POSTHARVEST SENSORY AND PHYSIOCHEMICAL ATTRIBUTES OF PROCESSING AND NONPROCESSING TOMATO CULTIVARS

POSTHARVEST SENSORY AND PHYSIOCHEMICAL ATTRIBUTES OF PROCESSING AND NONPROCESSING

TOMATO CULTIVARS

MAJEED MOHAMMED', LAWRENCE A. WILSON and PATRICK I. GOMES

Department of Food Production Faculty of Agriculture and Natural Sciences

The University of the West Indies St. Augustine Trinidad, W.I.

Accepted for Publication March 25, 1998

ABSTRACT

Fruits of processing and nonprocessing tomato cultivars harvested at the "breaker"stage of maturity were evaluated for changes in physical, chemical and sensory quality characteristics during storage at 20C and 30C after 7, 14 and 21 days. Percentage marketablefiits after 21 days at 20C and 30C were 61.9% and 56.6% for processing cultivars and 65.9% and 50.9% for nonprocessing cultivars. Fruits of the processing cultivars ripened earlier, remained firmer and were less prone to physical injuries than fruits of nonprocessing cultivars. Nonprocessing fruits had a higher mean fmi t weight of 17.0 g, @it diameter of 1.10 mm and Iocule number of 1.3 compared withfnrits of the processing cultivars. Nonprocess- ingfruit cultivars had higher sugar/acid ratios and vitamin C contents as well as lower pH and total titratable acidity than processingfiit cultivars. Accordingly, nonprocessing cultivars on the whole, but specif;cally Walters. Floradel, Carnival, Calypso, Star Pak, Floradade and Early Set were most suitable as fresh-market

fnrits. Excellent processing quality attributes were obtained for Donore. Pet0 94C. Rio Grande and Advantage. Among processing cultivars Caraibe. Cascade, Dorado and Neema 1401 gave good dual purpose fruits.

INTRODUCTION

In the Caribbean, fruits of processing tomato cultivars have dominated the fresh fruit market over nonprocessing cultivars within recent years. The change to processing cultivars evolved from an apparent contradiction in the perceived definition of tomato quality characteristics between wholesaler, producer and

'To whom to correspond with.

Journal of Food Quality 22 (1999) 167-182. All Rights Reserved. "Copyright 1999 by Food & Nutrition Press. Inc.. Trumbull. Connecticut. 167

168 M. MOHAMMED, L.A. WILSON and P.I. GOMES

consumer (Mohammed 1992). Wholesalers on the one hand have demanded cultivars that can withstand abusive handling, in which fruits are subjected to less than ideal environmental conditions. Producers have focused on high yields, good keeping quality and uniform ripening patterns (Mohammed 1992). However, although consumers have indicated preference for a fresh or table tomato, throughout the year, at an affordable price with optimum color, slicing quality, taste and flavor (Mohammed 1992), in the final analysis they have been forced to accept processing tomato cultivars chosen on the basis of quality perceptions best suited to wholesalers or producers.

Whde production and post-production characteristics of some nonprocessing cultivars have been extensively tested previously (Hicks et al. 1975; Yang et al. 1987; Shewfelt et al. 1988; Gull et al. 1989; Jackman et al. 1990), comparative evaluations of postharvest quality in processing and nonprocessing genotypes produced and traded in the Caribbean have not been reported. Such information would be vital for the tomato industry since it would identify cultivars best suited for fresh use, or processing purposes (ketchups, pastes and juices) versus dual purpose cultivars (both fresh and processing) and so help in clarifying some of the perceived differences in tomato quality requirements that exist between producers, traders arid consumers.

The objective of this study was aimed at evaluating the physical, chemical and sensory quality changes during storage of 16 popular processing and nonprocessing tomato cultivars.

