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Kil Sun Yoo*, Julio Loaiza, Kevin Crosby, Leonard Pike, and Steve King

About 40 watermelon samples with various flesh colors (red, pink, orange, and yellow) were tested for their carotene, sugar, and ascorbic acid contents. Carotenoids were separated and purified by using a preparative HPLC system and identified by comparing the spectra with standard compounds by using a diode array detector. Sugar and ascorbic acid contents were measured by HPLC methods. Red and pink colored watermelon contained lycopene as the major carotenoid, with a wide range of variation (5 to 51 μg·g-1). Beta-carotene was the second major carotenoid and was less than 6 μg·g-1. There were also lutein and violazanthin in less than 1.5 μg·g-1 range. Yellow and orange flesh watermelons contained a complex mixture of carotenes. Prolycopene, lycopene, or beta-carotene was the major component, depending on the variety, and the contents were less than 24, 3, and 9 μg·g-1, respectively. There were also minor carotenoids, such as violaxanthin, lutein, neurosporene, zea-carotene with a 0 to 3.5 μg·g-1 range. Neurosporene, zea-carotene, and prolycopene were not found in the red watermelons. There was great variation in total sugar content, range being from 22 to 102 mg-1, while the °Brix was from 4.0 to 15.5. Sucrose, glucose, and fructose were the main sugars in the watermelon and their composition were grouped as sucrose-dominant or fructose-dominant groups. Some varieties with very low levels of sucrose were generally low in the total sugar content. Watermelon contained fairly low levels of ascorbic acid, less than 58 μg·g-1 and some varieties had nearly no ascorbic acid. Estimation of total carotenoid in the yellow watermelons by measuring absorbency at 435, 485, or 503 nm was tested and 435 nm showed the highest correlation coefficient (r 2 =0.845).

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Mark G. Lefsrud and Dean A. Kopsell

Controlled plant growing systems have consistently used the standard earth day as the radiation cycle for plant growth. However, the radiation cycle can be controlled using automated systems to regulate the exact amount of time plants are exposed to irradiation (and darkness). This experiment investigated the influence of different radiation cycle periods on plant growth and carotenoid accumulation in kale (Brassica oleracea L. var. acephala DC.). Plants were grown in a controlled environment using nutrient solutions under radiation cycle treatments of 2, 12, 24 and 48 hours, with 50% irradiance and 50% darkness during each cycle. The radiation cycles significantly affected kale fresh weight, dry weight, percent dry matter, and the accumulation of lutein, β-carotene, and chlorophyll a and b. Maximum fresh weight occurred under the 2-hour radiation cycle treatment, whereas maximum dry weight occurred under the 12-hour treatment. Maximum accumulation of lutein, β-carotene, and chlorophyll a occurred with the 12-hour radiation cycle at values of 14.5 mg/100 g, 13.1 mg/100 g, and 263.3 mg/100 g fresh weight respectively. Maximum fresh weight production of the kale was not linked to increases in chlorophyll, lutein, or β-carotene. Consumption of fruit and vegetable crops rich in lutein and β-carotene carotenoids is associated with reduced risk of cancers and aging eye diseases. Increased carotenoid concentrations in vegetable crops would therefore be expected to increase the value of these crops.

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Mark G. Lefsrud, Dean A. Kopsell, Robert M. Augé, and A.J. Both

Consumption of fruit and vegetable crops rich in lutein and β-carotene carotenoids is associated with reduced risk of cancers and aging eye diseases. Kale (Brassica oleracea L. var. acephala D.C.) ranks highest for lutein concentrations and is an excellent source of dietary carotenoids. Kale plants were grown under varied photoperiods to determine changes in the accumulation of fresh and dry biomass, chlorophyll a and b, and lutein and β-carotene carotenoids. The plants were cultured in a controlled environment using nutrient solutions under photoperiod treatments of 6, 12, 16, or 24 hours (continuous). Fresh and dry mass production increased linearly as photoperiod increased, reaching a maximum under the 24-hour photoperiod. Maximum accumulation of lutein, β-carotene, and chlorophyll b occurred under the 24-h photoperiod at 13.5, 10.4, and 58.6 mg/100 g fresh mass, respectively. However, maximum chlorophyll a (235.1 mg/100 g fresh mass) occurred under the 12-hour photoperiod. When β-carotene and lutein were measured on a dry mass basis, the maximum accumulation was shifted to the 16-hour photoperiod. An increase in photoperiod resulted in increased pigment accumulation, but maximum concentrations of pigments were not correlated with maximum biomass production.

