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  • Author or Editor: Nancy Jung Chen x
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Mesocarp softening during papaya (Carica papaya L.) ripening was impaired by heating at 42C for 30 min followed by 49C for 70 min, with areas of the flesh failing to soften. Disruption of the softening process varied with stage of ripeness and harvest date. The respiratory climacteric and ethylene production were higher and occurred 2 days sooner in the injured fruit than in the noninjured fruit that had been exposed to 49C for only 30 min. Skin degreening and internal carotenoid synthesis were unaffected by the heat treatments. Exposure of ripening fruit to either 42C for 4 hr or 38 to 42C for 1 hr followed by 3 hr at 22C resulted in the development of thermotolerance to exposure to the otherwise injurious heat treatment of 49C for 70 min. Four stainable polypeptide bands increased and seven declined in single-dimensional acrylamide gels following incubation of fruit at the nondamaging temperature of 38C for 2 hr. Three polypeptides showed marked increases when polysomal RNA was translated. These polypeptides had apparent molecular weights of 17, 18, and 70 kDa. Proteins with molecular weights of 46, 54, and 63 kDa had slight increases after heat treatment. The levels of these polypeptides peaked 2 hr after heat treatment and declined within 24 hr. The amount of these polypeptides in the unheated control varied with the batch of fruit. The concentration of three translated polypeptides, with apparent molecular weights of 26, 37, and 46 kDa, declined. Other polypeptides continued to be translated during and after holding papayas for 2 hr at 38C.

Free access

Abstract

Composition of yam bean (Pachyrrhizus erosis L. Urb) tubers stored at 22° and 12.5°C was monitored monthly for up to 5 months. A continual loss of moisture occurred in tubers at both storage temperatures—after 4 months tubers stored at 22° lost 14.5% of their original weight; those stored at 12.5° lost 9.6%. A higher respiration rate of 15 to 28 ml·kg–1·hr–1 occurred during the first 2 months of storage at 12.5°. This was nearly double the respiration rate of tubers stored at 22°. Ethylene was not detected at any time. There are a continual breakdown of starch in tubers. After 3 months, tubers stored at 12.5° had one-sixth the harvest content of starch. At 22°, starch declined to two-thirds the harvest content. The decline in starch content at 12.5° was related to an increase in total sugars in the tuber, particularly sucrose. The sucrose content of the tuber stored at 12.5° tripled over a 3-month period. Glucose and fructose levels declined over the same period irrespective of storage temperature. The results suggest a chilling response that led to a sweeter tuber. Titratable acidity was very low, as was total phenols, and both did not change after harvest.

Open Access

Abstract

Sequential changes in starch, sugars, organic acids, and headspace volatiles were determined on single soursop fruits from harvest to fruit breakdown. Sucrose increased 4-fold; maximum concentration occurred 3 days after harvest, then declined to 40% of the peak value. Fructose and glucose increased slowly to a peak 5 days after harvest. The ratio of sucrose, glucose, and fructose, respectively, at the edible ripe stage was 4.3:3.0:3.2. There was a 7-fold increase in malic acid and a 3-fold increase in citric acid. Both acids peaked 3 to 4 days after harvest, then declined. About half of the organic acids were present as salts. Headspace volatile production paralleled ethylene evolution. Volatile production began to increase 3 days after harvest and peaked 2 days later. This peak corresponded with the peaks in total sugars, organic acids, and the edible ripe stage when individual fruit results were compared on the basis of the start of the climacteric respiratory increase. After the peak in volatile production, there was a dramatic drop over the next 3 days in major fruity esters produced, with a gradual increase in volatiles, which probably imparted the off-odor of the overripe fruit. The activities of amylase, polygalacturonase, and cellulase increased during ripening. Starch breakdown leading to sugar and organic acid production occurred before any rise in ethylene production. This breakdown of starch may be an important initiating event in the ripening of soursop fruit.

Open Access

Abstract

Physiological changes accompanying anthurium flower (Anthurium andraenum Andre) senescence were monitored. Silver pulse treatment of flower stems was used to modify the senescence process. Florets on the spadix continued to open for 5-10 days after harvest. In both treated and untreated flowers, respiration rate was low until senescence began 8 days after harvest. The rate of increase in respiration of silver treated flowers was half that of the controls. Ethylene production remained low throughout the postharvest life of the flowers. Ten days from harvest spathe color began to change from red to blue with no significant changes in the ratios of the anthocyanins. There was a simultaneous change in tissue pH, from 5.2 to 5.6. Tissue organic acids remained constant during senescence. There was a significant increase in spathe tissue ammonium ion due, apparently, to protein breakdown which probably caused the increase in tissue pH. The concentration of tissue phenolics increased during senescence and could have intensified the color change by copigmentation. Flower senescence apparently was not due to a shortage of carbohydrates, though tissue starch levels did decline by about 25%. The ratio of free sugars in the stem, spathe and spadix remained constant with a slight decline in concentration during postharvest life. Senescence probably was caused by water stress due to stem plugging of undetermined nature. Silver-pulsing of the stem reduced the amount of plugging and therefore reduced the rate of change of all the senescence processes.

