The bioactive constituents and antioxidant activities of ten selected Brazilian Cerrado fruits

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This is the first study of the bioactive compounds of Rollinia mucosa, Alibertia verrucosa, and Buchenavia tomentosa.

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Brazilian native fruits are essential food sources for local people and possibly viable raw materials for new products.

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Brazilian Fruits from Cerrado contain bioactive compounds with high antioxidant potential in vitro, comparable to other well-known fruits.

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Mirindiba (Buchenavia tomentosa) contains above-average levels of tocopherol, carotenoids, vitamin C and total phenolic.

This study measured the total levels of phenolic, anthocyanin, carotenoid, and tocopherol compounds, and vitamin C in ten fruits from the Brazilian Cerrado: araçá-boi, bacaba, bacupari, biribá, cajuí, curriola, marmelada-espinho, mirindiba, murici, and puçá-preto. Five extracts were prepared from each fruit using solvents with different polarities. The Trolox equivalent antioxidant activity, oxygen radical absorbance capacity, and inhibition of β-carotene bleaching were determined for each extract. Scott-Knott test and principal component analysis showed that the analyzed fruits were rich sources of different classes of bioactive compounds, with levels comparable to those in commonly consumed fruits such as guavas, and various berries and citrus fruits. To our knowledge, this is the first comprehensive study of the bioactive compounds and antioxidant activities of biribá, cajuí, marmelada-espinho, and mirindiba. Moreover, mirindiba was found to be a rich source of vitamin C and phenolics, with an average level of carotenoids and tocopherols.

Emission of volatile organic compounds from yellow onion (Allium cepa L.) bulbs during storage

Fresh onions (Allium cepa L.) emit volatile organic compounds (VOCs) naturally in very low concentrations. The aim of the present study was to determine the emission rate of low-boiling VOCs from healthy and naturally infected onion bulbs at 4, 15, and 25 °C and to evaluate the applicability of the VOC method to monitor quality changes during 12 weeks of storage of two cultivars ('Hystand' and 'Hoza') of yellow onions. VOCs were extracted from the headspace of bulbs by solid phase micro-extraction (SPME) up to 5 times during storage and analyzed by gas chromatography-mass spectrometry (GC-MS). A total of twenty-nine compounds were measured and twenty-seven of these were identified while thirteen were reported for the first time from yellow onion bulbs. Acetone (0.10-18.0 nmol kg^-1 day^-1), dimethyl disulfide (0.12-18.9 nmol kg^-1 day^-1) and hexanal (0.05-4.40 nmol kg^-1 day^-1) were among the most abundant volatiles emitted from healthy bulbs. The concentration of these compounds as well as the total volatiles decreased with time in storage. However, microbial infection resulted in higher emission of propene, carbon disulfide, isoprene, pentane, 2-methylfuran, 3-methylfuran, 1-propenethiol, hexane, and methyl propyl sulfide, indicating that VOC emission may be used as an indicator to monitor natural senescence and decay of stored onion bulbs.

Online measurement of temperature and relative humidity as marker tools for quality changes in onion bulbs during storage

A long shelf life of onions (Allium cepa L.) is of high importance in the onion industry. Onions are dried and stored in large wooden boxes that are difficult to access. Monitoring temperature and relative humidity during these processes is challenging. Moreover, quality may change in storage without being noticed. Therefore, there is a need to find alternative methods for monitoring and controlling the drying and storage processes of onions and to identify early changes in quality during storage. The potential use of online measurements of temperature and relative humidity (RH) in the vicinity of onions was evaluated during drying and long-term storage of six onion batches (four cultivars and three selections of one of the cultivars) in commercial storage. The batches varied in bulb weight, dry matter content, firmness and disease incidence. The dry matter content and firmness decreased during storage, while the respiration rate and incidences of individual and total disease increased. Two of the batches had low storability with high disease incidences and high average temperatures and variations in the RH. The results showed that tracking the temperature and RH in the vicinity of the onions is a promising tool for improving the drying and storage processes in commercial storage and for identifying onion batches with reduced storability early in storage.