MATERIALS AND METHODS

The investigations were carried out on eight processing and eight nonprocessing tomato cultivars grown at the University of the West Indies Field Station, Valsayn, Trinidad. The processing cultivars were Dorado, Advantage, Pet0 94C, Neema 1401, Caraibe, Rio Grande, Donore and Cascade. The nonprocessing cultivars were Calypso, Floradade, Floradel, Early Set, Star Pak, Carnival, Walters and Capitan. The fruits were harvested by hand at “breaker stage” as described by Kader and Moms ( 1976) and Dodds and Ludford (1 990). A few hours after their anival at the laboratory the h i t s were carehlly selected, washed, dipped for three minutes in a 300-ppm chlorine solution, dned, numbered and individually weighed. Ninety fruits from each cultivar at the same stage of maturity, of uniform sue and color in a completely randomized design were placed in separate cardboard cartoons, divided into three replicates consisting of thirty fruits per replicate and stored in separate room at 20 and 30C and 70 - 75% r.h. for 7, 14, and 21 days, respectively. At the end of each storage interval at both temperatures, data on samples of five fruits per cultivar replicated three times were taken individually for the following: (1) Physical measurements such as average fiuit weight (g), number

POSTHARVEST QUALITY ATTRIBUTES OF TOMATO 169

of locules, firmness, pericarp thickness (mm) and fruit diameter (mm). Pericarp thickness and fruit diameter were measured with a Vernier caliper (Manostat, Fisher Scientific, Springfield N.J.). (2) Chemical analyses: pH, total soluble solids (TTS), total titratable acidity (TTA), sugar acid ratio (TSS:ITA), ascorbic acid content, similar to methods described by Kader et al. (1977). (3) Other parameters of marketability, such as percentage marketable h i t s , color development, sensory evaluations, puffiness, total solids and total pectin.

Marketable quality was evaluated according to the scoring method used by Sherman and Allen (1983) based on a 1-9 rating with 1 = unusable; 3 = unsalable; 5 = fair; 7 = good; and 9 = excellent. The number of fruits receiving a rating of 5 and above was used to calculate the percentage marketable fruits. Color was measured (mean of 8 circumferential measurements using a pink standard: L= 69.1, a=+23.4, b= +9.3) with a Gardner XL Colorimeter (Gardner Pacific Scientific Co., Silver Springs, MD 20910). Readings for hue (tan-' b/a), value (L) and chroma (a' + b2) Y2 were converted to a tomato color index as determined by Hobson (1987) using equation, 2000 + Lda2 + b2 (Hobson et al. 1983).

Sensory evaluation for flavor, texture, appearance and overall acceptability was based on ratings used by Kearney and Coffey (1 983). A panel consisting of 22 observers at each of the sessions rated quarter sections twice on a hedonic scale of 1 - 6. Flavor scale was from 1 = very sweet to 6 = very acid. Texture scale was from 1 = very smooth to 6 = very mealy. Appearance scale was from 1 = excellent to 6 = very poor. Overall acceptability ranged from 1 = like very much to 6 =

disldce very much. Puffiness resulting from poor development of the locule tissue and excess

extension of the pericarp was rated according to the method used by Asahira and Hosolu (1977). Degree of puffiness was rated fiom 1 to 5 with 1 = none (excellent slicing quality), 2 = slight, small voids in one or two locules, 3 = moderate, small voids in more than two locules, 4 = severe, medium to large voids in most or all locules and 5 = extreme, large voids in all locules.

To determine total solids, duplicate 25 g samples were weighed on aluminum foil, transferred to Petri dishes and dried at 5OC in a Gallenkamp oven for 24 h (Wahem 1988). Total pectins (mg/lOOg) were determined according to the method of Kertesz (195 1).

RESULTS

Physical Analysis

Apart from pericarp thickness, measurements of mean fruit weight, fruit diameter and locule number were higher for nonprocessing compared with processing cultivars (data not shown).


Average fruit weight (58-68g per fruit) and h i t diameter (5.8 - 6.3 mm per fruit) were highest for nonprocessing cultivars Floradel, Star Pak and Carnival. The lower extremities of these two physical parameters were obtained for seventy-five percent of the processing cultivars inclusive of Donore, Cascade, Advantage, Pet0 94C, Dorado and Rio Grande. These cultivars had mean fruit weights and fruit diameters ranging at 25 - 35g per fruit and 4.0 - 4.5mm per fruit, respectively. Neema 140 1 and Caraibe comprised the other two processing cultivars with slightly higher fruit weights (36-468 and 47 - 57g per fruit, respectively) and fruit diameters (4.6 -5.lmm and 5.2 - 5.7 mm per fruit, respectively). While locule number averaged 2.0 - 3.0 for processing cultivars, all the nonprocessing cultivars were in excess of 3.5 - 5.2 except for Carnival and Walters which were grouped in the highest range of 5.3 - 6.3 (data not shown).

