POSTHARVEST RETARDATION OF SENESCENCE IN SHAD0 BENNI (ERYNGZUM FOETZDUM, L.) PLANTS

MAJEED MOHAMMED' and LYNDA D. WICKHAM

Department of Crop Science Faculty of Agriculture

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

Accepted for Publication September 12, 1994

ABSTRACT

Leaves of shado benni plants (Eryngium foetidum, L.) are used extensively as a seasoning and herbal medicine. However, the very short shelj-life of 3-4 days of harvested plants is a major drawback to wider use. Plants were harvested with roots intact, dipped in gibberellic acid (GAJ and stored in perforated and nonperforated LDPE bags up to 22 days at 20-22C and 28-30C. Samples were examined for changes in appearance, color, fresh weight and flavor (loss of pungency and off-ji'avor development). GA, effectively retarded plant senescence up to 22 days at both temperatures when stored in nonperfora- ted LDPE bags. Despite the external maintenance of marketable quality, flavor life was 17 days since development of off-flavors and reduction in pungency occurred after this period. Thus, the combination ofpolyethylene packaging, GA, dip treatment and reduced temperature storage extended the shelf-life of shado benni plants in a fresh, turgid and decay-free condition for in excess of two weeks.

INTRODUCTION

The culinary herb, Eryngium foetidum, L., known popularly as shado benni in the islands of the Caribbean, is increasingly becoming an item of international trade, specifically to satisfy demands of ethnic populations in western developed countries. It is used extensively in some islands of the Caribbean and in Asia, especially in India and Korea. The herb is used mainly as a seasoning in the preparation of a range of foods, including vegetable and meat dishes, chutneys,

'To whom correspondence should be sent.

Journal of Food Quality 18 (1995) 325-334. All Rights Reserved. "Copyright 1995 by Food & Nutrition Press, Inc.. Trumbull, Connecticut. 325

326 M. MOHAMMED and L.D. WICKHAM

preserves, sauces and snacks. Although generally used in small quantities, its unique aroma adds the characteristic flavor to preparations in which it is used, and this largely accounts for its increasing demand among ethnic populations. Perhaps the closest seasoning to this herb, with respect to flavor, is cilantro, which has itself been made popular by the growing demand for Mexican cuisine. Shado benni is also used in herbal medicine and is reported to be beneficial in the treatment of a number of ailments (Wong 1976).

Shado benni grows as a small rosette plant from which individual leaves are clipped for use. It is marketed either as bundles of individual leaves or as the entire plant minus the roots. The herb is mainly utilized in the fresh, green state and has an extremely short shelf life, i.e., 3-4 days under the normal, tropical, ambient conditions in which it is produced (Mark 1989). Visible senescent changes include rapid chlorosis, wilting and the development of brown necrotic lesions on the leaves, usually as a result of fungal invasion. Even more important, however, are changes in flavor which accompany the visual deterioration. First, there is a reduction in intensity of the characteristic desirable flavor, followed by the development of off-flavors characterized by a sour, musty taste which together make the product useless as a seasoning. These changes are more commonly observed in international trade where time from harvest to market is inevitably longer. Unfortunately, it is also where losses are more expensive. This study investigated means of extension of the shelf-life of shado benni through the use of postharvest GA, dips with particular emphasis on the retardation of senescent changes and the maintenance of flavor quality.

MATERIALS AND METHODS

Shado benni (Eryngium foetidum, L.) plants were hand-harvested with the major portion of their roots intact. Immediately after harvest, plants were rinsed to remove the bulk of adhering soil from the roots and leaves and then submerged in water in plastic buckets for transportation to the laboratory within 2 h of harvest. Roots were trimmed to a maximum length of 10 cm and all decayed and damaged leaves or floral parts were removed to simulate export marketing requirements. Plants for treatment were then selected based on size, color and condition to give only plants of export marketable quality. Each plant had a maximum of 5 leaves. A11 plants were again submerged in tap-water containing 500 ppm sodium hypochlorite solution in plastic containers (20 L capacity) for 20 min to control surface pathogens. Plants were spread on a single layer on absorbent paper and left for 15 min under an oscillating fan in an air-conditioned room (21-22(3, 50-55 5% R.H.) until surface moisture had evaporated.

