

major cultivars in order to establish a PE value for each cultivar (cv.)

which could be used as an index of maturity. The second part of the study,

if approved by the Avocado Administrative Committee (AAC), would be designed

to test validity of using PE value of each cv. as an index of maturity.


FUNDING

Funding,of the study was by the AAC, the Agricultural Research and

Education Center's (AREC's) at Lake Alfred and Homestead. Itemized state-

ment of expenditures by the AAC is as follows:

1. Equipment (pH meter, controller, titrating
assembly, freezer, etc.) $1700.00

2. Technician's salary 1800.00

3. Miscellaneous 40.00

$3540.00

Additional expenditures incurred by the Centers for salaries, travel,

chemicals, etc. were approximately $2000.00

Itemized statement of time spent by Mr. Barbare on the project is as

follows: A. Harvesting fruit 46 hr

B. Tissue preparation 255 hr

C. PE analysis 225 hr

D. Ripening measurements 32 hr

E. Miscellaneous 36 hr

Total 594 hr


0











MATERIALS AND METHODS

Four major cv. were selected for the study; 'Waldin,"Booth 8,"Hall,'

and 'Lula.' Each cv. was replicated in three groves located in three

different geographical locations. Weekly sampling of each cv. four weeks

prior to the A date set by the AAC and continuing for a total of nine weeks.

At each harvest, two sets of fruit of three different size groups (small,

medium, and large), were picked from each of the three groves: one each for

PE analysis, ripening and taste evaluation. Each size group was comprised

of three to four fruit each within 75 g of the mean weight.

Procedures for tissue preparation and PE analysis were essentially the

same as those discussed in the AREC Research Report CS-74-1 (CRB) with the

exception of: (a) peeling the fruit was discontinued in the initial stages

of the study since this was found to be unnecessary, and (b) reaction time

for all analyses was ten rather than fifteen min. Both modifications were

made to reduce working time.

Procedures for evaluating ripening and quality were those used by the

AAC.


RESULTS

For reasons of clarity, results of each cv. will be discussed separately.

1. 'Waldin'

Average PE values ranged from a high of 143 to a low of 40 for the

three groves; which is desirable. Highest PE values were associated with

the initial samples as was true for all cv. sampled.

Summary of the statistical analyses of the data is as follows:

(a) Analysis of variance of PE values within (size group) and among

groves for each sampling date showed that only on one harvest








S-5-


date were the PE values within and among groves significantly

different (Table 1).

(b) Correlation analyses of PE values vs. weight at each sampling

date showed essentially no significant correlation between these

two factors (Table 2).

(c) Correlation analyses of average PE values vs. weight, diameter,

and sampling date for the combined groups and groves for the

nine weeks showed that the best correlation was between PE and

sampling date. In addition, 90% of the variation in PE activity

could be explained by variation in both sampling date and

diameter (Table 3).

(d) Correlation analyses of weight vs. taste score of each harvest

date showed no significant correlation between these two factors

(Table 2).


Based on the above statistical information, it is valid to combine the

PE values for all size groups and groves on each harvest date. In addition,

PE during the nine week period is best plotted as a function of sampling

date (Fig. 1). Taste score averages for each harvest date are also plotted.


2. 'Booth 8'

Average PE values ranged from a high of 98 to a low of 30 for the three

groves which is also desirable.

Summary of the statistical analyses of the data is as follows:

(a) Analysis of variance of PE values within (size groups) and among

groves for each sampling date showed no significant differences

among size groups for all groves, but that variation among groves

was significant on two sampling dates. However, these were in the

last three weeks of harvest (Table 4).











(b) Correlation analyses of PE values vs. weight at each sampling

date showed essentially no significant correlation between these

two factors (Table 5).

(c) Correlation analyses of the average PE values vs. weight, diameter,

and sampling date for the combined size groups and groves for the

nine weeks showed that the best correlation was between PE values

and sampling date. In addition, 79% of the variation in PE

activity could be explained by variation in sampling date (Table 6).