Percentage Marketable Fruits

All processing cultivars had 100% marketable fruits after 7 days at 20C and 30C (Table l), excepting Donore which showed a 20% reduction at 30C (Table 1). Three processing cultivars, Dorado, Advantage and Caraibe stored at 20C, continued to have 100% marketable fruits after 14 days. Only Advantage maintained this trend after 14 days at 30C (Table 1). After 21 days at 20C Cascade and Advantage had the highest percentage marketable fruits. For the same duration at 30C Cascade accounted for the highest percentage marketable fruits followed by Donore, Rio Grande and Advantage.

Nonprocessing cultivars, Floradade, Early Set, Star Pak and Carnival had 100% marketable fruits after seven days at 20C and 30C, respectively. Of these four cultivars, only Floradade continued h s trend for an additional seven days at both temperatures (Table 1). However, after 21 days at 20C Floradade was reduced to only 53.7% marketable fruits compared with 76.7% for Early Set. Floradel showed the highest percentage of marketable fruits after 2 1 days at 20C or 30C.

Carnival which was 100% marketable after seven days at 30C declined by 57.1% after 14 days and a further 19.5% after 21 days at the same temperature (Table 1). Early Set which also showed 100% marketable fruits after 7 days at 30C declined by 23.2% and 50.0% after 14 days and 21 days respectively at the same temperature (Table 1).

Color Development

Fruit with similar color measurements were grouped together and separated into processing and nonprocessing cultivars (Table 2). All tomato cultivars except Capitan had a more uniform and intense red color after 14 days at both temperatures compared with the same cultivars evaluated 7 days earlier (Table 2).

POSTHARVEST QUALITY AlTRIBUTES OF TOMATO 171

Capitan, a nonprocessing cultivar ripened with a pale yellow color throughout storage at both temperatures (Table 2).

TABLE 1. PERCENTAGE MARKETABLE FRUITS OF DIFFERENT TOMATO

CULTNARS AFTER 7,14 AND 21 DAYS AT 20C AND 30C RESPECTIVELY

Tomato Cultvars

Processing Dorado Advantage Peto 94C Neema 1401 Caraibe Rio Grande Donore Cascade

Non-processing C a I y p s o Floradel Floradade Early set Star Pak Carnival W&WS Capitan LSD (0.05)

100.0'b 100.0b 100.0b 100.0b 100.0b 100.0b 100.0b 100.0b

100.0b 100.0b 100.0b 100.0b 100.0b 100.0b 8O.Oa 100.0b

90.0ab 90.0ab 90.0ab 90.0ab 100.0b 100.0b 100.0b 100.0b 100.0b 100.0b 100.0b 100.0b 90.0ab 90.0ab 80.0a 85.0a

12.8

1OO.W 100.0d 8 7 . M 66.6bc 100.W 88.9cd 7 6 . M 9O.M

77.7cd 100.0d 62.5bc 55.5a 77.7cd 66.7bc 70.0bc 88.9cd

77.acd 75.7cd 9o.ocd 81.Ocd 100.0d 100.0d 77.8cd 76.8cd 77.8cd 70.0bc 66.7bc 42.9a 62.5bc 53.3a 60.0b 55.6a

1s 7

64.3cde 70.6cdef 65.9cdef

41 .Ob 48.6bc

68.4cdef 65.2cdef 71.4cdef

53.3bc 61.lcd 46.4bc 46 4bc 44.lbc 63.6cde 65.9cdef 72.0cdef

66.7cdef 60.9cd

53.8bc 45.8bc 76.7efg 50.0bc 74.4cdef 59.4~ 63.2cde 23.4a 57 .9~ 46.7bc 51.7bc 42.7b

14 3

a3.a 7a.srg

Mean of 5 fruits/treatment x 3 replicates

Puffiness

Processing cultivars had higher puffiness ratings at both temperatures than nonprocessing cultivars. Puffiness was more pronounced at 30C than at 20C. The degree of puffiness exhibited among processing cultivars in order of decreasing ratings were Donore, Cascade, Pet0 94C and Advantage (data not shown).

