Andrea Mahn

An overview of health-promoting compounds of broccoli (Brassica oleracea var. italica) and the effect of processing

Broccoli offers many heath-promoting properties owing to its content of antioxidant and anticarcinogenic compounds. The concentration and bioavailability of polyphenols, glucosinolates, sulforaphane and selenium depend on plant biochemistry, cultivation strategy and type of processing. In this article, the main biochemical properties of broccoli are reviewed regarding their health-promoting effects. Additionally, the way these properties are affected by processing is discussed. Steaming and drying result in an apparent increment of sulforaphane content as well as antioxidant activity, most likely due to an increase of the extractability of antioxidants and sulforaphane. Freezing and boiling diminish polyphenols concentration, mainly due to volatilization and leaching into the cooking water. In view of these results, the optimization of broccoli processing in order to maximize the content of bioactive compounds should be possible. The effect of processing on selenium compounds has been poorly studied so far, and therefore this topic should be investigated in the future. Finally, the effect of operating conditions in different drying processes on the content of bioactive compounds in broccoli should be investigated in a greater depth.

Analysis of the Drying of Broccoli Florets in a Fluidized Pulsed Bed

The effect of air temperature and flow rate, plate rotational speed, and initial broccoli particle size in a fluidized pulsed bed dryer on moisture content, diffusivity, antioxidant capacity, polyphenols content, and selenium concentration of conventional and selenium-enriched broccoli was investigated. Adjustment of the drying curves with the simplified constant diffusivity model was performed by intervals, in order to consider shrinkage, resulting in an average diffusivity equal to 4.9 E-09 (m2/s), which is 82% higher than that observed in drying of broccoli in a tunnel dryer. In addition, the drying curves were adjusted to Pages model, resulting in R 2 values higher than 0.9. The conditions that maximize the antioxidant properties of conventional broccoli florets were air temperature of 60°C, air flow rate in the dryer inlet of 3 m/s, and initial particle size of 1 cm. The disk rotational speed had no statistically significant effect on the antioxidant properties in the range from 60 to 100 rpm. These operating conditions were then used to dehydrate selenium-enriched broccoli. The antioxidant properties in selenium-enriched broccoli after drying were comparable to those obtained for conventional broccoli. The conditions that minimized selenium loss were air temperature of 53°C and air flow rate of 2 m/s.

Drying of Apple Slices in Atmospheric and Vacuum Freeze Dryer

Atmospheric freeze drying (AFD) and vacuum freeze drying (VFD) of Fuji apples was investigated. A factorial design was used in each case, with particle size, freezing rate, infrared (IR) radiation, and air temperature as factors. The effect of these factors on moisture content, duration of drying, rehydration properties, color, and texture were determined. The drying curves were fitted with both the simplified constant diffusivity model (SCDM) and the modified Page model, and rehydration curves were tested with the Peleg model, resulting in R2 higher than 0.96. Antioxidant capacity, polyphenols, and ascorbic acid content in the final product were determined and compared with those obtained in a tunnel dryer. A sensory evaluation was performed. The drying times obtained for VFD were shorter than the drying times obtained for AFD. The particle size and IR application were found to be the significant parameters that affect duration of drying for both AFD and VFD (duration of drying was proportional to particle size and inversely proportional to IR application). Air temperature affected drying time only during the secondary drying stage. Estimated Deff values were on the order of 10−10 (m2/s). In AFD, R2 higher than 0.81 was obtained for the SCDM, and R2 higher than 0.96 was obtained for the Page model. In VFD, a better fit was obtained (R2 > 0.97) for both models. AFD produced nutritional alterations similar to convective drying. Sensory quality was not altered by AFD or VFD.