RETARDATION OF SENESCENCE IN SHAD0 BENNI 321

Immediately following this, the plants were dipped for 10 min either in a solution of 200 ppm GA, or 400 ppm GA, (Sigma Chemical Co., St. Louis). The control plants were dipped in water only. Following the dip treatments, plants were again surface dried as above. Plants were then selected at random and sealed, in groups of five, in perforated (30 pinholes/bag) and nonperforated low density polyethylene bags (LDPE), 25.4 pm thick (gas transmission rates at 22C, 1 atm.: 1350 ml m-’h-’ CO,; 500 ml m-*h-’ 0,) and stored in ventilated cardboard cartons in single layers in separate storage rooms at 20-22C and 60-70% R.H. and 28-30C and 55-65% R.H. up to 22 days. Plants were assessed at regular intervals up to 22 days for percentage fresh weight losses, appearance, flavor and color.

The weight of each plant was taken before and after each storage interval for calculation of percentage fresh weight losses. Appearance was assessed using a hedonic scale from 1-9 with: 1 : leaves with uniform green color, turgid, fresh with no marks or streaks; 3: leaves with uniform green color, slight shriveling, no decay or discoloration; 5: leaves with slight discoloration and shriveling and no decay; 7: leaves with moderate discoloration and shriveling and no decay (limit to marketability) and 9: leaves with visible symptoms of decay, complete discoloration and shriveling.

Leaf color was obtained using a portable tristimulus Minolta Chromameter (Model CR-200, Minolta Corp, Ramsey, NJ). The meter was calibrated with a white standard (Minolta calibration plate CR-A43) and the leaf chromaticity was measured in ‘L’, ‘a’, ‘b’ coordinates. Color component ‘L’ represents the value (lightness) of colors and is larger for lighter colors; ‘a’ is negative for green and positive for red; and ‘b’ is negative for blue and positive for yellow (Singha er al. 1991). In this study the color components ‘L’ and ‘b’ were used to quantify leaf color with higher values signifying a reduction in appearance at the start and at each storage interval of the experiment as described by Hicklenton (1991). Measurements were taken at three locations chosen at random on the upper leaf surface of each plant.

A panel consisting of 24 members was used for the taste test. A multiple comparison test was conducted using shado benni leaves from each treatment. A chutney was used to facilitate the evaluation for flavor pungency and development of off-flavors, since it represents one of the most common method of utilizing shado benni leaves in food preparations. A 10-g portion of leaves, 100 g of unripe mango and 10 ml of water were mascerated for 2 min in a 16 speed Oster blender together with 3 g of sodium chloride and 6 g of garlic to make a chutney. A cooked puff made of wheat dough was eaten with the chutney to assist in detection of changes in the intensity or development of off-flavors in the stored leaves. The evaluation was done at room temperature in duplicate among panelists. Samples of the chutney from each treatment were compared to a reference sample that was made from freshly-harvested leaves.

328 M. MOHAMMED and L.D. WICKHAM

The panelists were required to indicate whether they rated the treatment samples more acceptable, equal to or less acceptable for flavor than the reference sample and whether the degree of the intensity of shado benni taste was 1: normal, 2: fairly normal; 3: moderately normal (limit for commercial acceptability); 4: slight and 5: none.

Koch’s postulate (Brathwaite 1981) was carried out on decayed plants to determine the fungi that were responsible for decay as described previously by Mohammed and Wickham (1993).

The experiment consisted of three replicates with each replicate containing five plants. Data were analyzed as a completely randomized design with a factorial arrangement of variables, and significance tested by the F-test and LSD where applicable, after transformation for ranking (Steel and Torrie 1960).