Total Solids

Processing cultivars Dorado, Advantage, Caraibe and Cascade had total solids in the lowest range (3.0 - 3.5%) while Pet0 94C and Rio Grande occupied the mid-lower and middle ranges respectively when stored at 20C (Table 3). At 30C Pet0 94C and Cascade had the lowest TSS while Donore and Advantage had the highest total solids (Table 3). All nonprocessing cultivars had more TSS at 30C

172 M. MOHAMMED. L.A. WILSON and P.I. GOMES

than 20C except for Floradade which showed the opposite and Carnival wiuch had the same range at both temperatures (Table 3).

TAABLE 2. COLOR INDEX OF PROCESSING AND NONPROCESSING TOMATO CULTIVARS AFTER 7,

14 AND 21 DAYS AT 20C AND 30C, RESPECTIVELY

cultivanr Color Index

20c 3oc LSD 0.05 7davs 14davs 21 davs 7davs 14davs 21 davr

Processing a. Dorado. Pel0 94C 35.3'b 59.ld 59.6d 29.2a 58.2cd 58.6cd

Rio Grande, 4.1 Cascade

Donom. Neema 1401

Non Processing

a. Capitan 24.0ab 41.le 55.01 20.1a 35.lde 37.28 b. Floradade. Floradel

b. Advantage. Caraibe, 31.la 57.3cd 59.2d 27.2a 5 4 . 9 ~ 556cd

Calypso. Waiters. 27.2bc SO.@ 60.Q 24.0ab 53.3f 55.51 4.0 Early Set

c. Star Pak. Carnival 32.44 66.2h 66.6h 28% 65.lh 66.2h

' Mean of 5 fruitdtreatment x 3 replicates

Total Pectins

Total pectin content was highest for Cascade and lowest for Rio Grande. Two nonprocessing cultivars, Floradade and Capitan, had higher total pectin contents at the higher temperature than the lower temperature (Table 3).

Firmness

Fruits stored at 20C were generally f m e r than those stored at 30C (Table 3). At both temperatures processing cultivars were firmer than nonprocessing cultivars. The processing cultivars, Advantage, Dorado and Neema 1401 in order of decreasing ratings showed the iughest firmness. The corresponding nonprocessing cultivars were Floradel, Floradade and Star Pak (Table 3).

Chemical Analysis

Significant differences for the groupings of processing and nonprocessing tomato cultivars for pH, TSS and vitamin C were obtained at 20C after 7,14 and 2 1 days, respectively as shown in Table 4.

TA

BL

E 3

. TO

TAL

SOLI

DS,

TO

TAL

PEC

TIN

AN

D F

IRM

NES

S O

F PR

OC

ESSI

NG

AN

D N

ON

PRO

CES

SIN

G T

OM

ATO

CU

LTIV

AR

S A

FTER

21

DA

YS

AT 20C

AN

D 3

0C, R

ESPE

CTI

VEL

Y

Par

amet

ers

Dat

a P

roce

ssin

g'

Non

-pro

cess

ing'

8

Ran

ge

20c

30C

20

c 30

C

Tota

l Sol

ids

(%)

3.00

- 3.5

0 1,

2,5

, 8

1 3.

51 -

4.01

4.

02 -

4.52

4.

53 - 5

.02

5.03

- 5.

52

Tota

l pec

tin

9.0

- 14.

0 m

gll O

Og

14.1

- 19.

1 19

.2 - 2

4.2

24.3

- 29.

3 29

.4 - 3

4.4

3, 6

4,

7

6 1,

3.4,

5. 7

2 8

3,8

4,7

,8

1

7,2

3,5,

6 2,

6, 7

6,

1, 2

,'3, 6

, 8

1,2,

6

1,4,

5,6

2,

3,

4, 8

4 F

1, 3

.4,5

, 7

4, 5

, 7

3,4

. 5.7

2 5 E ro

C

5 8 2 8

A

Firm

ness

40

- 65

5, 7

, 8

1, 2

, 3. 4

, 5, 6

, 7, 8

2

66 - 9

1 1,

2, 3

,4, 5

, 6, 7

, 8

1 I 2,

3,4

.6

s! 8 (9

) 92

- 11

7 11

8 - 1

43

5, 6

, 7, 8

1,

2, 3

, 4

YPr

oces

sing c

ultiv

ars:

I =

Dor

ado,

2 =

Adv

anta

ge, 3

= P

et0

94C

, 4 =

Nee

ma

1401

.5 =

Car

aibe

, 6 =

Rio

Gra

nde,

7 =

Don

ore,

8 =

Cas

cade

Y

onpr

oces

sing

cul

tivan

: 1 C

alyp

so, 2

= F

lora

del,

3 =

Flo

rada

de, 4

= E

arly

Se

t. 5

= Star P

ak, 6

= C

arni

val, 7

= W

alte

rs, 8

= C

apita

n

TAB

LE 4

. C

HE

MIC

AL

AN

ALY

SIS

INC

LUD

ING

pH

, TO

TAL

SO

LUB

LE

SO

LID

S A

ND

VIT

AM

IN C

OF

TOM

ATO

CU

LTIV

AR

S S

TOR

ED

A

T 20

C F

OR

7,1

4 A

ND

21

DA

YS R

ES

PE

CTI

VE

LY

Che

mic

al a

naly

sis a

t 20C

To

mat

o C

ultiv

ars

PH

Tota

l Sol

uble

Sol

ids

(%)

Vita

min

C (m

g/lO

Og)

Pro

cess

lng

Gro

uD:

x D

orad

o, D

onor

e, P

et0

94C

4.

03'bc

4.

19de

4.

32fg

h 3.

5ab

4.2

~

4.7d

15

.2bc

17

.5cd

17

.0cd

G

rouD

: x

Adva

ntag

e, N

eem

a 14

01

4.13

cd

4.26

ef

4.48

ij 4.

lbc

4.6d

5.

1e

15.0

bc

17.0

cd

17.2

cd

-8 G

rouD

: r

Car

aibe

, Rio

Gra

nde

3.98

b 4.

18de

4.

40hi

j 3.

8bc

4.lb

c 4.

3cd

12.6

a 13

.9a

14.3

a ?

m4:

s! E !i s

7 da

ys

14da

ys

21 d

ays

7 da

ys

14da

ys

21 d

ays

7day

s 14

days

21

day

s 5 P

Cas

cade

3.

82a

4.09

bcd

4.11

cd

4.1b

c 4.

4cd

4.3c

d 15

.6bc

18

.0de

17

.1cd

Non

-pro

cess

ing

Flor

adel

, Flo

rada

de, E

arly

Set

, 4.

01bc

4.

11cd

4.

19de

3.

4a

3.7a

b 3.

9bc

19.6

de

20.0

ef

22.3

1 C

arni

val

Star

Pak

, Wal

ters

. Cap

itan

4.05

bc

4.17

de

4.38

ghi

4.3c

d 5.

51

4.0b

c 21

.0ef

20

.4ef

26

.19

Cal

ypso

4.

28ef

g 4.

39gh

i 4.

51j

4.1b

c 4.

lbc

3.6a

b 18

.4de

19

.2de

20

.1 ef

0

z 7(

d

Gm

&:

Gro

uD:

Gro

uD:

!- c1

LSD

(O.0

5)

0.12

0.

4 2.

3

'Mea

n of

5 hi

ts/tr

eatm

ent x

3 r

eplic

ates


There were si@icant increases in pH at PC0.05 level with increasing storage time for processing cultivars classified in Groups 1 to 4. Such increases in pH for nonprocessing cultivars occurred after 14 and 2 1 days, respectively for cultivars in Groups 5 and 7 only (Table 4).

Total Soluble Solids (TSS)

Processing cultivars in Groups 1 and 2 showed a progressive increase in TSS as storage duration increased by increments of 7 days (Table 4). Nonprocessing cultivars in Group 6 had higher TSS than cultivars in Groups 5 after the first two storage intervals.

Vitamin C

Vitamin C content was generally higher for nonprocessing than processing cultivars (Table 4). Processing cultivars in Groups 1, 2 and 4 were higher in vitamin C content at each storage interval than Group 3. Nonprocessing cultivars in Group 6 after 7 and 2 1 days respectively, had higher vitamin C levels than the nonprocessing cultivar Calypso in Group 7 (Table 4).

