scholarly journals 932 PB 530 PAL INDUCTION AND FRESH-CUT LETTUCE QUALITY

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 567f-567
Author(s):  
Gloria Lopez-Galvez ◽  
Mikal Saltveit ◽  
Marita Cantwel
Keyword(s):  
Fungal Infection ◽  
Lactuca Sativa ◽  
Phenylalanine Ammonia Lyase ◽  
Visual Quality ◽  
Wound Induction ◽  
Pal Activity ◽  
Iceberg Lettuce ◽  
Fresh Cut ◽  
Humidified Air ◽  
Kinetics Of

Phenylalanine ammonia-lyase (PAL) activity in iceberg lettuce (Lactuca sativa L.) is increased in response to several kinds of stress, including wounding, exposure to ethylene, and fungal infection. Ethylene-induced PAL activity is correlated with the discoloration and shelf-life of fresh cut lettuce (Couture et al. 1993. HortScience 28:723). The objective of this research was to further characterize the kinetics of wound-induced PAL in fresh cut lettuce. Leaves of different cvs were cut into salad pieces (1.5 × 3 cm), rinsed in chlorinated water, centrifuged manually, and placed into containers at 5 or 15C through which humidified air flowed. Samples were evaluated for overall visual quality and specific types of discoloration. Midrib tissue was also finely cut (1 × 0.5 cm) for enhanced wound-induction of PAL, which was assayed spectrophotometrically. The kinetics of PAL in midrib tissue of fine cut and salad cut lettuce were similar, with maximum activities obtained within 12-16 h at 15C and within 40-60 h at 5C. Maximum PAL levels in the fine cut lettuce were 1.5-2.0 times those observed in the salad cut pieces, and similar to those induced by ethylene. The usefulness of PAL as a predictor of the storage life of fresh cut lettuce depends on simplifying and expediting the PAL assay.

scholarly journals INDUCTION AND INACTIVATION OF PHENYLALANINE AMMONIA-LYASE IN LETTUCE IN RESPONSE TO TEMPERATURE AND PROTEIN SYNTHESIS INHIBITORS

HortScience ◽  
1992 ◽  
Vol 27 (6) ◽  
pp. 683d-683
Author(s):  
Mark Ritenour ◽  
Mikal E. Saltveit
Keyword(s):  
Protein Synthesis ◽  
Lactuca Sativa ◽  
Phenylalanine Ammonia Lyase ◽  
Protein Synthesis Inhibitors ◽  
Pal Activity ◽  
Iceberg Lettuce ◽  
Baseline Levels ◽  
Response To Temperature

Activity of phenylalanine ammonia-lyase (PAL) is critical in the induction of russet spotting (RS) in leaves of Iceberg lettuce (Lactuca sativa L.). RS is a major postharvest disorder of lettuce caused by exposure to ppm levels of ethylene at = 5C. Both PAL and RS are decreased when lettuce tissue previously exposed to ethylene is stored at = 15C or is transferred from = 5C to = 15C. To study the induction and inactivation of PAL, we exposed lettuce leaves to air ± 10 ppm ethylene at 5C for four days to initially induce high PAL levels. After four days, leaves were treated with water ± 2 mg/L cycloheximide, and transferred to air at 5 or 15 C. In leaves previously exposed to ethylene, PAL activity decreased rapidly to baseline levels within two days in non-cycloheximide treated leaves transferred to 15C. PAL activity remain elevated in the same treatment held at 5C. In leaves treated with cycloheximide and transferred to 15C, PAL did not begin to decrease until after four days. Cycloheximide treated leaves held at 5C showed increased PAL activity both two and four days after treatment.

scholarly journals EFFECT OF TIME/TEMPERATURE TREATMENTS ON PHENYLALANINE AMMONIA-LYASE ACTIVITY AND DEVELOPMENT OF RUSSET SPOTTING IN ICEBERG LETTUCE

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1127c-1127
Author(s):  
M.A. Ritenour ◽  
M.E. Saltveit ◽  
M.J. Ahrens
Keyword(s):  
Phenylalanine Ammonia Lyase ◽  
Phenolic Content ◽  
Subjective Evaluation ◽  
Pal Activity ◽  
Iceberg Lettuce ◽  
Lyase Activity ◽  
Highly Correlated ◽  
Phenylalanine Ammonia Lyase Activity ◽  
Kinetics Of ◽  
Practical Implications