Noninvasive Determination of Firmness and Dry Matter Content of Stored Onion Bulbs Using Shortwave Infrared Imaging with Whole Spectra and Selected Wavelengths

A firm texture of dry onions is important for consumer acceptance. Both the texture and dry matter content decline during storage, influencing the market value of onions. The main goal of this study was to develop predictive models that in future might form the basis for automated sorting of onions for firmness and dry matter content in the industry. Hyperspectral scanning was conducted in reflectance mode for six commercial batches of onions that were monitored three times during storage. Mean spectra from the region of interest were extracted and partial least squares regression (PLSR) models were constructed. Feature wavelengths were identified using variable selection techniques resulting from interval partial least squares and recursive partial least squares analyses. The PLSR model for firmness gave a root mean square error of cross-validation (RMSECV) of 0.84 N, and a root mean square error of prediction (RMSEP) of 0.73 N, with coefficients of determination ( R²) of 0.72 and 0.83, respectively. The RMSECV and RMSEP of the PLSR model for dry matter content were 0.10% and 0.08%, respectively, with a R² of 0.58 and 0.79, respectively. The whole wavelength range and selected wavelengths showed nearly similar results for both dry matter content and firmness. The results obtained from this study clearly reveal that hyperspectral imaging of onion bulbs with selected wavelengths, coupled with chemometric modeling, can be used for the noninvasive determination of the firmness and dry matter content of stored onion bulbs.

Novel non-destructive quality assessment techniques of onion bulbs: a comparative study

This study was designed to compare the performances of four different non-destructive methods of assessing onion quality, one of which was based on near-infrared spectroscopy, and three of which were based on spectral imaging. These methods involve a combination of wavelengths from visible to near-infrared with different acquisition systems that were applied to discriminate between pre-sorted onions by in situ measurements of the onion surface. Compared with the partial least squares discriminant analysis classification models associated with different methods, hyperspectral imaging (HSI) with both static horizontal and rotating orientation obtained a higher level of sensitivity and specificity with a lower classification error than did other methods. Moreover, models built with the reduced variables did not lower the model performances. Overall, these results demonstrate that HSI with selected wavelengths would be useful for further developing an improved real-time system for sorting onion bulbs.

Eating Quality of Carrots (Daucus carota L.) Grown in One Conventional and Three Organic Cropping Systems over Three Years

The eating quality of carrots (Daucus carota L.) was investigated to evaluate the impact of cropping systems (one conventional and three organic systems) and growing years (2007, 2008, and 2009) on root size, chemical composition, and sensory quality. The content of dry matter, sugars, polyacetylenes, and terpenes as well as the sensory quality and root size were related to the climate during the three growing years. A higher global radiation and a higher temperature sum in 2009 as compared to 2007 and 2008 resulted in larger roots, higher contents of dry matter, sucrose, total sugars, and total polyacetylenes, and lower contents of terpenes, fructose, and glucose. No differences were found between conventional and organic carrots with regard to the investigated parameters. This result shows that organically grown carrots have the same eating quality as conventionally grown carrots, while being produced in a more sustainable way.

Culinary preparation of beetroot (Beta vulgaris L.): the impact on sensory quality and appropriateness

BACKGROUND

Beetroot is a diverse vegetable available in different shapes and colours. The objectives of this study were to evaluate sensory qualities, and sugar and dry matter content of five beetroot varieties in relationship to the appropriateness for raw, boiled and pan-fried preparation.

RESULTS

Sensory evaluation by descriptive sensory analysis and consumer tests showed clear distinctions between red varieties Taunus, Rocket and Pablo, and the pink-white striped Chioggia and yellow Burpee's Golden in raw preparations. However, variety delimination was more difficult after boiling and pan-frying. Different sensory qualities were important for beetroot appropriateness in raw, boiled and pan-fried preparations. Appropriateness of raw beetroots was associated with high sensory scores in beetroot flavour, crispness and juiciness, and low scores in bitterness. Appropriateness of boiled beetroots was related to high scores in beetroot and earthy flavours. Pan-fried beetroot appropriateness was associated with high scores in beetroot flavour, colour intensity and crispness.

CONCLUSION

This study showed that the quality of raw materials is integral in culinary preparations. These results can be used to guide consumers in the use of beetroot in culinary preparations and subsequently increase consumption.

Impact of mixtures of different fresh-cut fruits on respiration and ethylene production rates

Packaging and storage of fresh-cut fruits and vegetables are a challenging task, since fresh produce continue to respire and senesce after harvest and processing accelerates the physiological processes. The response on respiration and ethylene production rates of fresh produce to changes in O2 and CO2 concentrations and temperature has been extensively studied for whole fruits but literature is limited on processed and mixed fresh-cut fruits. This study aimed to investigate the effects of mixing various proportions of fresh-cut fruits (melon chunks, apple slices, and pineapples cubes) on respiration and ethylene production rates and to develop predictive models for modified atmosphere packaging. The experiment was designed according to a simplex lattice method and respiration and ethylene production rates were measured at 10 °C. Results showed that single component pineapple cubes, apple slices, and melon chunks, in this order, had significant constant coefficients (P = 0.05) and the greatest impact on respiration rate while the interactive binary and tertiary coefficients were insignificant. For ethylene production rates, single component apple slices, melon chunks, and pineapple cubes, and their 3-component mixtures, in this order, had significant constant coefficients (P = 0.05) while binary coefficients were insignificant. Mathematical models were developed and validated; the cubical model was the best to describe the influence of proportion of fruit on respiration and ethylene production rates, however, considering simplicity the linear part of the model is recommended to quantify respiration and ethylene production rates of mixed fresh-cut fruits.