Total Titratable Acidity (TTA)

There was a significant decline in TTA for tomatoes in each group except Groups 5 and 6 after 7,14 and 21 days at 20C (Table 5 ) .

Sugar Acid Ratio

There was a general increase in sugar/acid ratio for tomatoes in each group as storage time increased by intervals of 7 days up to 21 days. Sugadacid ratio was generally higher for nonprocessing than processing cultivars (Table 6).

Sensory Evaluation

After 2 1 days at 20C mUt of cultivars Caraibe and Dorado had the best rating for flavor (Table 6). Processing cultivars with lowest ratings for flavor were


Advantage and Donore. Texture ratings were significantly different between each cultivar (Table 6). Dorado, Advantage and Cascade were highly rated above other processing cultivars for color and appearance (Table 6). A similar trend was observed for these three processing cultivars for overall acceptability.

Fruit of the cultivar Walters followed by Floradel and Carnival had among nonprocessing cultivars the best flavor ratings after 21 days at 20C. Walters and Floradel were rated among the best for texture (Table 6). Walters and Carnival had the best ratings for color and appearance as well as overall acceptability (Table 6).

TABLE 5. TOTAL TITRATABLE ACIDITY AND SUGAR ACID RATIO OF TOMATO CULTIVARS

STORED AT 20C FOR 7,14 AND 21 DAYS

Chemical analysis at 20C

7 days 14 days 21 days 7days f 4 days 21 days Tomato Cultwars Total titratable acidity Sugar acid ratio

Processing GtQba: Dorado. Donore. Peto 94C 0.42' 0.37gh 0.29de 9.6a 11.4bc 14.8de GmUL2: Advantage, Neema 1401 0.49j 0.39hi 0.331 8.4a 1l.Obc 13.6cde Ga!ULQ: Caraibe. Rio Grande 0.39hi 0.331 0.29de 10.la 12.8cd 15.lef Gmrce4: Cascade 0.41i 0.32ef 0.27cd 9.2a 12.6cd 15.0ef

Non-processing GK!Z&: Floradel, Floradade. Early Set, 0.30def 0.26cd 0.23bc ll.2bc 14.4de 16.9fg Carnival GraueG: Slar Pak. Waiters, Capitan 0.41i 0.39hi 0.22a 10.6bc 14.2de 18.6gh Greuez: Calypso 0.37gh 0.27cd 0.19a 11.2bc 15.1ef 19.2i

LSD(O.05) 0.04 2.1

Mean of 5 fruitdtreatment x 3 repllcates

DISCUSSION

Although fruits from the processing cultivars investigated in this study showed earlier ripening times and were notably firmer (Table 3) with greater resistance to physical damage than the nonprocessing cultivars, the latter genotypes were more suitable as a fresh or table fruit than the former genotypes. Accordingly, the following advantages of the fresh table tomato cultivars over processing cultivars were identified:


(1) better locule development and less puffiness (2) better texture, flavor, appearance and overall acceptability (Table 6) (3) Superior chemical quality characteristics e.g. higher sugadacid ratio and

lower pH and TTA (Tables 4, 5 ) (4) higher nutritional quality in terms of higher vitamin C values (Table 4) ( 5 ) better keeping quality at 20C in relation to uniform color development and

higher percentages marketable fruits (Tables 1, 2) Although many structural factors are known to influence fruit firmness,

Hamson (1952) reported that the fleshy pericarp appeared to be more important in conditioning firmness than skin strength, proportion and structural arrangement of wall tissue, number of locules and size of fruit. In this study pericarp thickness and firmness varied with cultivars. Thus, an equal number of processing and nonprocessing cultivars had thicknesses of 0.50mm and above. The variation in pericarp duchess shown in Table 1 supported the view expressed by Al-Shaibani et al. (1982) that pericarp thickness could be genetically controlled. In this study pericarp thickness was not related to changes in firmness during storage. Processing and nonprocessing cultivars with similar pericarp thicknesses gave different rates of decline in Fruit firmness at 20C and 30C respectively, as storage time increased. Thus factors other than physical parameters were responsible for fruit ripening and softening.