Russet spotting (RS) is an important postharvest disorder in Iceberg lettuce (Lactuca sativa L.). Previous studies showed that RS is induced by exposure to ∼5 ppm (ul/l) ethylene at ∼5C for 3 days and is characterized by the appearance of 1 to 2 mm diam. oval, brown sunken spots along the midrib. Increases in phenylalanine ammonia-lyase (PAL) activity and phenolic content are highly correlated with RS development. Ethylene-induced PAL activity is much less at higher (12C) or lower (0C) temperatures. In this study isolated whole leaves were exposed to a log series of ethylene concentrations from 0.1 to 10 ppm at temperatures from 0.0C to 20C for up to 8 days. Tissue was transferred among these various treatments to investigate the kinetics of PAL induction, activity and deactivation, phenolic accumulation, and RS development. A subjective evaluation was then made of RS development using a 1 to 9 scoring system in which 1 was no RS, and then PAL activity and phenolic content were measured. Preliminary results indicate that ethylene-induced PAL activity was decreased more rapidly upon transfer to temperatures above 10C than to 0.0C. Accumulation of phenolic compounds and development of RS paralleled each other, and were positively related to PAL activity. Practical implications of these results will be discussed.

Effect of Ozonated Water Treatment on Microbial Control and on Browning of Iceberg Lettuce (Lactuca sativa L.)

2006 ◽  
Vol 69 (1) ◽  
pp. 154-160 ◽  
Author(s):  
SHIGENOBU KOSEKI ◽  
SEIICHIRO ISOBE
Keyword(s):  
Water Treatment ◽  
Lactuca Sativa ◽  
Combined Treatment ◽  
Microbial Control ◽  
Hot Water ◽  
Pal Activity ◽  
Iceberg Lettuce ◽  
A Value ◽  
Lactuca Sativa L ◽  
Ozonated Water

We examined the effect of ozonated water treatment on microbial control and quality of cut iceberg lettuce (Lactuca sativa L.). Fresh-cut lettuce was washed in ozonated water (3, 5, and 10 ppm) for 5 min at ambient temperature. The native bacterial population on the lettuce declined in response to a rise in ozone concentration. However, there was no further bacterial reduction (1.4 log CFU/g) above 5 ppm ozone. Although ozonated water treatment increased the phenylalanine ammonia lyase (PAL) activity of the lettuce stored at 10°C compared with the water wash treatment after 1 day of storage, the concentration of ozone did not affect PAL activity. The a* value of the residue of the lettuce methanol extracts, which reflects the extent of browning, increased dramatically in lettuce treated with 10 ppm ozonated water compared with other treatments. Treatment with 3 or 5 ppm ozonated water resulted in more rapid changes in the a* value than after the water treatment. The combined treatment of hot water (50°C, 2.5 min) followed by ozonated water (5 ppm, 2.5 min) had the same bactericidal effect as treatment with ozonated water (5 ppm, 5 min) or sodium hypochlorite (NaOCl, 200 ppm, 5 min), giving a reduction in bacteria numbers of 1.2 to 1.4 log CFU/g. The ascorbic acid content of the lettuce was not affected by these treatments. The combined treatment of hot water followed by ozonated water greatly inhibited PAL activity for up to 3 days of storage at 10°C. Treatment with this combination greatly suppressed increases in the a* value, thus retarding the progress of browning compared with other treatments throughout the 6-day storage. NaOCl treatment also inhibited browning for up to 3 days of storage. Bacterial populations on the lettuce treated with sanitizers were initially reduced but then showed rapid growth compared with that of the water wash treatment, which did not reduce bacterial counts initially.

scholarly journals Effects of Gamma Irradiation, Modified Atmosphere Packaging, and Delay of Irradiation on Quality of Fresh-cut Iceberg Lettuce

HortScience ◽  
2011 ◽  
Vol 46 (2) ◽  
pp. 273-277 ◽  
Author(s):  
Xuetong Fan ◽  
Kimberly J.B. Sokorai
Keyword(s):  
Gamma Irradiation ◽  
Modified Atmosphere Packaging ◽  
Visual Quality ◽  
Modified Atmosphere ◽  
Cut Edge ◽  
Quality Deterioration ◽  
Iceberg Lettuce ◽  
Fresh Cut ◽  
Tissue Browning

This study was conducted to investigate the effect of modified atmosphere packaging (MAP) and delay of irradiation application on the quality of cut Iceberg lettuce. Overall visual quality and tissue browning of cut lettuce were evaluated using a scale of 9 to 1, whereas texture was analyzed instrumentally during 14 days of storage at 4 °C. Results showed that irradiation (0.5 and 1.0 kGy) of cut lettuce induced tissue browning when stored in air; however, when cut lettuce was stored in MAP, irradiated lettuce had better appearance than the non-irradiated ones as a result of lower O2 levels in the packages of irradiated samples compared with the levels in control packages. In general, irradiation at doses of 0.5 and 1.0 kGy did not affect firmness of the lettuce. After 14 days of MAP storage, overall visual quality of non-irradiated samples had a score of ≈4, a score below the limit of sales appeal, whereas the two irradiated samples had scores of 6.5 to 7.9, indicating the irradiated samples had a fair to good quality. Delaying irradiation by 1 day after preparation of cut lettuce did not significantly (P > 0.05) affect cut edge browning, surface browning, or overall visual quality compared with lettuce irradiated immediately after preparation. Our results suggest that MAP is essential to minimize quality deterioration caused by irradiation.