PRACTICAL APPLICATION

This research helps to quantify the ethylene production and respiration rates of multicomponent mixed fresh-cut fruit, which then can be used for packaging design of fresh-cut produce.

Mapping the variation of the carrot metabolome using 1H NMR spectroscopy and consensus PCA

Genetic variation is the most influential factor for carrot (Daucus carota L.) composition. However, difference in metabolite content between carrot varieties has not been described by NMR, although primary metabolites are important for human health and sensory properties. The aim of the present study was to investigate the effect of genotype on carrot metabolite composition using a (1)H NMR-based metabolomics approach. After extraction using aqueous and organic solvents, 25 hydrophilic metabolites, β-carotene, sterols, triacylglycerols, and phospholipids were detected. Multiblock PCA showed that three principal components could be identified for classification of the five carrot varieties using different spectroscopic regions and the results of the two solvent extraction methods as blocks. The varieties were characterized by differences in carbohydrate, amino acid, nucleotide, fatty acid, sterol, and β-carotene contents. (1)H NMR spectroscopy coupled with multiblock data analysis was an efficient and useful tool to map the carrot metabolome and identify genetic differences between varieties.

Sensory quality and appropriateness of raw and boiled Jerusalem artichoke tubers (Helianthus tuberosus L.)

BACKGROUND

The aim of the present study was to investigate the sensory attributes, dry matter and sugar content of five varieties of Jerusalem artichoke tubers and their relation to the appropriateness of the tubers for raw and boiled preparation.

RESULTS

Sensory evaluation of raw and boiled Jerusalem artichoke tubers was performed by a trained sensory panel and a semi-trained consumer panel of 49 participants, who also evaluated the appropriateness of the tubers for raw and boiled preparation. The appropriateness of raw Jerusalem artichoke tubers was related to Jerusalem artichoke flavour, green nut flavour, sweetness and colour intensity, whereas the appropriateness of boiled tubers was related to celeriac aroma, sweet aroma, sweetness and colour intensity. In both preparations the variety Dwarf stood out from the others by being the least appropriate tuber.

CONCLUSION

A few sensory attributes can be used as predictors of the appropriateness of Jerusalem artichoke tubers for raw and boiled consumption. Knowledge on the quality of raw and boiled Jerusalem artichoke tubers can be used to inform consumers on the right choice of raw material and thereby increase the consumption of the vegetable.

Investigation of volatiles emitted from freshly cut onions (Allium cepa L.) by real time proton-transfer reaction-mass spectrometry (PTR-MS)

Volatile organic compounds (VOCs) in cut onions (Allium cepa L.) were continuously measured by PTR-MS during the first 120 min after cutting. The headspace composition changed rapidly due to the very reactive volatile sulfurous compounds emitted from onion tissue after cell disruption. Mass spectral signals corresponding to propanethial S-oxide (the lachrymatory factor) and breakdown products of this compound dominated 0–10 min after cutting. Subsequently, propanethiol and dipropyl disulfide predominantly appeared, together with traces of thiosulfinates. The concentrations of these compounds reached a maximum at 60 min after cutting. Propanethiol was present in highest concentrations and had an odor activity value 20 times higher than dipropyl disulfide. Thus, propanethiol is suggested to be the main source of the characteristic onion odor. Monitoring the rapid changes of VOCs in the headspace of cut onion necessitates a high time resolution, and PTR-MS is demonstrated to be a very suitable method for monitoring the headspace of freshly cut onions directly after cutting without extraction or pre-concentration.

Metabolomics reveals drastic compositional changes during overwintering of Jerusalem artichoke (Helianthus tuberosus L.) tubers

Metabolic changes were investigated in overwintering Jerusalem artichoke (Helianthus tuberosus L.) tubers using proton nuclear magnetic resonance ((1)H NMR) metabolomics. Three varieties were studied; as a result of overwintering, the amount of inulin was found to decrease in Jerusalem artichoke tubers. This was mainly due to its conversion to sucrose and, at the same time, formation of inulin with a lower degree of polymerization. Major effects on the concentration of citric acid, malic acid, γ-aminobutyric acid (GABA), and adenosine were also found. Intriguingly, malic acid concentration increased and citric acid concentration decreased. These changes, together with an increase in sucrose and GABA concentrations, were ascribed to mobilization of nutrients prior to sprouting, suggesting that malic acid and GABA serve as carbon and nitrogen sources during sprouting of Jerusalem artichokes.