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Dean A. Kopsell, Carl E. Sams, T. Casey Barickman, and Robert C. Morrow

blue wavelengths (455 to 470 nm) significantly increased sprouting broccoli ( Brassica oleacea var. italica ) microgreen shoot tissue β-carotene, violaxanthin, total xanthophyll cycle pigments, glucoraphanin, epiprogoitrin, aliphatic glucosinolates

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Mark G. Lefsrud, Dean A. Kopsell, David E. Kopsell, and Joanne Curran-Celentano

Crop plants are adversely affected by a variety of environmental factors, with air temperature being one of the most influential. Plants have developed a number of methods in the adaptation to air temperature variations. However, there is limited research to determine what impact air temperature has on the production of secondary plant compounds, such as carotenoid pigments. Kale (Brassica oleracea L.) and spinach (Spinacia oleracea L.) have high concentrations of lutein and β-carotene carotenoids. The objectives of this study were to determine the effects of different growing air temperatures on plant biomass production and the accumulation of elemental nutrients, lutein, β-carotene, and chlorophyll pigments in the leaves of kale and spinach. Plants were grown in nutrient solutions in growth chambers at air temperatures of 15, 20, 25, and 30 °C for `Winterbor' kale and 10, 15, 20, and 25 °C for `Melody' spinach. Maximum tissue lutein and β-carotene concentration occurred at 30 °C for kale and 10 °C for spinach. Highest carotenoid accumulations were 16.1 and 11.2 mg/100 g fresh mass for lutein and 13.0 and 10.9 mg/100 g fresh mass for β-carotene for the kale and spinach, respectively. Lutein and β-carotene concentration increased linearly with increasing air temperatures for kale, but the same pigments showed a linear decrease in concentration for increasing air temperatures for spinach. Quantifying the effects of air temperature on carotenoid accumulation in kale and spinach, expressed on a fresh mass basis, is important for growers producing these crops for fresh markets.

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Peter J. Mes*, James R. Myers, and Balz Frei

A nutritional study was initiated to determine which carotenoids found in tomato result in decreased lipid oxidation ex vivo. To compare the carotenoids in a human diet without the use of purified supplements, tomatoes expressing nonfunctional enzymes in the carotenoid pathway were used. Tomato lines carrying the genes t, B, ogc, Del, or r were grown to produce fruit containing with high levels of prolycopene, beta-carotene, lycopene, or delta-carotene respectively, or low total carotenoids in r. Juices were processed from these lines and used in a dietary intervention study. Plasma samples were drawn before and after consumption of each juice. These samples were subjected to a battery of tests to analyze the contribution of carotenoids to the total lipid antioxidant status. Results of these tests are discussed.

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Judith Zambrano and Willian Materano

Mango fruits (Mangifera indica L.) were harvested at the preclimacteric stage. Fruits were immersed in 38, 42, 46, 50, and 54°C heated water for 30, 60, and 45 min prior to storage at 5°C for 2, 4, or 6 weeks in carton boxes. After storage, they were kept at 20°C. Fruits were evaluated for pulp color, total soluble solids, titrable acidity, ß-carotene content, reducing sugars and visible symptoms of chilling injury. Heated water had no significant effect on pulp color parameters (lightness, hue, and chroma). Soluble solids concentration, ß-carotene content and reducing sugars were higher in heated than in nonheated fruit after ripening. The chilling index was three-fold lower in treated than nontreated fruit. During storage and after removal at 20°C, hot-water-treated fruits ripened faster than nontreated fruits. Results of this study indicate that mango tolerance to chilling temperatures may increase after prestorage heat treatments.

