Christof B. Steingass

Influence of chromoplast morphology on carotenoid bioaccessibility of carrot, mango, papaya, and tomato

Based on the observation of outstanding dissimilarities of the morphology of pigment-containing chromoplasts in nutritionally important carotenoid sources, the bioaccessibility (BA) of carotenoids from edible portions of carrot, mango, papaya, and tomato was compared using an in vitro digestion model. While carrot and tomato contained large carotenoid crystals clearly visible by light microscopy, mango and papaya contained different types of carotenoid-bearing structures. Particularly, β-carotene is deposited in globular and tubular elements in papaya and mango chromoplasts, where carotenoids accumulate in a lipid-dissolved and liquid-crystalline form, respectively. The highest BA of β-carotene was found for mango (10.1%), followed by papaya (5.3%), tomato (3.1%), and carrot (0.5%). In our digestion model, differences between total lycopene BA from papaya and tomato were insignificant, possibly since both pigments occur in a solid crystalline deposition form in both fruits. Furthermore, the BA of lutein, β-cryptoxanthin, and β-cryptoxanthin esters was shown to be superior to that of the carotenes from the respective food sources. The effect of lipid addition to the different food sources was studied. Although BA was enhanced for most carotenoids, the above-mentioned ranking of BAs of β-carotene remained unchanged after lipid addition. Consequently, the physical form of carotenoid deposition in plant chromoplasts is suggested to have major impact on their liberation efficiency from the food matrices.

Characterization of chromoplasts and carotenoids of red- and yellow-fleshed papaya (Carica papaya L.).

Chromoplast morphology and ultrastructure of red- and yellow-fleshed papaya (Carica papaya L.) were investigated by light and transmission electron microscopy. Carotenoid analyses by LC–MS revealed striking similarity of nutritionally relevant carotenoid profiles in both the red and yellow varieties. However, while yellow fruits contained only trace amounts of lycopene, the latter was found to be predominant in red papaya (51% of total carotenoids). Comparison of the pigment-loaded chromoplast ultrastructures disclosed tubular plastids to be abundant in yellow papaya, whereas larger crystalloid substructures characterized most frequent red papaya chromoplasts. Exclusively existent in red papaya, such crystalloid structures were associated with lycopene accumulation. Non-globular carotenoid deposition was derived from simple solubility calculations based on carotenoid and lipid contents of the differently colored fruit pulps. Since the physical state of carotenoid deposition may be decisive regarding their bioavailability, chromoplasts from lycopene-rich tomato fruit (Lycopersicon esculentum L.) were also assessed and compared to red papaya. Besides interesting analogies, various distinctions were ascertained resulting in the prediction of enhanced lycopene bioavailability from red papaya. In addition, the developmental pathway of red papaya chromoplasts was investigated during fruit ripening and carotenogenesis. In the early maturation stage of white-fleshed papaya, undifferentiated proplastids and globular plastids were predominant, corresponding to incipient carotenoid biosynthesis. Since intermediate plastids, e.g., amyloplasts or chloroplasts, were absent, chromoplasts are likely to emerge directly from proplastids.

Chemical and Morphological Characterization of Costa Rican Papaya (Carica papaya L.) Hybrids and Lines with Particular Focus on Their Genuine Carotenoid Profiles

Papaya (Carica papaya L.) F1 hybrids and inbred lines grown in Costa Rica were screened for morphological and nutritionally relevant fruit traits. The qualitative composition of carotenoids showed great similarity, being mostly composed of free and esterified β-cryptoxanthins accompanied by β-carotene, lycopene, and biosynthetic precursors. High levels of (all-E)-lycopene and its isomers were distinctive for red-fleshed hybrids, whereas yellow-fleshed fruits were virtually devoid of lycopenes. Because carotenoid levels among the investigated hybrids and lines differed significantly, this study supports the hypothesis of an exploitable genetic variability, and a potential heterotic effect regarding carotenoid expression may be instrumental in papaya-breeding programs. Due to significantly higher levels of provitamin A carotenoids and coinciding high levels of total lycopene, particularly red-fleshed hybrids might represent prospective sources of these compounds. Furthermore, the nutritional value of some genotypes was boosted by substantial amounts of ascorbic acid (up to 73 mg/100 g of fresh weight), which correlated to total soluble solids (R(2) = 0.86).

Influence of harvest maturity and fruit logistics on pineapple (Ananas comosus [L.] Merr.) volatiles assessed by headspace solid phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC/MS).

Profiling of volatiles from pineapple fruits was performed at four ripening stages using headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC/MS). In total, 142 volatiles were detected, of which 132 were identified. Multivariate data analysis was carried out to assess the effect of post-harvest storage on volatiles composition of green-ripe sea-freighted pineapple in comparison to air-freighted fruits harvested at full maturity. The latter fruits were characterised by volatiles described as potent odorants in pineapples, such as δ-octalactone, γ-lactones, 1-(E,Z)-3,5-undecatriene and 1,3,5,8-undecatetraene, as well as various methyl esters. In contrast, post-harvest storage of green-ripe sea-freighted fruits resulted in an increased formation of ethyl esters, acetates, acetoxy esters and alcohols, thus allowing the authentication of sea- and air-freighted pineapples, respectively. Particularly, compounds presumably derived from methyl-branched amino acid catabolism were identified in the fruits at later post-harvest stages. In addition, physicochemical traits were determined to characterise the fruit maturity stages.