Dietary supplementation with selenomethylselenocysteine produces a differential proteomic response

Organic forms of selenium offer important health benefits including cancer prevention. Selenium intake has been traditionally quantified as glutathioneperoxidase activity or selenium concentration in blood or tissues. However, these indexes do not reflect organic selenium intake. Effect of dietary supplementation of rats with selenomethylselenocysteine on the blood plasma proteome was investigated in order to detect protein abundance differences between experimental (supranutritional selenium supplementation) and control [minimum selenium dose and sodium selenate instead of selenomethylselenocysteine (SeMSeCys)] groups. Four experimental groups and six control groups consisting of six rats each were fed with base diet supplemented with SeMSeCys or sodium selenate in different concentrations for different periods of time. A proteomic approach, comprising two-dimensional gel electrophoresis and mass spectrometry, was used to assess protein abundance in blood plasma. Statistically significant differences in the abundance of some proteins were detected in all the experimental groups. Four proteins were found to increase their abundance in response to the experimental conditions: apolipoprotein E, haptoglobin and alpha-1-antitrypsin abundance was related to the extent of supplementation period and transthyretin in response to SeMSeCys dose. Apolipoprotein E and transthyretin were not differentially expressed when diets were supplemented with sodium selenate instead of SeMSeCys. We postulate that these proteins are potential biomarkers of chemoprotective selenium intake.

Effect of operating conditions in freeze-drying on the nutritional properties of blueberries

The effect of particle size, use of infrared radiation, and type of freeze-drying (vacuum or atmospheric) on some nutritional properties of blueberries was investigated. Ascorbic acid was decreased in freeze-dried blueberries compared with fresh fruit, while polyphenols were decreased in atmospheric freeze-drying—unlike in vacuum freeze-drying, where this nutritional property was increased. Antioxidant activity of freeze-dried blueberries did not differ significantly from that found in fresh fruits. In order to minimize the impairment of the nutritional properties of freeze-dried blueberries, it is suggested to use infrared radiation, a relatively small particle size and vacuum freeze-drying.

Effect of methyl jasmonate, sodium selenate and chitosan as exogenous elicitors on the phenolic compounds profile of broccoli sprouts.

BACKGROUNDnBroccoli sprouts are a good source of secondary metabolites, exhibiting biological activity, such as polyphenols, whose concentration is affected by the exposure to exogenous elicitors. The aim of this work was to investigate the effect of sodium selenate, chitosan and methyl jasmonate, applied directly to the seeds or through irrigation, on the content and profile of phenolic compounds in broccoli sprouts. The effect on antioxidant activity was also investigated.nnnRESULTSnMethyl jasmonate and chitosan decreased antioxidant capacity. Methyl jasmonate significantly decreased total polyphenols content in comparison with control sprouts, while chitosan significantly increased it. Sodium selenate had no statistical effect on antioxidant capacity and total polyphenols concentration. The polyphenols profile in sprouts was composed by quercetin, morine, genisteine, luteoline and sinapic acid. Elicitor type and concentration affected the synthesis of these compounds. Chitosan stimulated the synthesis of quercetin, sinapic acid and morine, whereas methyl jasmonate stimulated the synthesis of luteoline. Sodium selenate had no effect on polyphenols synthesis.nnnCONCLUSIONnThe exposure of broccoli to the elicitors produced changes in the phenolic compounds profile of broccoli sprouts. Besides, the stimulation of phenolic compounds synthesis was elicitor-specific, thus opening the possibility of managing culture conditions to increase the content of a specific phenolic compound.

Theoretical and experimental study of freeze-drying of "loco" (concholepas concholepas)

The “loco” is a mollusk somewhat similar to abalone that exists exclusively in Chile and Peru. Given the high commercial value of loco, preservation through freeze-drying seems economically viable. In this work, the freeze-drying process of loco meat was analyzed theoretically and experimentally. The effects of particle size, freeze-drying pressure, and intermittent use or not of microwave in the secondary drying stage, on the extent of the freeze-drying period, rehydration properties, shrinkage and texture were investigated by using a 23 factorial design. Drying and rehydration kinetics were adjusted to phenomenological models in order to determine mass transfer parameters. Freeze-drying pressure significantly affects the extent of the drying process. Freeze-drying pressure results in shrinkage, while microwave produces a volume increase. The effective moisture diffusivity (Deff) estimated form drying curves fluctuated between 10−10 and 10−11 (m2/s), agreeing with values reported for other meat products. The adjustment of the rehydration kinetics to the Constant Diffusivity Model gave the best fit, resulting in Deff in the order of 10−10 (m2/s). Particle size and freeze-drying pressure significantly affected rehydration capacity.

