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S. J. Kays

Abstract

The O2 and CO2 concentration between the shuck and shell and within the nut of individual pecans (Carya illinoensis (Wang.) K. Koch cv. Stuart) was monitored over a 4 week period from predehiscence to post-dehiscence. Internal O2 levels increased after dehiscence from initial concentrations of 16-17% to near that of the external environment after 3 weeks. Internal CO2 concentration, conversely, decreased substantially after dehiscence. Treatment of nuts over the same physiological stages of development with 2.5, 5.0, 10.0, 21.0 and 100% O2 had little effect on the induction and development of the kernel's normal pigmentation. Both high and low O2 levels did, however, produce some discoloration after 21 days of treatment. Changes in the internal nut O2 partial pressure are apparently not a significant factor in the induction and development of the normal complement of pecan kernel pigments during fruit maturation.

Free access

Yan Wang and S.J. Kays

Breeding sweetpotatoes [Ipomoea batatas (L.) Lam.] for improved flavor would be greatly facilitated by understanding the flavor chemistry of the crop. To ascertain the chemical composition of the aroma, an aroma extract of baked `Jewel' sweetpotatoes was obtained using a cold solvent trap system and analyzed by gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS) and gas chromatography olfactometry (GCO) using aroma extract dilution analysis (AEDA). GC with a flame ionization detector (GC-FID) revealed ≈60 compounds presented in the aroma extract, of which 48 were identified. Olfactory evaluation of the eluted compounds using GC with a thermal conductivity detector (GC-TCD) indicated the presence of 37 odor-active peaks in the aroma extract. Three compounds, phenylacetaldehyde (perfume), maltol (caramel), and methyl geranate (2,6-octadienoic acid, 3,7-dimethyl-, methyl ester) (sweet candy) possessed the highest flavor dilution (FD) values (1500) via AEDA. 2-Acetyl furan (baked potato), 2-pentyl furan (floral), 2-acetyl pyrrole (sweet, caramel), geraniol (sweet floral), and β-ionone (violet) had FD values of 1000. These compounds are thought to be the most potent odorants in baked `Jewel' sweetpotatoes. Additionally, 1,2,4-trimethyl benzene, 2-furmethanol, benzaldehyde, 5-methyl-2-furfural, linalool, isopulegone, n-decanal, 2,4-decadienal, octyl ketone, α-copaene, 4-decanolide, and one unidentified compound were also contributors to the aroma. There was not a character impact compound that comprised the basic baked sweetpotato aroma. The aroma appeared to be made up of a relatively complex mixture of compounds. Maillard and/or caramelization reactions, Strecker degradation of phenylalanine, lipid and carotenoid degradation, and the thermal release of glycosidically bound terpenes appear to be involved in the formation of the characteristic aroma of baked `Jewel' sweetpotatoes.

Full access

K.H.S. Peiris and S.J. Kays

Centella asiatica, the Asiatic pennywort, is an herbaceous perennial indigenous to the southeastern United States. In some Asian countries, it is valued as an important vegetable and is widely cultivated. In addition, it is considered an important medicinal herb due primarily to the pentacyclic phytochemical, asiaticoside, which effectively treats a variety of skin diseases. Information on the botany, photochemistry, medicinal, nutritional value, and cultivation of the crop is reviewed. This species may warrant preliminary field and consumer acceptance tests as a speciality vegetable in the United States.

Free access

W.J. McLaurin and S.J. Kays

Four high-yielding sweetpotato [Ipomoea batatas (L.) Lam.] cultivars displayed substantial leaf shedding, under typical field production conditions, that was not due to pathological or herbivory causes. Losses ranged from ≈ 45% to 60% of the total leaves formed by the normal harvest date during 2 years. There was a strong positive correlation between leaf shedding and the number of vines (r2 = 0.80) and nodes (r2 = 0.89) per plant. Likewise, positive correlations were found between leaf shedding and total dry weight (r2 = 0.67), root fresh weight (r2 = 0.65), root dry weight (r2 = 0.60), and vine dry weight (r2 = 0.68). Distinct differences were found among cultivars in dry-matter allocation within the plant. `Jewel' allocated a lower percentage of dry matter into vines and a higher percentage into storage roots. Estimated leaf dry matter losses due to leaf shedding ranged from 1.2 to 2.6 t·ha-1. High leaf losses appear to be closely related to vigorous vine growth and subsequent shading of older leaves but did not have a negative impact on storage root yield in the cultivars tested.