(d) Correlation analyses between weight and taste score at each harvest

date showed no significant correlation (Table 5).


Based on the above, it is statistically valid to combine the PE values

for all size groups and groves on each sampling date. In addition, PE

activity during the nine week period is best plotted as a function of

sampling date (Fig. 2). Taste score averages for each sampling date are

also plotted.


3. 'Hall'

Average PE values for this cv. ranged from a high of 36 to a low of 20

for the three groves. Unfortunately, fruit of this cv. were already testing

mature based on the taste evaluations made on the initial samples. Apparently,

these fruit were mature five to six weeks prior to the A date.

Summary of the statistical analyses of the data is as follows:

(a) Analysis of variance of the PE values within (size groups) and

among groves was not run since on several harvest dates fruit

were available from only two groves. However, the values did not

appear markedly different.








-7-


(b) Correlation analyses of PE values vs. weight at each sampling

date showed that only two sample dates showed significant corre-

lation between these two factors (Table 7).

(c) Correlation analyses of average PE values vs. weight, diameter,

and sampling date for the combined size groups and groves for

the nine weeks showed that the best correlation was between PE

values and sampling date (Table 8). Correlation coefficient

was much less than those for either 'Waldin' or 'Booth 8' cv.

which is probably explained by the narrow PE range. Only 38.3%

of the variation in PE activity could be explained by variation

in sampling date.

(d) Correlation analyses between weight and taste score at each

harvest date showed no significant correlation (Table 7).


Based on the above, it is statistically valid to combine the PE values for

all size groups and groves. In addition, PE activity during the nine week

period is best plotted as a function of sampling date. Taste scores for

each harvest date are also plotted.


4. 'Lula'

Average PE values for this cv. ranged from a high of 26 to a low of 20

for the three groves. The narrow range can possibly be attributed to the

fact that the fruit were testing mature one week after the sampling schedule

started. Other studies have shown higher PE values than those reported here.

Summary of the statistical analyses of the data is as follows:

(a) Analysis of variance of the PE values within (size groups) and

among groves showed that there was significant difference among

size groups on only one sampling date and on five harvest dates








-8-


among groves (Table 9). The five significant variations between

groves are probably explained by the narrow PE range.

(b) Correlation analyses of PE values vs. weight at each sampling

date showed no significant correlation between the two factors

(Table 10).

(c) Correlation analyses of average PE values vs. weight, diameter,

and sampling date for the combined size groups and groves for

the nine weeks showed that the best correlation was between PE

values and sampling date. The low correlation coefficient for

this cv. is attributed to the narrow PE range. Only 21% of the

variation in PE activity could be explained by variation in

sampling date (Table 11).

(d) Correlation analyses of weight vs. taste score also showed no

significant correlation (Table 10).


Based on the above, it is statistically valid to combine the PE values

for all size groups and groves, assuming that the low correlation between

groves is due to the narrow PE range. In addition, PE activity during the

nine week period is best plotted as a function of sampling date (Fig. 4).

Average taste scores for each harvest are also plotted.


DISCUSSION

Pectinesterase activity during the nine week period showed a marked

decline in both 'Waldin' and 'Booth 8' cv. and a slight decline in 'Hall'

and 'Lula' cv. The latter two cv. were either mature or nearly so when the

sampling program was started. Thus, representative samples of immature fruit

were not obtained from these two cv. thus accounting for the narrow PE ranges.








-9-


Statistical analyses of data for the four cv. showed no significant

differences among size groups and groves for over 90% of the sampling dates.

This suggests that the PE values can be combined irrespective of size or

grove. In addition, PE was best correlated with sampling date for all four

cv.

The general pattern of PE activity with time and the wide range in PE

activity observed with 'Waldin' and 'Booth 8' cv. suggests that PE activity

can be used as an index for estimating maturity of these two cv. Pending

sampling when these varieties are definitely immature, the narrow range for

'Lula' and 'Hall' makes it questionable for these two. However, the narrow

range does not necessarily mean that it cannot be used, pending further data.