RESULTS AND DISCUSSION

Under normal tropical ambient conditions, shado benni plants become unsalable in less than 3-4 days (Mark 1989). In this study, postharvest application of gibberellic acid was found to extend marketability due to appearance more convincingly than prolonging flavor life over controls. GA, treated plants appeared marketable up to 22 days at both storage temperatures, respectively, in nonperforated LDPE bags. The most effective treatment for retardation of senescence of shado benni plants was exogenous application of 200 ppm GA, followed by storage in nonperforated LDPE bags. With this treatment plants maintained their uniform green color, had no decay, required no trimming of wilted or desiccated leaves and still had a moderately normal flavor and appearance up to 17 days (Tables 1 , 2, 3). Thereafter, marked development of off-flavors characterized by a distinct sour and musty taste and odor leading to a reduction in intensity of the typical shado benni flavor occurred.

The appearance of shado benni plants was significantly reduced (P I 0.01) when kept at 28-30C compared with 20-22C (Table 1). This reduction in quality was characterized by increased yellowing and browning at the leaf margins spreading inwards to the midribs as storage duration increased from 7 to 22 days. For example at 28-30C the mean values of ‘L’ and ‘b’ after 22 days were 21.2 (+ SEM 0.40) and 0.48 (* SEM 0.03), respectively (Table 2). For plants stored at 20-22C for the same length of time, equivalent index values were 18.6 (+ SEM 0.50) and 0.50 (+ SEM 0.03) (Table 2).

Fresh weight losses were also higher at the warmer temperature (Fig. l), which also contributed to increased shriveling and lower ratings for appearance particularly for GA,-treated plants (Table 1). The higher rate of respiration at

RETARDATION OF SENESCENCE IN SHADO BENNI 329

TABLE 1. APPEARANCE RATINGS IN SHADO BENNI PLANTS DIPPED IN DIFFERENT GA,

IN POLYETHYLENE BAGS CONCENTRATIONS AND STORED AT 20-22C AND 28-30C UP TO 22 DAYS

Appearance'

Other Treatments Days at 20-22C Days at 28-30C

7 12 17 22 7 12 17 22

Perforated LDPE

(a) No dip 4.9b 6.2d 6 . 8 ~ 8.71 3.6a 6 . 4 ~ 7.0d 8.8f

(b) 220 ppm GA, 3.3a 5.lb 6.0d 8.8f 3.8a 6 . 6 ~ 7.0d 9.0f

(c) 400 ppm GA, 3.8a 5 . 5 ~ 5 . 6 ~ 8.5f 4.3b 6 . 6 ~ 7.6e 9.0f

LSD (0.01) (kO.37) (k0.25)

Nonperforated LDPE

(a) No dip 4.5b 4.7bc 5.5d 7.0f 3.9b 5 . 0 ~ 6.6f 6.9f

(bf 200 ppm GA, 2.7a 4.7bc 4 . 9 ~ 5.4d 3.0a 5 . 0 ~ 5.3d 5.8e

(c) 400 ppm GA, 3.0a 4.5b 4.8bc 6.0e 3.0b 4 . 9 ~ 5.3d 6.8f

LSD (0.01) (k0.31) (f0.21)

'Appearance 1-9 with 1 = Uniform green leaves, turgid with no streaks, 7 = being the limit to marketability and 9 = leaves with moderate symptoms of decay, complete discoloration and shriveling.

28-30C may have aided this acceleration of senescence. In addition, the vapor pressure deficit in the storage environment at the higher temperature would have been greater than at the lower temperature, resulting in higher water loss and higher appearance ratings (Table 1, Fig. 1) indicating more rapid deterioration. These observations further demonstrated the importance of proper temperature and relative humidity management in order to maintain optimum quality.

The data presented in Tables 1 and 2 for appearance and color, respectively, confirmed previous studies (Back and Richmond 1969; Fletcher et aE. 1969; Aharoni and Ben-Yehoshua 1973; Hicklenton 199 1) of the senescence-retarding properties of GA, on leafy vegetables and their suitability for commercial

TABL

E 2.