Previous researchers established that fruit ripening was accompanied by conversion of protopectin to soluble forms of pectin, although the precise mechanism of this transfonnation remains unknown (Pressey 1974). The f i e r processing cultivars e.g. Dorado, Advantage, Cascade, Rio Grande had higher total pectin contents than softer processing cultivars e.g. Caraibe or Rio Grande (Table 3). Since total pectin content of these cultivars was significantly (P < 0.05) correlated with firmness (r = 0.73), then selection of tomatoes for firmness might be achieved on the basis of selection for total pectin content.

The earlier ripening times for processing compared with nonprocessing tomatoes and the generally higher pectin contents specific to certain cultivars (Table 3) suggest a more rapid conversion of protopectin to pectin during the ripening process in the former versus the latter tomato groups. Sobotka et al. (1972) found that upon ripening, tomato protopectin was converted to pectin inhcating that firmness was related to the ripening stage. Processing cultivars changed color more rapidly (Table 2) yet maintained higher firmness ratings (Table 3). than nonprocessing cultivars, suggesting slower degradation of protopectin by the two enzymes pectinesterase and polygalacturonase than chlorophyll breakdown and pigment synthesis. Similarly, several cultivars achieved uniform color development more rapidly at 20C compared with 30C, yet at the lower temperature, fruits were fumer than the higher temperature. Thus while pigment changes during tomato ripening as described by Hobson and Davies (197 1) proceeded faster at 20C than at 3OC, conversion of protopectin to pectin proceeded faster at 30C than at

TAB

LE 6

.

CU

LTIV

AR

S O

F TO

MA

TOE

S A

FTE

R 2

1 D

AY

S A

T 20

C

SE

NS

OR

Y E

VA

LUA

TIO

N O

F P

RO

CE

SS

ING

AN

D N

ON

-PR

OC

ES

SIN

G

Sen

sory

eva

luat

ion

Cul

tivar

s 21

day

s at

20C

Pro

cess

ing

1. D

orad

o 3.

tYab

cd

2.6

~

2.2a

b 2.

4b

2. A

dvan

tage

5.

4hi

2.9d

2.

la

2.7b

c 3.

Pet

o 94

C

4.7f

gh

3.5h

3

.0~

3.

4de

4. N

eem

a 14

01

3.9d

ef

3.3f

3.

2cd

3.5d

e 5.

Car

aibe

2.

8abc

3.

8i

3.w

3.

5de

6. R

io G

rand

e 4.

9ghi

3.

8i

3.2c

d 3.

9ef

7. D

onor

e 5.

8i

4.1k

4.

1ef

4.4f

g 8.

Cas

case

3.

8cde

f 3.

5h

2.5b

3.

0cd

Flav

our "

Text

ure"

C

olor

and

App

eara

nce'

O

vera

ll Acc

epta

bilit

yY

Non

-pro

cess

ing

1. C

alyp

so

2. F

lora

del

3. F

lora

dade

4.

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20C. In view of the variation in color development (Table 2) across cultivars, it appeared that color changes were also subjected to genetic control.

Preharvest con&tions and increased susceptibility to physical and pathological damages accounted for some nonprocessing cultivars having low keeping quality, but high ratings on sensory quality evaluations. Walters for example had the best ratings for flavor, texture, appearance and overall acceptability but only 57.9% of the fruits were marketable after 21 days at 20C (Table 1). This was due to the high incidence of fruits showing damages due to blotchy ripening, catfacing and blossom end rot. Of these three physiological disorders blotchy ripening was most prominent accounting for a large percentage of unmarketable fruits. In this study, cultivar differences in susceptibility to blotchy ripening were evident, accounting for similar decreases in percentage marketable fruits for Carnival, Floradade and Star Pak. These results are in agreement with those of Resurreccion and Shewfelt (1989), although according to Dick and Shattuck (1986) limited information is available on the genetic control of this disorder.

For processing cultivars, Dorado had the best sensory quality ratings (Table 6) but at least 5 other processing cultivars had more marketable fruits at both temperatures after 21 days. Bacterial spotting and radial cracking were mainly responsible for these differences. Cascade, Rio Grande and Donore with more marketable fruits than Dorado were limited by different factors relating to each of the four sensory factors listed in Table 6. Donore had good color development (Table 2) but many fruits were off-size, and lacked external gloss. Rio Grande and Cascade had good color development (Table 2) as well as gloss, but extensive incidence of puffiness promoted fruit deformation. In addition, both Donore and Rio Grande had poor flavor (Table 6).

