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Bruce D. Whitaker

Lipid composition and pigment content were determined in pericarp of `Pik Red' tomatoes (Lycopersicon esculentum Mill.) that were harvested when mature-green (MG) then ripened for 1 or 14 days at 20C, chilled for 11 or 21 days at 2C, or chilled for 21 days and transferred to 20C for 4 days (rewarmed). During ripening, chlorophyll fell below a detectable level, carotenes increased 100-fold, phospholipids (PLs) dropped ≈20%, and galactolipids (GLs) dropped ≈35%. Fatty-acid unsaturation decreased slightly. Steryl esters (SEs), more than free sterols (FSs) and steryl glycosides (SGs), increased at the expense of acylated steryl glycosides (ASGs), and in all four steryl lipids, the stigmasterol: sitosterol ratio rose dramatically, whereas the level of isofucosterol fell sharply. During chilling, chlorophyll declined ≈40% and carotenes ≈60%. PL content did not change, whereas GL fell ≈15%. Fatty-acid unsaturation increased slightly. FS, much more than SG and SE, increased at the expense of ASG. The stigmasterol: sitosterol ratio changed little in ASG, SG, and SE but declined in FS. Isofucosterol increased in FS and SE. Rewarming had little effect on the levels of chlorophyll, carotenes, or PL levels, but caused GL to fall another ≈15%. Fatty-acid unsaturation decreased slightly in GL and ASG. The distribution of total sterol in ASG, SG, FS, and SE changed dramatically, yielding proportions close to those in unchilled MG fruit. Also, 4 days after rewarming, the stigmasterol: sitosterol ratio had increased sharply, particularly in FS and SE, and there was a further rise in isofucosterol in all four steryl lipids. These results indicate that chloroplast damage occurs during chilling, but PL-rich cell membranes are not degraded, even upon rewarming. Changes in sterol composition and conjugation during chilling and after rewarming could result in membrane dysfunction.

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Mark G. Lefsrud and Dean A. Kopsell

Chlorophyll and carotenoid pigments were measured with high-performance liquid chromatography (HPLC) during leaf development in kale (Brassicaoleracea L. var. acephala D.C). Lutein and β-carotene are two plant-derived carotenoids that possess important human health properties. Diets high in these carotenoids are associated with a reduced risk of cancer, cataracts, and age-related macular degeneration. Kale plants were growth-chamber grown in nutrient solution culture at 20 °C under 500 μmol·m-2·s-1 of irradiance. Pigments were measured in young (<1 week), immature (1-2 weeks), mature (2-3 weeks), fully developed (3-4 weeks) and senescing (>4 weeks) leaves. Significant differences were measured for all four pigments during leaf development. Accumulation of the pigments followed a quadratic trend, with maximum accumulation occurring between the first and third week of leaf age. The highest concentrations of lutein were recorded in 1- to 2-week-old leaves at 15.1 mg per 100 g fresh weight. The remaining pigments reached maximum levels at 2-3 weeks, with β-carotene at 11.6 mg per 100 g, chlorophyll a at 251.4 mg per 100 g, and chlorophyll b at 56.9 mg per 100 g fresh weight. Identifying changes in carotenoid and chlorophyll accumulation over developmental stages in leaf tissues is applicable to “baby” leafy greens and traditional production practices for fresh markets.

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Marilyn Rivera-Hernández, Linda Wessel-Beaver, and José X. Chaparro

Squash and pumpkins (Cucurbita sp.) are important contributors of beta-carotene to the diet. Consumers of tropical pumpkin and butternut squash (both C. moschata Duchesne) prefer a deep orange mesocarp color. Color intensity is related to carotene content. Among the five domesticated Cucurbita species, C. moschata and C. argyrosperma Huber have a close relationship. In crosses between these two species, fertile F1 plants can be easily obtained when using C. argyrosperma as the female parent. This research studied the relationship between and within C. moschata and C. argyrosperma by sequencing three genes in the carotenoid biosynthesis pathway and generating gene trees. Genotypes used in the study differed in flesh color from very pale yellow to dark orange. In some cases, haplotypes were associated with a particular mesocarp color. Further study of these types of associations may improve our understanding of color development in Cucurbita. The frequency of single nucleotide polymorphisms (SNPs) in the sequenced fragments was low. There were more SNPs and more heterozygotes among C. moschata accessions than among C. argyrosperma accessions. Haplotypes of the outgroups (C. ficifolia C.D. Bouché and C. maxima Duchesne) were always distinct from C. moschata and C. argyrosperma. These later species had both distinct haplotypes and shared haplotypes. Haplotypes shared among species tended to be maintained in the same branch of the phylogenetic tree, suggesting either gene flow between the species or a common ancestral gene. Both explanations suggest a close genetic and evolutionary relationship between C. moschata and C. argyrosperma.