CO

LOR

CH

AN

GES

IN S

HA

D0

BEN

NI P

LAN

TS D

IPPE

D IN

DIF

FER

ENT

GA,

CO

NC

ENTR

ATI

ON

S A

ND

STO

RED

AT

20-2

2C A

ND

28-

30C

UP

TO 2

2 D

AY

S IN

PO

LYET

HY

LEN

E BA

GS

w 8

~

Col

or C

hang

esz

~ ~~

~

Day

s at

20-

22C

D

ays

at 2

8-30

C

Trea

tmen

ts

7 1

2

17

2

2

7 12

1

7

22

z 5 G

----

---

----

---

____

__ -

----

-- _

__

__

_-_

_- ----c-

----

Lb

Lb

Lb

Lb

Lb

Lb

Lb

Lb

X

__----_-______________I---- -

Perfo

rate

d LD

PE

i3 (a

) N

o D

ip

15.8

0.

44

16.1

0.

45

19.6

0.

47

19.9

0.

49

15.5

0.

45

16.7

0.

47

18.0

0.

49

23 6

0.

52

B r tl

(b)

200

ppm

GA3

16

.2

0.44

15

9 0.

44

19.5

0.

44

19.9

0.

47

i5.9

0.

44

16.3

0.

44

19.2

0.

44

19.6

04

6

i

8 E

(c)

400

ppm

GA3

15

.3

0.43

15

.0

0.44

17

.6

0.44

18

.8

0.46

17

.5

0.44

17

.5

0.44

17

.7

0.44

20

.4

0.45

LSD

(0.

05)

(0.0

4)

(0.0

4)

(0.5

1)

(0.0

3)

(0.6

6)

(0.0

4)

(0.7

1)

(0.0

3)

(0.5

0)

(0.0

4)

(0.3

7)

(0.0

5)

(0.3

9)

(0.0

6)

(1.0

1)

(0.0

5)

Non

pe rf

ora t

ed L

D P E

(a)

No D

ip

16.4

0.

42

16.7

0.

43

17.1

0.

44

19.9

0.

45

16.5

0.

42

15.8

0.

44

16.5

0.

48

21.6

0.

53

(b)

200

ppm

GA3

17

.3

0.41

17

.5

0.42

17

.4

0.42

17

.7

0.44

16

.7

0.45

13

.9

0.46

15

.1

0.46

17

.6

0.49

(c)

400

ppm

GA3

15

.3

0.41

15

.4

0.42

16

.8

0.42

16

.6

0.43

17

.1

0.45

15

.9

0.45

15

.6

0.46

16

.5

0.47

LSD

(0.

05)

(0.4

4)

(0 0

5)

(0.5

2)

(0.0

3)

(0.6

6)

(0.0

4)

(0.8

0)

(0.0

3)

(0.7

7)

(0.0

5)

(0.9

0)

(0.0

7)

(0.3

6)

(0.0

4)

(0.7

6)

(0.0

4)

Z M

ean

valu

es fo

r L

and

b im

med

iate

ly a

fter

harv

est w

ere

14.7

and

0.4

0, re

spec

tivel

y.

RETARDATION OF SENESCENCE IN SHADO BENNI 33 1

TABLE 3. TASTE PANELIST ASSESSMENT OF THE FLAVOR OF SHADO BENNI LEAVES AS INFLUENCED BY EXOGENOUS APPLICATIONS OF GA, AND STORAGE OF UP TO

22 DAYS AT TWO TEMPERATURES

Panelist assessment of flavor"

Treatments Days at 20-22C Days at 28-30C

7 12 17 22 7 12 17 22

Perforated LDPE

(a) No dip 1.0 2.0 2.4 4.2 1.0 2.2 2.2 4.0

(b) 220 ppm GA, 1.0 2.2 2.3 3.5 1.0 2.2 2.2 3.8

(c) 400 ppm GA, 1.0 2.5 3.2 4.0 1.0 3.5 3.6 3 .8

LSD (0.05) ( fI .03) (k 1.05)

Nonperforated LDPE

(a) No dip 1.0 2.0 3.0 3.4 1.0 2.2 2.6 4.0

(b) 200 ppm GA, 1.0 2.2 2.8 4.2 1.0 2.5 3.0 4.3

(c) 400 ppm GA, 1.0 2.8 2.8 3.8 1.0 2.7 2.8 3.8

LSD (0.05) (* 1.10) (k.1.07)