The influence of the fungal pathogen Mycocentrospora acerina on the proteome and polyacetylenes and 6-methoxymellein in organic and conventionally cultivated carrots (Daucus carota) during post harvest storage

Many carrots are discarded during post harvest cold storage due to development of fungal infections, caused by, e.g., Mycocentrospora acerina (liquorice rot). We compared the susceptibility of carrots grown under conventional and organic agricultural practices. In one year, organically cultivated carrots showed 3× to 7× more symptoms than conventionally cultivated, when studying naturally occurring disease at 4 and 6 months, respectively. On the other hand, we have developed a bioassay for infection studies of M. acerina on carrots and observed that organic roots were more susceptible after one month of storage than conventional ones, but no differences were apparent after four or six months storage. Levels of polyacetylenes (falcarinol, falcarindiol and falcarindiol-3-acetate) did not change, whereas the isocoumarin phytoalexin (6-methoxymellein) accumulated in infected tissue as well as in healthy tissue opposite the infection. The proteomes of carrot and M. acerina were characterized, the intensity of 33 plant protein spots was significantly changed in infected roots including up regulation of defence and stress response proteins but also a decrease of proteins involved in energy metabolism. This combined metabolic and proteomic study indicates that roots respond to fungal infection through altered metabolism: simultaneous induction of 6-methoxymellein and synthesis of defence related proteins.

Chromatographic Determination of Changes in Pigments in Spinach (Spinacia oleracea L.) During Processing

The content of individual chlorophyll and carotenoid pigments is determined in three spinach varieties (Lorelei, Springfield, and Ballet) after processing. Raw spinach and spinach that is steam-blanched for 3, 9, or 15 min is stored frozen at -24 degrees C for 6 months. In addition, spinach is air-dried at 75 degrees C, packed in atmospheric air or nitrogen, and stored at ambient temperature for 6 months. Processing has a significant effect on the content of individual chlorophyll and carotenoid pigments; however, there are no differences between varieties in their content of total and individual pigments in raw, frozen spinach. Increasing blanching time resulted in decreased contents of chlorophyll a and b and increased contents of chlorophyll a' and b' and pheophytin a and b because of pheophytinization. Changes in the color because of pheophytinization are only detected after 15 min blanching. The carotenoid pigments are more stable than the chlorophyll pigments during blanching. (all-E)-Violaxanthin is significantly reduced, caused by degradation to other xanthophylls, such as neochrome, during blanching. There are no significant differences in the content of chlorophyll a and b of dried spinach and blanched, frozen spinach. Formation of chlorophyll a' and b', pheophytin a and b, and chlorophyll a-1 and b-1 is observed after drying. The content of pheophytin a and b is significantly lower in dried versus blanched frozen samples. In dried spinach that is stored in atmospheric air, the content of beta-carotene [599 mg/kg dry matter (DM)] is significantly lower compared with nitrogen (766 mg/kg DM), and the content of (all-E)-lutein is lower than in blanched frozen spinach. Neochrome is not detected in raw spinach but in steam-blanched and dried spinach. No differences are observed in the content of (all-E)-neoxanthin, (9'Z)-neoxanthin, (all-E)-violaxanthin, (all-E)-lutein epoxide, or neolutein A and B between spinach that is stored frozen after 3 min blanching and dried spinach.

Changes in volatile compounds of carrots (Daucus carota L.) during refrigerated and frozen storage

Carrots (Daucus carota L.) of cv. Bolero and cv. Carlo were processed into shreds and stored for up to 4 months at -24 degrees C (frozen storage), or the roots were stored for up to 4 months at 1 degrees C (refrigerated storage) followed by processing into shreds. Volatiles from the carrot shreds were collected by dynamic headspace technique and analyzed by GC-FID, GC-MS, GC-MS/MS, and GC-O to determine the volatile composition and aroma active components of carrots stored under different temperature conditions. A total of 52 compounds were quantified, of which mono- and sesquiterpenes accounted for approximately 99% of the total volatile mass. Major volatile compounds were (-)-alpha-pinene, beta-myrcene, (-)-limonene, (+)-limonene, (+)-sabinene, gamma-terpinene, p-cymene, terpinolene, beta-caryophyllene, alpha-humulene, and (E)- and (Z)-gamma-bisabolene. A considerable increase in the concentration of mono- and sesquiterpenes was observed during refrigerated storage, whereas the concentration of terpenoids was around the same level during frozen storage. GC-O revealed that the major volatiles together with (+)-alpha-pinene, (-)-beta-pinene, (+)-beta-pinene, 6-methyl-5-hepten-2-one, (-)-beta-bisabolene, beta-ionone, and myristicin had an odor sensation, which included notes of "carrot top", "terpene-like", "green", "earthy", "fruity", "citrus-like", "spicy", "woody", and "sweet".