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J.O. Kuti

Flavonoid content and antioxidant activity in peel and pulp samples of four different cactus pear fruit varieties were investigated. Major cactus fruit flavonoids were quercetin, kaempferol, and isorhamnetin. Greater amount of quercetin was found in the pulp compared with the peel samples in all varieties examined. Both kaempferol and isorhamnetin were found in at least three of the varieties (Opuntia ficus-indica; O. lindheimeri; O. streptacantha) exclusively in the peel samples. Generally, pulp tissue samples of all the cactus fruit varieties contained greater ascorbic acid, glutathione, alpha-tocopherol and beta-carotene and antioxidant activities than the peel tissue samples. Total flavonoids correlated well with antioxidant activity (r 2 = 0.89). Ascorbic acid had the highest antioxidant activity, followed by glutathione, beta-carotene, and alpha-tocopherol on equimolar basis.

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Gene E. Lester, John L. Jifon, and D. J. Makus

Netted muskmelon [Cucumis melo L. (Reticulatus Group)] fruit quality (ascorbic acid, β-carotene, total free sugars, and soluble solids concentration (SSC)) is directly related to plant potassium (K) concentration during fruit growth and maturation. During reproductive development, soil K fertilization alone is often inadequate due to poor root uptake and competitive uptake inhibition from calcium and magnesium. Foliar applications of glycine-complexed K during muskmelon fruit development has been shown to improve fruit quality, however, the influence of organic-complexed K vs. an inorganic salt form has not been determined. This glasshouse study investigated the effects of two K sources: a glycine-complexed K (potassium metalosate, KM) and potassium chloride (KCl) (both containing 800 mg K/L) with or without a non-ionic surfactant (Silwet L-77) on melon quality. Orange-flesh muskmelon `Cruiser' was grown in a glasshouse and fertilized throughout the study with soil-applied N–P–K fertilizer. Starting at 3 to 5 d after fruit set, and up to 3 to 5 d before fruit maturity at full slip, entire plants were sprayed weekly, including the fruit, with KM or KCl with or without a surfactant. Fruit from plants receiving supplemental foliar K had significantly higher K concentrations in the edible middle mesocarp fruit tissue compared to control untreated fruit. Fruit from treated plants were also firmer, both externally and internally, than those from non-treated control plants. Increased fruit tissue firmness was accompanied by higher tissue pressure potentials of K treated plants vs. control. In general, K treated fruit had significantly higher SSC, total sugars, total ascorbic acid, and β-carotene than control fruit. Fall-grown fruit generally had higher SSC, total sugars, total ascorbic acid and β-carotene concentrations than spring-grown fruit regardless of K treatment. The effects of surfactant were not consistent but in general, addition of a surfactant tended to affect higher SSC and β-carotene concentrations.

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J.A. Kirkpatrick, J.B. Murphy, and T.E. Morelock

Interest in the health benefits of vegetables prompted an investigation of the levels of carotenoids in commercial varieties and UA breeding lines of spinach. Plant carotenoids perform a critical function as antioxidants, providing protection against a variety of reactive oxygen species generated primarily during photosynthesis. When ingested by humans, these compounds maintain their antioxidant activities and are receiving considerable attention in relation to multiple health benefits, including cancer prevention. While the best-known and most-studied carotenoid is beta-carotene, other carotenoids are now receiving attention due to their higher antioxidant activity compared to beta-carotene. Most dark-green leafy vegetables, such as spinach and kale, are relatively high in carotenoids, especially lutein. In this study, significant differences in average content of both lutein and beta-carotene were found between genetic lines of spinach. Some lines exhibited considerable variation between plants, while others were highly uniform. There was a very high correlation (r 2 = 0.96) between lutein content and betacarotene content. The significant difference between spinach lines suggests that improvement of general carotenoid antioxidants and lutein could be obtained through a breeding program.