'Appearance score 1-5 1 = normal, 2 = fairly normal, 3 = moderately normal, 4 = slightly and 5 = none.

application as indicated by Chin and Beevers (1970) and Fletcher et al. (1969). Accordingly at both temperatures over the entire 22 days, GA, treated plants in nonperforated LDPE bags (Table 1) only and both types of bags generally at 17-22 days (Table 2) had equal or superior ratings for appearance and color than control plants.

Thus, the effectiveness of GA, in extending the shelf-life of shado benni plants depended on the storage temperature, the concentration of GA, applied and the modified atmosphere created within the perforated and nonperforated LDPE bags. It is recommended that a postharvest dip of GA, at 200 ppm rather than 400 ppm be used for shelf-life extension in shado benni plants because the difference in the effects of both concentrations on overall appearance and flavor

332

30 -

20 -

10 -

M. MOHAMMED and L.D. WICKHAM

- -m -. PERFORATED 20-22 C

NON PERFORATED 2022C

40 1 - -. -. PERFORATED 28-3W

DAYS

FIG. 1. PERCENTAGE FRESH WEIGHT LOSSES OF SHAD0 BENNI PLANTS DIPPED IN

DAYS IN PERFORATED AND NONPERFORATED POLYETHYLENE BAGS 200 PPM GA, CONCENTRATIONS AND STORED AT 20-22C AMD 28-30C UP TO 22

is not sufficient to justify using more GA,. After 17 days at both temperatures the same ratings for appearance for plant in the nonperforated LDPE bags at 22 days and the ‘b’ color index value for plants in both types of bags were recorded. Beyond 17 days, despite the better retention of color noted by lower ‘L’ and ‘b’ values, respectively (Table 2), in addition to the higher ratings for overall appearance (Table 1) at 200 ppm GA, compared with controls, off-flavor development and reduced intensity of shado benni taste were obtained. Additionally, both the cost of the treatment and possible residual levels of GA, would be lower with the use of lower concentration.

Undoubtedly, the saturated microenvironment developed within the nonper- forated LDPE bags imposed less water stress on plants resulting in significantly (P I 0.01) lower percentages fresh weight losses at each storage interval (Fig. 1). After 22 days plants in perforated bags had more discoloration, accounting for higher ‘L’ and ‘b’ values (Table 2) and lower ratings for appearance (Table 1) than plants in nonperforated bags. These evaluations corresponded with an increase in decayed plants with the pathogen identified as Phytophthora sp. Decay was manifested as irregular dark-brown areas composed of tiny sunken spots interspersed with larger yellowish-brown areas in the leaf tissue. These symptoms were totally absent from plants examined from nonperforated bags even after 22 days at 28-30C. The retardation of yellowing and decay by GA,

RETARDATION OF SENESCENCE IN SHAD0 BENNI 333

at 400 ppm after 17 days at 20-22C was not consistent at the higher tempera- tures or the longer duration. These differences in rot retardation may have depended on the type of rot; since much of the decay in samples taken from nonperforated bags after 22 days at both temperatures was caused by fungi associated with field infections and senescent retardants would not be expected to affect these. However, the higher incidence of rot in the more senesced leaf tissues from the perforated LDPE bags as against the nonperforated bags after 22 days suggest that GA, probably reduced rots that are typical of aging tissues.

Apparently the effectiveness of a greater modified atmosphere in samples from the nonperforated bags in reducing decay and yellowing in this study was particularIy pronounced as a result of the greater alleviation of water stress and the likelihood of a greater accumulation of CO, and lower concentration of 0,, although in this study these gases were not measured.

In view of FDA restrictions on GA, for postharvest use on fruits, vegetables and spices in the USA, further investigations are currently being undertaken to investigate the effect of preharvest applications of GA, on marketable quality, flavor life and biochemical changes of shado benni plants during prolonged storage.

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