Free access

W.J. McLaurin and S.J. Kays

Under typical field production conditions, four high-yielding sweetpotato cultivars (Centennial, Jewel, Regal and Resisto) were found to lose substantial amounts of leaves due to natural senescense rather than pathological or herbivory causes. Leaf loss by the normal harvest date ranged from 46 to 63% of the total leaves formed in 1991 and 48 to 59% in 1992. There was a strong positive correlation between leaves lost and the number of vines (r2 = 0.80) and nodes (r2 = 0.89) per plant. Positive correlations were also found between leaf loss and total dry weight of the plant (r2 = 0.67). root fresh weight (r2 = 0.65). root dry weight (r2 = 0.60), and vine dry weight (r2 = 0.68). Distinct differences were found among cultivars in dry matter allocation within the plant. Of the cultivars tested, 'Jewel' allotted a lower percentage of dry matter into vines and a greater percentage into storage roots. Estimated leaf dry matter losses due to leaf shedding ranged from 1.2 to 2.6 MT·ha-1. Amount of leaf loss appeared to be closely related to vigorous vine growth and subsequent shading of older leaves, though leaf loss did not have a negative impact on storage root yield in the cultivars tested.

Open access

N. J. Natarella and S. J. Kays

Abstract

Postharvest life of cut Ranunculus asiaticus flowers was substantially extended with low temperature storage; 0° and 5°C were superior to higher temperatures. Extended storage duration, however, increased the rate at which floral senescence occurred upon removal from cold storage.

Open access

S. J. Kays and D. M. Wilson

Abstract

Substantial quantitative differences in kernel pigmentation of pecan (Carya illinoensis (Wang) K. Koch) were measured in 8 cultivars and 1 selection. These pecans exhibit a wide range in color stability with storage and reversibility of detrimental color changes using surface pH alteration. Major differences were found between genotypes in the positive benefit from storage in the unshelled versus the shelled state.

Open access

L. A. Chang and S. J. Kays

Abstract

Respiration of sweet potato roots was significantly depressed by low oxygen concentrations from 5 to 15% compared to 20% O2, but respiration at 2.5% O2 was high. Total sugar accumulated with low oxygen (2.5 and 5.0%) storage. Protopectin was low in roots stored at low O2 concentrations but water soluble pectin was not significantly affected. Physical parameters Ew and δf the storage roots were high when stored at low O2 concentrations. Ey and Ef were not significantly affected. Ew was correlated with total sugar (r = 0.79).

Open access

R. M. Beaudry and S. J. Kays

Abstract

Several environmental and physical factors affect the kinetics of ethylene release from (2-chloroethyDphosphonic acid and (2-chloroethyl)methylbis(phenylmethoxy)silane. Target surface chemistry exerted a strong influence on the evolution of ethylene from both compounds. Ethylene release from (2-chloroethyl)methylbis(phenylmethoxy) silane was slowed by glass and hydrophobic substances such as wax, surfactants in the spray solution, and high concentrations of the parent molecule, but not by epicuticular waxes on leaves. Ethylene evolution from (2-chloroethyl)phosphonic acid was inhibited by glass and high levels of epicuticular waxes. The rate of ethylene release from both compounds was positively correlated with temperature; however, ethylene released from (2-chloroethyl)methylbis(phenylmethoxy)silane was much less affected by temperature increases. Increases in light intensity promoted the initial release of ethylene from (2-chloroethyl)methylbis(phenylmethoxy)silane, but decreased long-term yield. Light intensity had no effect on the breakdown of (2-chloroethyl)phosphonic acid.

Open access

D. A. Smittle and S. J. Kays

Abstract

Mechanically harvested southernpeas (Vigna unguiculata (L.) Walp cv. Purple Hull Pink Eye lost substantial green color within 2 – 3 hours after harvest. Color loss was greater at higher temperature. Color changes were more closely related to O2, CO2, acetaldehyde and ethanol concentration in the load atmosphere than to endogenous ethylene concentrations. Solids and total sugar content decreased after harvest and were not affected by product temperature within the range studied. Flavor and off-flavor acceptability ratings were closely related to time from harvest, product temperature and load atmosphere O2 and CO2 concentrations, but were not closely associated with ethylene, acetaldehyde or ethanol concentrations.