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Carl M. Jones and James R. Myers

Continued and mounting evidence of the health benefits provided by carotenoid and anthocyanin pigments has increased public interest in dietary sources of these important phytonutrients. Tomatoes (Lycopersicon esculentum) are the primary dietary contributor of lycopene and an important source of beta-carotene. A collection of tomatoes containing the genes hp-1, dg, ogc, Ip, B and Af that are known to affect carotenoid and anthocyanin levels have been analyzed using HPLC. Levels of lycopene, beta-carotene, phytoene, and phytofluene have been determined in these accessions. Accession LA 3005, containing the dg gene, had the highest lycopene levels of the accessions analyzed (14 mg/100 g fresh wt.). A rapid HPLC method for quantitation of carotenoid levels from tomato fruit has been developed. “Heirloom” black and purple tomatoes have also been included in the accessions analyzed and have carotenoid levels comparable to cultivated red tomatoes. Anthocyanin presence has been confirmed only in the accessions LA 1996 (Af) and in some fruit of segregating plants from LA 3668 (Abg). Total monomeric anthocyanin content of LA 1996 as measured by the pH differential method is estimated to be 5.6 mg/100 g in the outer pericarp tissues and 18.6 mg/100 g in the skin tissue.

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Simone Fanasca, Giuseppe Colla, Youssef Rouphael, Francesco Saccardo, Giuseppe Maiani, Eugenia Venneria, and Elena Azzini

A greenhouse experiment was carried out to determine the effect of cationic proportions (K, Ca, Mg) in the nutrient solution on carotenoids and α-tocopherol content at green–orange, orange, red, and intense-red ripening stages using a high-pigment tomato (Lycopersicon esculentum Mill.) cultivar hp (`Lunarossa') and a standard cultivar (`Corfù') grown in a soilless culture. The highest lycopene concentration was observed in the `hp' cultivar at the red and intense-red ripening stages (3.0 mg/100 g fresh weight and 3.2 mg/100 g fresh weight respectively). In both cultivars, the concentration of β-carotene increased during the ripening stages, reaching the highest value (0.6 mg/100 g fresh weight) at the intense-red stage. The hp cultivar has guaranteed higher lycopene (average, 2.0 mg/100 g fresh weight vs. 1.7 mg/100 g fresh weight) and α-tocopherol contents (average, 1.2 mg/100 g fresh weight vs. 0.9 mg/100 g fresh weight) than those of the standard. In both cultivars, a high proportion of K in the nutrient solution increased antioxidant concentration β-carotene and especially lycopene) during the red and intense-red ripening stages, followed by Mg. The lowest values were recorded for the Ca treatment. Lastly, a positive correlation was recorded between fruit tissue K and lycopene content, whereas a negative correlation was observed between fruit tissue Ca and lycopene content.

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Sergey Nesterenko and Kenneth C. Sink

Lutein and zeaxanthin are becoming established as carotenoids beneficial for protection against common age-associated eye diseases. Thus, 15 potato (Solanum tuberosum subsp. tuberosum L.) breeding lines, cultivars Atlantic, Spunta, and Yukon Gold; and orange flesh OR-4 were surveyed for carotenoid profiles. Seven carotenoids, including violaxanthin, neoaxanthin, antheraxanthin, lutein, zeaxanthin, β-cryptoaxanthin, and β-carotene, were identified in the 19 genotypes. Violaxanthin and lutein were the prominent carotenoids detected in all genotypes studied. Neoaxanthin and antheraxanthin were found in 26% and 63% of the genotypes, respectively. β-Cryptoaxanthin, zeaxanthin, and β-carotene were found in only 5%, 10%, and 16% of the genotypes, respectively. Lutein varied from 19.8 to 119.0 μg·100 g-1 fresh weight across the 15 white- or yellow-flesh breeding lines. In contrast, zeaxanthin was detected at a low level in only one breeding line and at high level in OR-4. The three cultivars had profiles typical of yellow-flesh potatoes `Spunta' and `Yukon Gold'; while `Atlantic' had a typical white-flesh profile and a trace of zeaxanthin. The carotenoid baseline data established in this study provide information for activities to enhance potato for lutein and zeaxanthin.