Organic and inorganic selenium compounds produce different protein patterns in the blood plasma of rats

Some selenium compounds offer important health benefits when administered at supranutritional doses, such as improvement of the immune system and of male fertility, and the prevention of some types of cancer. The traditional selenium indexes do not account for the metabolic status of this element among replete individuals. As a consequence, there is a need for new indexes that distinguish between repletion statuses of selenium. The aim of this work was to identify some plasmatic proteins that respond to supranutritional doses of selenium, which could be proposed as new protein markers of selenium intake. The effect on rats of dietary supplementation with either selenomethylselenocysteine (SMSeC) or sodium-selenate on some blood plasma proteins was investigated. Two experimental groups consisting of six rats each were fed a basic diet supplemented with either SMSeC or sodium-selenate at 1.9 microg-Se / g-diet for ten weeks. The control group was fed a diet that contained the recommended selenium dose (0.15 microg-Se / g-diet). The changes in the abundance of a group of plasmatic proteins were quantified and analysed statistically. Haptoglobin, apolipoprotein E and transthyretin increased their abundance after diet supplementation with either form of selenium. HNF6 was responsive only to SMSeC, whereas fibrinogen responded only to sodium-selenate. We postulate that the protein patterns observed in this work could be proposed as new molecular biology-based markers of selenium intake.

Modelling of the effect of selenium fertilization on the content of bioactive compounds in broccoli heads

Selenium (Se) exerts many effects beneficial to health. Broccoli is a Se-hyperaccumulator plant, with Se-fertilization increasing its potential as a functional food. We studied the effect of dose, and the developmental stage at the beginning of Se-fortification, on antioxidant capacity, phenolics, glucosinolates, sulphoraphane, Se-methyl selenocysteine and myrosinase in broccoli. Se-fortification decreased the antioxidant properties and sulphur-containing compounds, but increased Se-methyl-selenocysteine content. Regression models gave r>0.77 confirming that Se dose and developmental stage largely determine the behaviour of the system. Correlation models gave r>0.95, allowing estimation of saturation concentration of Se-methyl-selenocysteine in broccoli cv. Traditional (3.13µmolg-1DM) and the concentration (2-mmol sodium selenate) above which the content of phenolic compounds decreases significantly. Sulphoraphane and glucosinolates dependence on total Se supply was consistent with myrosinase activity below 3.5-mmol sodium selenate. Our results would enable design of optimal fertilization strategies to enrich broccoli in Se with minimal impairment of antioxidants properties.

Effect of Freeze-Drying Conditions on Antioxidant Compounds of Broccoli

The effect freeze-drying conditions, i.e. particle size, use of infrared radiation, and drying air temperature in Atmospheric Freeze-Drying (AFD) or freezing rate in vacuum Freeze-Drying (VFD) on the total selenium content, total polyphenols content and anti-radical power of broccoli was investigated. Two factorial designs were used, with three factors in two levels each one, for each type of freeze-drying. In AFD, the experimental factors were drying air temperature (5°C or 15°C), particle size (1.0 or 1.5 cm equivalent diameter), and use of infrared radiation (IR; yes or no). In VFD, the factors were freezing rate (high: by immersion in liquid nitrogen, low: in a household freezer at -30°C during 24 h), particle size and IR use, in the same levels as for AFD. In AFD, all experimental factors significantly affected the antioxidant properties of broccoli, while in VFD only the total polyphenols content was affected by freezing rate. Both AFD and VFD impaired antioxidant properties of the processed vegetable to different extents; however the content of total polyphenols and Se were considerably higher in broccoli subjected to AFD. Then AFD is an attractive alternative for broccoli preservation since it allows keeping some healthy properties of the vegetable. Finally, this technology seems promising in the functional food industry considering broccoli as raw material for this use.