Tomato flavor as reported by Gull et al. (1989) and Kader et al. (1977) is largely a function of variations of sugar acid content among cultivars, as a result of the production environment or during postharvest handling. However, in this study, cultivars with the highest ratings for flavor did not always correspond with the highest rating for sugar/acid ratio or TSS (Tables 4, 5 , 6). This could be accounted for on the basis of the different effects of storage temperature and time on fruit from different cultivars. In some cultivars, particularly in longer storage regimes at the higher temperatures, the incidence of physiological disorders such as heat injury, blotchy ripening and pathological damages could account for these variations. In similar studies, Simandle et al. (1 966) reported that sugadacid ratio was not a practical indicator of flavor in tomatoes. However, it was obvious from the data in Table 5 that the higher sugarlacid ratio of nonprocessing cultivars compared with processing cultivars was adequate evidence to confirm the superior flavor of nonprocessing versus processing tomatoes. Furthermore, flavor scores for nonprocessing cultivars were significantly correlated with TSS (r = 0.81), TTA (r = 0.77), TSSI~TA (r = 0.79) and pH (r = 0.70). Similar relationshps were obtained for processing cultivars but only for TSS (r = 0.59).


The pH values of tomatoes reported here, were different than those reported by Kearney and Coffey (1983) since differences occurred between cultivars and with postharvest storage at 20C with time. The increase in pH at 20C with increased duration in storage for cultivars listed in Table 5 was also contrary to the findings reported by Crane and Zilva (1 949).

Gould (1983) examined the importance of fruit acidity as a major factor affecting the keeping quality of processing tomatoes. This explanation has merit accordmg to the results in this study, since the higher TTA of processing cultivars could explain their lower incidence of fungal infection compared with the nonprocessing cultivars (Thorne and Alvarez 1982).

Evidence of higher nutritional value in terms of higher vitamin C content of nonprocessing compared to processing cultivars is shown in Table 4. However, for both processing and nonprocessing tomatoes, intercultivar difference existed for vitamin C content similar to those reported by Warnock (1983). Such findings were contrary to those reported by Kader et al. (1 973) and Brecht et al. (1 976).

Data in Table 5 also showed that at 20C significant increases in vitamin C content with fruit ripeness were not consistent for all cultivars. These differences in vitamin C content with time in the cultivars studied add to already existing conflicting data reported by previous researchers. For example Brecht et al. (1 976) found increased vitamin C content with ripeness while Watada et al. (1976) showed no change in vitamin C content with ripeness. It could be that differences in fruit maturity as indicated in color development (Table 2) resulted in differences in vitamin C content among cultivars studied. Although, the higher vitamin C content reported earlier for nonprocessing tomatoes particularly those held at 20C offered nutritional advantages to consumers it is still not known whether vitamin C plays any direct or indirect role in tomato flavor.

The high quality attributes of a fresh market tomato identified by Kader et al. (1978) and Saltveit and Sharaf (1992) such as fruits with more than 3% soluble solids, 0.32% TTA and sugarlacid ratio of more than 10 were evident in some of the traditional cultivars such as Walters, Floradel, Calypso and Floradade and prevailed among the more recently introduced cultivars Star Pak, Early Set and Carnival. Alternatively, the processing cultivars in this study most suitable for commercial use, based on the criteria used by Gould (1 983) would be Donore, Pet0 94C, Rio Grande and Advantage. Cultivars with quality attributes categorized as dual-purpose would include Caraibe, Cascade, Dorado and Neemal401.

ACKNOWLEDGMENTS

The authors wish to thank Mr. Keshwar John and Mr. Sarran Harryram for their help in laboratory and field work. Many thanks to Caribbean Chemicals Co. Ltd. and Wyatt Co. Ltd. for supplying seeds and to Ms. Andrea Houston for typing the manuscript.


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POSTHARVEST SENSORY AND PHYSIOCHEMICAL ATTRIBUTES OF PROCESSING AND NONPROCESSING TOMATO CULTIVARS

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