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Andrew Schofield* and Gopinadhan Paliyath

The accumulation of carotenoids such as lycopene and beta-carotene greatly influences the quality of ripe tomato (Lycopersicon esculentum) fruit because cellular levels of these compounds determine the intensity of red color. As well, lycopene has anti-cancer properties and beta-carotene is a Vitamin A precursor. Recent work has demonstrated phytochrome regulation of the carotenoid pathway but the mechanism is not completely understood. This work investigates phytochrome regulation of 1-deoxy-D-xylulose 5-phosphate synthase (DXS) and phytoene synthase (PSY), two key enzymes of carotenogenesis. A simple procedure for the assay of PSY from crude pericarp extracts was developed and mRNA levels of DXS and PSY1 genes were measured by relative RT-PCR. Discs from mature green tomatoes were ripened in total darkness, or in darkness interrupted by brief daily treatments of red light, or red light followed by far red light. After ten days of incubation, lycopene levels of red light-treated discs had reached ≈12 mg/100 g fresh weight; nearly a 50% increase over discs ripened in total darkness. This increase was not observed in discs treated with red light followed by far red light, demonstrating the red/far red reversibility (and thus phytochrome control) of carotenoid accumulation. Similar patterns of phytochrome control are observed for PSY activity but not for DXS and PSY1 transcript levels, suggesting the mechanism of control may be at the level of post-translational modification of PSY. Potential applications of this regulation of carotenoid accumulation will be discussed.

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Murshidul Hoque*, Husein Ajwa, and Beiquan Mou

Lettuce (Lactuca sativa L.) is an essential salad crop in the American diet. Nitrogen (N), phosphorus (P), and potassium (K) are required for successful lettuce production and can influence lettuce quality. The objective of the study was to evaluate changes in nutritional composition of romaine (`Green Tower') and iceberg (`Sharp Shooter') lettuce in responses to N, P and K fertilization during fall production in Salinas, Calif. Sixteen treatment combinations of fertilizer were selected to provide a range of treatments. N was applied at 0, 112, 225, and 338 kg·ha-1 as ammonium nitrate; P was applied at 0, 112, and 225 kg/ha as super phosphate; and K was applied at 0 and 112 kg·ha-1 as muriate of potash. Nutritional content of fresh tissue of two types of lettuce was analyzed using high performance liquid chromatography (HPLC). Among the parameters analyzed were lutein, beta-carotene, chlorophyll a, and chlorophyll b. Yield was increased with increasing N fertilizer level, but was not affected by P or K application rates. The best post harvest quality, however, was at moderate P application rate. Increasing the N and P rates gradually increased glucose content in lettuce but decreased the shelf life. Significant differences between the two types of lettuce were found in chlorophyll, lutein and beta-carotene content. No significant correlations were found between soil fertilizer application levels and nutritional content of lettuce. However, the ratio of chlorophyll a and b were greater with the increase of fertilizer rate. Nutritional composition including vitamin C will be presented.

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Shiow Y. Wang and Hongjun Jiao

The effect of blackberries (Rubus sp.) genotypes on antioxidant activities against superoxide radicals (O2 ), hydrogen peroxide (H2O2), hydroxyl radicals (OH), and singlet oxygen (O,), was evaluated. The results were expressed as percent inhibition of active oxygen species production in the presence of fruit juice. The active oxygen radical absorbance capacity (ORAC) value referred to the net protection in the presence of fruit juice, and was expressed as micromoles of α-tocopherol, ascorbate, α-tocopherol, and β-carotene equivalents per 10 g of fresh weight for O2 , H2O2, OH, and O2, respectively. Among the different cultivars, juice of Hull' blackberry had the highest oxygen species, superoxide radicals (O2 ), hydrogen peroxide (H2O2), hydroxyl radicals (OH), and singlet oxygen (O2,) scavenging capacity. Different antioxidants have their functional scavenging capacity against active oxygen species. There were interesting and marked differences among the different antioxidants in their abilities to inhibit the different active oxygen species. β-carotene had by far the highest scavenging activity against O2 but had absolutely no effect on H2O2. Ascorbic acid was the best at inhibiting H2O2 free radical activity. For OH, there was a wide range of scavenging capacities with α-tocopherol the highest and ascorbic acid the lowest. Glutathione had higher O2 scavenging capacity compared to the other antioxidants.

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Amy Simonne, Eric Simonne, Ronald Eitenmiller, and Christine Harris Coker

Lettuce (Lactuca sativa) production historically has been limited in the southeastern United States because of the risk of early bolting and unacceptable bitterness. Small-scale vegetable growers may be able to include lettuce in their production through selection of bolt tolerant and nonbitter varieties. The objectives of this research were to evaluate earliness, bitterness, vitamin E, ascorbic acid, folate, β-carotene, and lutein content in 17 lettuce varieties. Significant difference were found among varieties for days to harvest (DTH) (47 DTH for `Epic' to 37 DTH for `Big Curly'). Observed DTH in this study was consistently 7 to 10 days less than commercial descriptions of the lettuce varieties, due to the use of transplants. Only `Slobolt' and `Greengo' bolted before reaching marketable size. Panelists found that the bitterness was acceptable for most varieties, but not for `Nancy,' `Big Curly,' and `Slobolt'. Significant differences among varieties were also found in vitamin E, ascorbic acid, folate, β-carotene, and lutein. `Redprize' and `Nevada' were the best varieties overall, while `Salinas 88 Supreme,' `Epic,' `Legacy,' `Big Curly,' `Slobolt,' and `Greengo' were unacceptable.