Activity of phenylalanine ammonia-lyase, peroxidase and polyphenol oxidase in roots of banana (Musa acuminata AAA, cvs Grande Naine and Yangambi km5) before and after infection with Radopholus similis

Nematology ◽  
2006 ◽  
Vol 8 (2) ◽  
pp. 201-209 ◽  
Author(s):  
Nathalie Wuyts ◽  
Rony Swennen ◽  
Dirk De Waele
Keyword(s):  
Polyphenol Oxidase ◽  
Phenylalanine Ammonia Lyase ◽  
Phenylpropanoid Pathway ◽  
Musa Acuminata ◽  
Resistant Cultivar ◽  
Radopholus Similis ◽  
Wound Induction ◽  
Pal Activity ◽  
Before And After ◽  
Burrowing Nematode

AbstractPhenylpropanoids – phenolic compounds – take part in the wound and defence responses of plants and are frequently correlated with resistance. Enzymes directly or indirectly functional in the phenylpropanoid pathway are induced in plants in response to wounding and infection by pathogens, including sedentary endoparasitic nematodes. The activity of three of these enzymes, phenylalanine ammonia-lyase (PAL), peroxidase (PO) and polyphenol oxidase (PPO), was analysed in banana roots before and 1, 3 and 7 days after inoculation with the burrowing nematode Radopholus similis and in comparison with mechanically wounded roots. Constitutive activities of PAL, PO and PPO were lower in the resistant cv. Yangambi km5 (Musa acuminata AAA) than in the susceptible cv. Grande Naine (Musa acuminata AAA). During the experiment, levels increased to those of cv. Grande Naine, but only for R. similis-inoculated roots of cv. Yangambi km5 enzyme activities at 3 and 7 days after the onset of the experiment were values significantly higher than constitutive ones. At 7 days after the treatments, PO activity was significantly higher in wounded roots of cv. Grande Naine than in control and nematode-inoculated roots. The level of PAL activity in nematode-treated roots of cv. Yangambi km5 at 7 days after inoculation was 2.3-fold higher than control and wounded roots and up to six-fold higher than cv. Grande Naine roots. We concluded that PAL was induced in R. similis-inoculated roots of the resistant cultivar only and that this response was different from wound induction. For PO and PPO we concluded that levels in the resistant cultivar increased to those of the susceptible cultivar as a response to general stress in the plants during the experiment. Nevertheless, final levels of PO and PPO activity in R. similis-inoculated roots of the resistant cultivar were significantly higher than constitutive ones.

scholarly journals Indole-3-acetic Acid (IAA) Content and Axillary Bud Development in Relation to Russet Spotting in Harvested Iceberg Lettuce

1996 ◽  
Vol 121 (3) ◽  
pp. 543-547 ◽  
Author(s):  
Mark A. Ritenour ◽  
Ellen G. Sutter ◽  
David M. Williams ◽  
Mikal E. Saltveit
Keyword(s):  
Phenylalanine Ammonia Lyase ◽  
Axillary Bud ◽  
Poor Correlation ◽  
Bud Development ◽  
Pal Activity ◽  
Iceberg Lettuce ◽  
Harvest Dates ◽  
Highly Correlated ◽  
Growing Conditions ◽  
Indole 3 Acetic Acid

This study was undertaken to determine if endogenous IAA content and axillary bud development correlate with phenylalanine ammonia-lyase (PAL) induction and russet spotting (RS) susceptibility among RS susceptible and resistant cultivars of Iceberg lettuce (Lactuca sativa L.). Final levels of ethylene-induced PAL activity and RS development were highly correlated among cultivars, field conditions, and harvest dates. Harvested Iceberg lettuce midribs contained relatively low amounts of free IAA (maximum of 5.2 ng·g-1 fresh weight). There was poor correlation between free IAA content in lettuce leaf midribs and final RS development among all cultivars, growing conditions, and harvest dates. Axillary bud development, as measured by the number of visible buds per head, bud weight, or bud length, were not significantly correlated with final RS development or midrib IAA content. Cultivars with higher initial free IAA content lost much of their IAA after 8 days storage at 5C in air ± ethylene.