Using the information presented in Figures 1 through 4, the following

PE values were selected to be used as an index to estimating maturity for

the four cv."

'Waldii' 80

'Booth 8' 70

'Hall' 40

'Lula' 35

These values were determined by comparing taste scores to PE values

irrespective of weight. PE values for the latter two cv. were extrapolated

from the data presented and other data independent of this study because of

the insufficient data on immature fruit.

The proposed procedure for using PE as an estimate of maturity is as

follows:

1. Procedure for selecting test groves will follow the same procedure

now used by the AAC.








. -10-


2. Time of sampling will start three to four weeks prior to the A

date set by the AAC and continue until the fruit pass maturity

based on the PE value.

3. Five fruit will be randomly selected from two trees located in

each of three groves. This will give a total of 30 fruit. The

fruit will then be randomly grouped by threes irrespective of

weight.

4. Each group will be ground together, mixed thoroughly and two 100

g samples taken for PE analysis. These samples must be frozen if

PE analysis cannot be made immediately.

5. PE analysis will be determined on each of the ten groups using the

same procedure as outlined for the present study. A reaction time

of 10 min will be used for each determination.

6. To be considered mature, seven out of ten groups must be equal to,

or less than, the assigned PE value for that cv. If cv. is

declared immature, another sample will be made seven days later.

This will continue until the fruit are declared mature.


Estimation of maturity would be based entirely on the PE value, and not

on weight as currently being done by the present method. Statistical analysis

of the data presented here indicated that there was neither correlation between

PE and weight nor between weight and taste scores. In addition, weight of a

particular fruit does not necessarily determine whether or not it is mature.

The final weight of a fruit is determined by many physiological and environ-

mental factors. Therefore, weight will only be considered, if deemed necessary,

as a means of regulating market supply. However, if it is desired to sample








S-11-


fruit on the basis of size, then the PE index would essentially replace

only the tasting procedure of the present method of estimating maturity.

Total working time for the analysis of a specific cv., picking time not

considered, would be as follows:

A. Tissue preparation 60 min

B. Tissue sampling 20 min

C. PE analysis 120 min

200 min


The time given for each step is based on modifications of the method used for

the present study.







-12-


Table 1. Analysis of variance of PE values within
(among size groups) and among groves for
each sampling date of the 'Waldin' cv.
Date F values


Significant at the 5%
Significant at the 1%
Significant at the 1%7


Size groups
.93
1.68
.63
.20
12.01*
5.03
.08
4.65
5.25


Groves
3.66
1.33
1.23
.09
3.10
2.57
4.27
6.59
24.99**


level.
level.


Table 2. Correlation analysis of PE vs. weight and
weight vs. taste score for all size groups
and groves for each sampling date of the
'Waldin' cv.
Date PE vs. weight Wt. vs. taste score

7-27 -.797
8-3 +.077 --
8-10 -.588 -.437
8-17 -.360 +.394
8-24 -.848 +.501
8-30 -.551 +.248
9-6 -.624 +.381
9-13 -.443 -.491
9-20 -.249 -.520


(1974)
7-27
8-3
8-10
8-17
8-24
8-30
9-6
9-13
9-20










Table 3. Correlation analysis of the average PE value
on each sampling date vs. weight, diameter,
and sampling date for the 'Waldin' cv.


Analys is


Coefficient


*PE vs. weight
PE vs. diameter
PE vs. sampling date


-.756
-.854
-.938


90.3% variation explained by diameter and sampling date


t t I I t


222 229


WALDEN


-------M


i


236 242 249 256 263


90
0
w

80
C)


70



60


DATE (JULIAN)


Fig. 1. Change in the average PE value of the three groves
and size groups of the 'Waldin' cv. with sampling
time.


1201-


180


40
W4


208 215


---


---------- ----------------







-14-


Table 4. Analysis of variance of PE values within (among
size groups) and among groves for each sampling
date of the 'Booth 8' cv.
Tnat F values


Size groups
.06
5.59
.85
.56
.59
1.39
.84
5.93
.74


Groves
.35
1.99
1.56
.11
5.00
.34
17.05*
11.02*
.46


Significant at the 5% level.


