Angled luffa, bitter melon, fuzzy melon, yard-long bean... Postharvest handling of Asian specialty vegetables under study

Ru-Jing Zong u Marita I. Cantwell D Leonard L. Morris

The Asian specialty vegetables ture fruits of a related species are used for transported at ambient temperature to the bitter melon, fuzzy melon, luffa their fibers, and are often called Mann Laboratory at UC Davis. On the and yard-long bean require good or luffas. The bitter melon, balsam same day the vegetables were selected for temperature management during pear or bitter (Momordicn clwrnntia) uniformity of size and freedom from de- is a white- to green-colored immature fruit fects, placed in glass containers kept at in- postharvest handling to reduce with a warty appearance; as the name sug- dicated temperatures and ventilated with deterioration and to a void chilling gests, it is valued for its unique bitter fla- humidified air at rates sufficient to main- injury. These vegetables can be vor. Fuzzy melon or Chinese squash tain carbon dioxide levels at 10.5%. Respi- successfully marketed for 1 to 2 (Renincasa hispida) is an immature green- ration and ethylene production rates were weeks if kept at 70" to 12.5"C colored cylindrical fruit with many determined from 1-ml gaseous samples bristlelike trichomes, and is harvested and analyzed on an infrared analyzer and a (50 O to 55°F). cooked lightly like summer squash. Fruits gas chromatograph equipped with a flame of some varieties may be left to mature to ionization detector, respectively (table 1). Expanding production of specialty veg- become the long-storing, edible "wax Each storage treatment consisted of three etables in the during the last gourds." The yard-long bean or asparagus replications of three to five fruits, except decade is a result of increased ethnic di- bean (Vigna sesqztipednlis) is an immature for yard-long bean, which had 10 fruits versity in our population, renewed em- legume pod, consumed much as qeen per replicate. phasis on eating healthy foods, and the beans are, but having a richer flavor. The vegetables were evaluated for successful promotion of greater variety in Our study sought to describe the quality periodically during storage and af- our diets. Many California-grown spe- postharvest characteristicsof these four ter transfer from colder storage tempera- cialty vegetables marketed locally and re- vegetables, to provide handling recom- tures to 15°C (59°F) to simulate marketing gionally originated in subtropical or tropi- mendations, and to emphasize postharvest conditions (table 2). Visual quality, seed cal areas and are sensitive to chilling, a changes that occur in all chilling-sensitive development and other growth-related characteristic that challenges distributors horticultural products. changes, color, chilling symptoms (pitting, to maintain quality. Four speaalty veg- surface discolorations),and decay were etables of Asian origin are considered here. Experiment sites and methods rated on a scale of 1 to 9, where 1 = mini- Angled luffa or Chinese (Luffa The experimental materials were har- mum expression and 9 = maximum ex- acutanguln), a green-colored immature vested at typical commercial maturity pression. For overall visual quality, a score fruit with longitudinal ridges or ribs, is from small-scale vegetable farms near of 5 indicated minimum commercial ac- consumed much like summer squash. Ma- Davis and Stockton, California. They were ceptability.

CALIFORNIA AGRICULTURE, MARCH-APRIL 1993 27 Visual quality of bitter melon (A and B), fuzzy melon (C) and angled luffa (D) after storage at different temperatures for 14 days. Fruits were evaluated 3 days after transfer to 15°C (59°F).