Open Access

Abstract

Plant growth and tuberous root development in yam beans (Pachyrrhizus erosus L. Urb) were investigated using a series of 2-week plantings from April to December. Decreasing daylength at time of planting initiated tuberous root development, whereas increasing daylength inhibited tuberous root development and promoted vine and leaf growth. Once tuberous root formation and flowering began, stem and leaf growth ceased. At the time of planting, the critical daylength for tuberous root formation and flowering was 11 to 12 hr. The optimum planting date in Hawaii for maximum tuber yield of 24 t·ha–1 for yam beans was found to be September to October. Tuberous root development was sigmoidal, with dry matter percentage declining from 17.5% to 9%. There was little change in tuberous root acidity or total sugars during growth. Titratable acidity was about 20 meq·g–1 fresh weight if not induced to form tuberous roots, and ≈15 meq·g–1 fresh weight in plants forming tuberous roots. Total sugar was in the range of 30 to 50 mg·g–1 fresh weight during tuberous root growth of induced plants. Total phenols in the tuberous root declined during development, whereas roots from plants uninduced to form tuberous roots had an increased level of total phenols.

Open Access

The sugar-to-acid ratio of pineapple (Ananas comosus L.) contributes toward giving the fruit its unique flavor. This ratio is an important indicator of both commercial and organoleptic ripeness, and it is useful in determining a harvest date. Citric acid is the major acid in pineapple and usually is determined by titration to a specific pH endpoint, while sugars are determined as total soluble solids by refractometry. Both acid and sugar levels vary with the season in the year-round production cycle. Acid titration is slow and difficult to perform in the field. A digital acidity meter based upon diluted juice conductivity was evaluated for potential field use. The readings obtained from the meter varied with clone and fruit potassium concentration. The meter had utility for field use to evaluate fruit quality and harvest date. Because fruit potassium levels can vary between harvests, the meter should be recalibrated on a regular schedule to adjust for potential crop management and seasonal effects.

Open Access

Abstract

Methods were investigated to control weight loss and sprouting of stored ginger rhizome (Zingiber officinale Rosc), including waxing, sprout inhibitors, and gamma irradiation. Rhizomes stored for 3 months at 22°C and 70% RH lost about 20% weight. Waxing of the rhizome did not reduce water loss. Some wax treatments increased the number and length of sprouts. Preharvest application of maleic hydrazide significantly increased the number and reduced the length of sprouts. Postharvest CIPC application significantly reduced the length of sprouts. Vacuum infiltration increased the effectiveness of CIPC in reducing sprout length. Gamma and X-ray irradiation also reduced sprout number and length. Minimum doses of gamma radiation for sprout control was 25 Gy and 120 to 150 Gy for X-ray irradiation if the rhizome was stored for more than 3 months at 22°. A higher dose of irradiation (500 Gy) was required if complete sprout growth control was needed for storage periods <3 months at 22°. Suberization occurred during curing at 22°, but the suberin layer did not completely protect the cut surface. Chemical name used: isopropyl n-(3 chlorophenyl)-carbamate (CIPC).

Open Access

Abstract

Compositional changes in ginger (Zingiber officinale Rosc.) rhizome stored at 22° or 12.5°C were studied. The rhizome surface Hunter “b” value increased from 9.2 to 18 in 4 weeks. Water loss did not become significant until 12 weeks of storage at 22°. There was little increase in dry matter of rhizomes stored at 12.5°. Rhizome crude fiber content, oil percentage, total phenols, and protein content did not change significantly. Rhizome total sugar increased significantly during storage at 12.5° for 32 weeks with pungency increasing 5-fold, as measured by gingerol content. No significant volatile flavor changes were noted, with rhizome variation being greater than storage effect. The changes in rhizome surface color did not lead to a significant loss in quality. The increase in pungency could be regarded as a favorable improvement in the fresh ginger market. The loss of water and increase in dry matter percentage significantly decrease overall appearance and quality of rhizomes stored at 22°.

Open Access

Abstract

The changes in litchi (Litchi chinensis Sonn.) growth and composition were studied in 4 cultivars; ‘Groff’ in Hawaii, and ‘Shui Dong’, ‘Gui Wei’, and ‘Mei selection’ in Guangdong, China. Fruit and aril growth showed a sigmoidal pattern while skin growth was slower and more linear. Aborted seeds in Groff and Gui Wei ceased growth early in the log growth phase. Normal seeded cultivars showed seed growth paralleling skin growth. Skin chlorophyll began to decrease logarithmically soon after the start of fruit growth increase, with anthocyanin production beginning about halfway through the growth period. During the rapid growth period, due principally to an increase in aril tissue, there was an increase in total sugars from 3% to 16%. The cultivars showed slightly different ratios of the 3 sugars identified: sucrose, glucose, and fructose. Titratable acidity was due mainly to succinic and malic acid. This acidity decreased over 2 weeks in the middle of the fruit growth period from 65 meq/100 g to 15 meq/100 g. Succinic acid decreased in the same period from about 350 meq/100 g to 0.4 meq/100 g and remained low for the remaining 40 days of development. Malic acid declined from 75 meq/100 g to 12 meq/100 g, and citric acid remained constant at around 3 meq/100 g. A major portion of the decline in succinic acid was due to dilution. Total phenols were low throughout the growth of the fruit. Mineral uptake into the fruit paralleled fruit growth, with potassium being the major cation.

Open Access