Table 5. Correlation analysis of PE vs. weight and
weight vs. taste score for all size groups
and groves for each sampling date of the
'Booth 8' cv.


PE vs. weight
.016
-.717
.748
-.439
-.007
.333
-.180
.221
.439


Wt vs. taste score

.588
.702


.104
.091
-.146
.051
-.309
-.002


(1974)
8-24
8-30
9-6
9-13
9-20
9-27
10-4
10-11
10-18


Date
8-24
8-30
9-6
9-13
9-20
9-27
10-4
10-11
10-18


I






-15-


Table 6. Correlation analysis of the average PE values
on each sampling date vs. weight, diameter,
and sampling date for the 'Booth 8' cv.
Analysis Coefficient
PE vs. weight -.579
PE vs. diameter -.577
PE vs. sampling date -.889
79.0% of the variation by sampling date


256 242 249 256


263 270 277 284 291


DATE (JULIAN)

Fig. 2. Change in the average PE value of the three size
groups and groves of the 'Booth 8' cv. with sampling
time.


120
e

I 80


S40


0


S.BOOTH 8
- -a




, -*--o- o-


1 1 II--


90 |
O
w
80 0
Cu,

70 -

60I-
60







-16-


Table 7. Correlation analysis of PE vs. weight and
weight vs. taste score for the combined groves
at each sampling date of the 'Hall' cv.
Date PE vs. weight Weight vs. taste score

9-20 -.74 .435
9-27 .387 .402
10-4 .023 .997
10-11 -.266 .466
10-18 .037 -.356
10-25 -.111 .276
11-1 .762 .651
11-8 -.091 .220
11-15 .996 .394


Table 8. Correlation analysis of the average PE value
on each sampling date vs. weight, diameter
and sampling date for the 'Hall' cv.

Analysis Coefficient

PE vs. weight -.012
PE vs. diameter .075
PE vs. sampling date -.618

38.3% of the variation explained by sampling date






-17-


40 HALL


30 -90
.o---o o W

20 80 M

of c
1 0 ------------------------------------------- 70 u

0 I < >-' 0 o 80 -
01 60
263 270 277 254 291 298 305 312 319
DATE (JULIAN)


Fig. 3. Change in average PE value of the three size groups
and groves of the 'Hall' cv. with sampling time.







-18-


Table 9. Analysis of variance of PE values within
(among size groups) and among groves for
each sampling date of the 'Lula' cv.
F values
Date Size groups Groves


1.07
14.21*


9-27
10-4
10-11
10-18
10-25
11-1
11-8
11-15
11-22


1.36
1.43
1.51


2.21
9.83*
3.17
8.33*
5.90
63.00**


16.00*


10.07*


Significant at 5% level.
Significant at 1% level.


Table 10.


Correlation analysis of PE vs. weight
and weight vs. taste score for all size
groups and groves combined for each
sampling date of the 'Lula' cv.


Date PE vs. weight Wt. vs. taste score

9-27 .451 .112
10-4 .147 .417
10-11 .383 -.107
10-18 .113 -.86
10-25 .712 -.128
11-1 .008 -.075
11-8 .301 .166
11-15 .014.. .178
11-22 .596 .040






-19-


Table 11.


Correlation analysis of the average PE values
on each sampling date vs. weight, diameter,
and sampling date for the 'Lula' cv.


.Analysis Coefficient
PE vs. weight -.295
PE vs. diameter -.413
PE vs. sampling date -.414
21.4% of the variation explained by diameter and
sampling date


40


30-



20-



0----------------
-0 o







0
270 277 284 291 298 305
DATE (JULIAN)


0




CO
-------- o--- 7 0 w




C)

'60
312 317 326


Fig. 4. Change in the average PE value of the three size
groups and groves of the 'Lula' cv. with sampling
time.




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