28 CALIFORNIA AGRICULTURE, VOLUME 47, NUMBER 2 Yard-long bean 0 5°C tures. Changes in respiration rates at Storage of bitter melon, yard-long bean 180 A 7.5'C 160 0 10% 12.5"C (55°F) and 15°C (59°F) were associ- and angled luffa at temperatures below f 140 v 12.5"C ated with internal development. The con- 10°C (59°F) and fuzzy melon below 12.5"C 0 15°C p 120 tinuous gradual increases in respiration (55°F) resulted in severe chilling injury 3 100 0 80 rates at 5°C (41°F) and 7.5"C (45°F)indi- within 14 days. Nonchilling-related qual- - cated the onset of chilling injury. ity defects that occurred during storage :: These immature fruit vegetables pro- are summarized in table 4. 20 0' duced little ethylene (<0.1yl/kg-h at 20°C Yard-long beans are particularly prob- = 68°F) under normal conditions, but lematic to handle because of their high res- 60 4 Angled luff* showed increases in "stress" ethylene piration rate, high chilling sensitivity, and 50- Y when stored below 10°C (50°F).At higher high rates of water loss and seed develop- 3 40- temperatures (15°C = 59°F and 20°C = ment at nonchilling temperatures. Yard- 2 30- 68"F), yard-long beans, bitter melon and long beans are often iced commercially E 20 - angled luffa showed internal growth and marketed as quickly as possible. changes often associated with temporary These conditions may cause chilling injury 10 - increases in ethylene production. For bitter but greatly reduce deterioration due to 04 I I I I I I I melon, seed development was associated water loss. They will retain good quality 0 2 4 6 8 I01214 with other ripening-related changes, in- for up to 2 weeks if stored continuously at Days cluding external yellowing, internal red low temperatures, but they must be con- Fig. 1. Respiration rates (means and stan- dard deviations) of yard-long bean (top) color development, and longitudinal split- sumed immediately to avoid severe chill- and angled luffa (below)stored at 5°C ting of the fruit. Exposure of these veg- ing symptoms.Storing yard-long beans at (41OF), 7.5"C (45"F), 10°C (50"F), 12.5% etables to ethylene at 20°C (68°F) greatly 10°C (59°F)provides a shelf life of <1week. (55"F), and 15°C (59°F). accelerated ripening and decay. Effect of maturity at harvest Changes after storage Seed and fruit development after har- Respiration/ethylene production Yard-long beans, it was found, can be vest affected the overall quality of these Respiration rates are highly correlated stored successfully about 1 week, whereas fruit-type vegetables. Postharvest develop- with the degree of perishability of a har- angled luffa, bitter melon and fuzzy melon mental changes resulted in fruit splitting vested product. Changes in the respiratory can be stored for about 2 weeks at 10" to and ripening in bitter melon, pod swelling pattern after harvest are also associated 12.5"C (50" to 55°F). Quality evaluations in yard-long beans, thinning of the edible with changes in composition and other after transfer from storage temperatures to flesh and development of a sour flavor in qualities. Respiration rates of angled luffa, 15°C (59°F) showed the chilling-sensitive the fuzzy melon, and blossom-end en- bitter melon and fuzzy melon were mod- nature of these commodities.Data for largement, stem-end shrinkage and bitter erate (25 to 40 ml COJ kg-hat 20°C = fuzzy melon (fig. 2) and the appearance of flavor development in angled luffa. Bitter 68"F), and were comparable to those of bitter melon, luffa and fuzzy melon clearly melon fruits harvested at the immature or slicing cucumbers but lower than those of illustrate the effect of storage temperature green but fully developed (mature-green) summer squash. Respiration rates of yard- on final quality. The most common symp- stages were similar in quality when stored long beans were about four to five times toms of chilling injury and other at 7.5"C (45°F) and 10°C (50°F). Fully de- higher than those of the cucurbit fruit veg- postharvest defects (table 3) included veloped fruits stored at 12.5"C (55°F) and etables, but were similar to rates of a simi- brown or black surface discoloration, sur- 15°C (59"F), however, showed si&cantly lar product, snap beans. face pitting and sunken areas and high more green color loss, decay and fruit split- Figure 1 shows how the respiration rate levels of decay that began during storage ting than did fruits harvested immature. of yard-long beans and angled luffa and developed rapidly after transfer to changed during storage at five tempera- warmer conditions. Conclusions The vegetables bitter melon, angled luffa, fuzzy melon and yard-long beans are chilling sensitive and should not be stored below 10" to 12.5"C (50" to 55°F). Visual chilling symptoms were accentu- ated after transfer from storage tempera- tures to 15°C (59°F);they included pitted lesions, russeting, black and brown surface discolorations, and a high incidence of de- cay. Fruit development (seed develop- ment, color changes) continued during storage at temperatures >12.5"C (59°F). Respiration rates are high for yard-long bean, and moderate for fuzzy melon, bitter melon and angled luffa. These four fruit vegetables produce very little ethylene, but exposure to ethylene during post- harvest handling accelerates color changes and reduces quality. R. I. Zong is Postgraduate Researcher, M. I. Fig. 2. Visual quality (A), decay (B), black stain (C) and pitting (D) scores (means and stan- Cantwell is Extension Vegetable Specialist and dard deviations) of fuzzy melon stored at 7.5"C (45"F), 10°C (50"F), and 12.5% (55°F) for 12 L. L. Morris is Professor Emeritus, Depart- days. Fruits were evaluated 3 days after transfer to 15°C (59°F). ment of Vegetable Crops, UC Davis.

CALIFORNIA AGRICULTURE, MARCH-APRIL 1993 29