Comparison of methods used for pre-concentrating small volumes of organic volatile solutions

Eight pre-concentration techniques were compared for their capacity to retain volatile and semi-volatile solutes during evaporation of solvent (dichloromethane). The 2-ml test-samples containing 0.2 ppm or 2 ppm (v/v) of volatile and semi-volatile solutes were concentrated to a final volume of 1 ml, 200 microl and 50 microl, respectively. When pre-concentrating to 50 microl, the highest recoveries for both the diluted (0.2 ppm) and concentrated (2 ppm) solutions were found by passive evaporation in a test tube at 22 degrees C. The pre-concentration time from 2 ml to 50 microl by this method was 19-20 h. Heating the test tube to 47 degrees C yielded lower recoveries in dilute samples, but the recoveries of concentrated samples were only slightly lower than the recoveries obtained by passive evaporation. The evaporation time was decreased to 1-2 h. The recoveries and the reproducibility of these methods were superior to the other pre-concentration methods tested. Loss of solute was apparently mainly caused by the fast vapour streams created when speeding up the process of evaporation by heating or by introducing a gas stream into the tube. This increased co-evaporation and thereby solute loss. The capacity of the methods to trap the escaping vapours and create a reflux determined the capacity of the methods to recover the solutes. The experiments demonstrated that more solute is lost during the pre-concentration of dilute samples compared to more concentrated solutions.

HPLC determination of chlorophyll and carotenoid pigments in processed green pea cultivars (Pisum sativum L.)

Chlorophyll and carotenoid pigments from six cultivars of processed green peas (Avola, Tristar, Rampart, Turon, Bella, and Greenshaft) were extracted with 100% acetone and analyzed by reversed-phase HPLC. A total of 17 pigments were identified in the pea cultivars including 8 xanthophylls ((all-E)-neoxanthin, (9'Z)-neoxanthin, (all-E)-violaxanthin, neochrome, (all-E)-lutein epoxide, (all-E)-lutein, neolutein B, neolutein A), 4 chlorophyll b related compounds (chlorophyll b derivative, chlorophyll b, chlorophyll b', and pheophytin b), 4 chlorophyll a related compounds (chlorophyll a derivative, chlorophyll a, chlorophyll a', and pheophytin a), and (all-E)-beta-carotene. The efficiency of different extraction procedures using 100% acetone showed that initial extraction followed by three reextractions without holding time between gave a higher extraction yield than no reextraction and 30 or 60 min holding time. All six cultivars contained the same pigments, but the concentration of each pigment varied significantly. On average of the two years, the chlorophyll a concentration varied from 4800 to 7300 microg/100 g fresh weight, the chlorophyll b concentration from 2100 to 2800 microg/100 g fresh weight, the (all-E)-lutein concentration from 1200 to 1900 microg/100 g fresh weight, and the (all-E)-beta-carotene concentration from 300 to 490 microg/100 g fresh weight in the processed pea cultivars. These differences in pigment concentration between the investigated cultivars are discussed in relation to maturity, product color and nutritional quality.

Quantitative analysis of aroma compounds in carrot (Daucus carota L.) cultivars by capillary gas chromatography using large-volume injection technique

Dynamic headspace sampling was used to collect aroma compounds from raw samples of four carrot (Daucus carota L.) cultivars (Brasilia, Duke, Fancy, and Cortez). The collected volatiles were analyzed by capillary GC-FID and GC-MS using large-volume cool on-column injection (LVI-COC). Of the 36 compounds identified, 6 had not been previously detected in carrots. Significant differences between the carrot cultivars were found for 31 of the identified volatiles as well as for total monoterpenes, sesquiterpenes, and total volatile content. Mono- and sesquiterpenes accounted for about 98% of the total volatile mass in all cultivars. LVI-COC injection was used to determine the loss of carrot volatiles during concentration of headspace samples under a stream of nitrogen. The loss among major monoterpenes in the concentrated samples varied from 16% for p-cymene to >40% for alpha-pinene as compared to nonconcentrated samples. The loss among high-boiling sesquiterpenes varied from not detectable (beta-caryophyllene, alpha-humulene, and caryophyllene oxide) to approximately 7% for (E)- and (Z)-gamma-bisabolene.