Impact of different washing procedures on quality of fresh-cut iceberg lettuce (Lactuca sativa var. capitata L.) and endive (Cichorium endivia L.)

2012 ◽  
Vol 236 (2) ◽  
pp. 229-241 ◽  
Author(s):  
Sabine Wulfkuehler ◽  
Lisa Kurfiss ◽  
Dietmar R. Kammerer ◽  
Agnes Weiss ◽  
Herbert Schmidt ◽  
...  
Keyword(s):  
Lactuca Sativa ◽  
Iceberg Lettuce ◽  
Cichorium Endivia ◽  
Fresh Cut

scholarly journals Wound-induced Phenolic Accumulation and Browning in Lettuce (Lactucasativa L.) Leaf Tissue is Reduced by Exposure to n-alcohols

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1131B-1131
Author(s):  
Mikal Saltveit ◽  
Youngjun Choi ◽  
Francisco Tomás-Barberán
Keyword(s):  
Phenylalanine Ammonia Lyase ◽  
De Novo ◽  
Physiological Responses ◽  
Leaf Tissue ◽  
De Novo Synthesis ◽  
Phenolic Metabolism ◽  
Pal Activity ◽  
Wound Signal ◽  
Fresh Cut ◽  
Tissue Browning

A wound signal originates at the site of injury in lettuce [Lactucasativa (L.)] leaf tissue and propagates into adjacent tissue where it induces a number of physiological responses that include increased phenolic metabolism with the de novo synthesis of phenylalanine ammonia lyase (PAL, EC 4.3.1.5), the synthesis and accumulation of soluble phenolic compounds (e.g., chlorogenic acid), and subsequent tissue browning. Exposing excised mid-rib leaf tissue to vapors (20 μmol·g-1 FW) or aqueous solutions (100 mm) of n-alcohols inhibited this wound-induced tissue browning by 40% and 60%, respectively. Effectiveness of the alcohol increased linearly from ethanol to the seven-carbon heptanol, and then was lost for the longer n-alcohols 1-octanol and 1-nonanol. The 2- and 3-isomers of the effective alcohols did not significantly reduce wound-induced phenolic accumulation at optimal 1-alcohol concentrations, but significant reductions did occur at much higher concentrations (100 μmol·g-1 FW) of the 2-, and 3-isomers. The active n-alcohols were maximally effective when applied during the first 2 h after excision, and were ineffective if applied 12 h after excision. Phospholipase D (PLD) and its product phosphatidic acid (PA) are thought to initiate the oxylipin pathway that culminates in the production of jasmonic acid, and PLD is specifically inhibited by 1-butanol, but not by 2- or 3-butanol. These results suggest that PLD, PA, and the oxylipin pathway may be involved in producing the wound signal responsible for increased wound-induced PAL activity, phenolic accumulation, and browning in fresh-cut lettuce leaf tissue.

scholarly journals Early Changes in Wound-induced and Ethylene-induced Phenylpropanoid Metabolism in Lettuce

HortScience ◽  
1996 ◽  
Vol 31 (4) ◽  
pp. 599f-599
Author(s):  
F.A. Tomás-Barberdán ◽  
J. Loaiza-Velarde ◽  
M.E. Saltveit
Keyword(s):  
Phenolic Compounds ◽  
Leaf Tissue ◽  
Quinic Acid ◽  
Early Response ◽  
Phenylpropanoid Metabolism ◽  
Mechanical Wounding ◽  
Phenolic Metabolism ◽  
Iceberg Lettuce ◽  
Humidified Air ◽  
Kinetics Of

Mechanical wounding and exposure to ethylene induces an increase in phenylpropanoid metabolism in lettuce and an increase in the concentration of several soluble phenolic compounds that are easily oxidized to brown substances by polyphenol oxidase. To study the early response of lettuce to wounding and ethylene, leaves of iceberg, butter leaf, and Romaine lettuces were either wounded or exposed to ethylene at 10 μL·L–1 in flows of humidified air at 5 or 10°C. Soluble phenolic compounds were extracted at intervals up to 72 hours and were analyzed by HPLC. After 72 hours, wounded leaves of all three lettuce types showed elevated levels of caffeoyl tartaric acid, Chlorogenic acid, dicaffeoyl tartanc acid, and 3,5-dicaffcoyl quinic acid at both temperatures. In contrast, there were no significant increases in soluble phenolic compounds in iceberg lettuce exposed to ethylene at 10°C. At 5°C for iceberg, and at both temperatures for the other two types, there was the same pattern for ethylene treated and wounded leaf tissue. The kinetics of wound and ethylene-induced phenolic metabolism are different and will be discussed in relation to phenolics produced and browning susceptibility.

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