Studies into the phenolic patterns of different tissues of pineapple (Ananas comosus [L.] Merr.) infructescence by HPLC-DAD-ESI-MS n and GC-MS analysis

In a comprehensive study, more than 60 phenolic compounds were detected in methanolic extracts from different tissues of pineapple infructescence by high-performance liquid chromatography with diode array detection and electrospray ionisation multiple-stage mass spectrometry (HPLC-DAD-ESI-MSn) as well as by gas chromatography-mass spectrometry (GC-MS). The analytical workflow combining both methods revealed numerous compounds assigned for the first time as pineapple constituents by their mass fragmentations. Pineapple crown tissue was characterised by depsides of p-coumaric and ferulic acid. In contrast, major phenolic compounds in pineapple pulp extracts were assigned to diverse S-p-coumaryl, S-coniferyl and S-sinapyl derivatives of glutathione, N-l-γ-glutamyl-l-cysteine and l-cysteine, which were also identified in the peel. The latter was additionally characterised by elevated concentrations of p-coumaric, ferulic and caffeic acid depsides and glycerides, respectively. Two peel-specific cyanidin hexosides were found. Elevated concentrations of isomeric N,N′-diferuloylspermidines may be a useful tool for the detection of fraudulent peel usage for pineapple juice production. Mass fragmentation pathways of characteristic pineapple constituents are proposed, and their putative biological functions are discussed.

Ripening-dependent metabolic changes in the volatiles of pineapple (Ananas comosus (L.) Merr.) fruit: I. Characterization of pineapple aroma compounds by comprehensive two-dimensional gas chromatography-mass spectrometry.

Qualitative ripening-dependent changes of pineapple volatiles were studied via headspace solid-phase microextraction and analyzed by comprehensive two-dimensional gas chromatography quadrupole mass spectrometry (HS-SPME-GC×GC-qMS). Early green-ripe stage, post-harvest ripened, and green-ripe fruits at the end of their commercial shelf-life were compared to air-freighted pineapples harvested at full maturity. In total, more than 290 volatiles could be identified by mass spectrometry and their linear retention indices. The majority of compounds comprise esters (methyl and ethyl esters of saturated and unsaturated fatty acids, acetates), terpenes, alcohols, aldehydes, 2-ketones, free fatty acids, and miscellaneous γ- and δ-lactones. The structured separation space obtained by GC×GC allowed revealing various homologous series of compound classes as well as clustering of sesquiterpenes. Post-harvest ripening increased the diversity of the volatile profile compared to both early green-ripe maturity stages and on-plant ripened fruits.

Authentication of pineapple (Ananas comosus [L.] Merr.) fruit maturity stages by quantitative analysis of γ- and δ-lactones using headspace solid-phase microextraction and chirospecific gas chromatography–selected ion monitoring mass spectrometry (HS-SPME–GC–SIM-MS)

Headspace solid phase microextraction and chirospecific gas chromatography-mass spectrometry in selected ion monitoring mode (HS-SPME-GC-SIM-MS) allowed quantitative determination of δ-lactones (δ-C8, δ-C10) and γ-lactones (γ-C6, γ-C8, γ-C10). A stable isotope dilution assay (SIDA) with d7-γ-decalactone as internal standard was used for quantitative analysis of pineapple lactones that was performed at three progressing post-harvest stages of fully ripe air-freighted and green-ripe sea-freighted fruits, covering the relevant shelf-life of the fruits. Fresh pineapples harvested at full maturity were characterised by γ-C6 of high enantiomeric purity remaining stable during the whole post-harvest period. In contrast, the enantiomeric purity of γ-C6 significantly decreased during post-harvest storage of sea-freighted pineapples. The biogenetical background and the potential of chirospecific analysis of lactones for authentication and quality evaluation of fresh pineapple fruits are discussed.

Quillajasides A and B: New Phenylpropanoid Sucrose Esters from the Inner Bark of Quillaja saponaria Molina.

The phenolic composition of freshly prepared aqueous extracts of the inner bark of Quillaja saponaria Molina was compared to that of commercially available Quillaja extracts, which are currently used as emulsifiers in foods and cosmetics. Major phenolics in both extracts were (+)-piscidic acid and several p-coumaroyl sucrose esters. Among the latter, two new compounds were isolated and characterized: α-l-rhap-(1→4)-α-l-rhap-(1→3)-(4-O-(E)-p-coumaroyl)-α-d-glup-(1→2)-(3-O-(E)-p-coumaroyl)-β-d-fruf (quillajaside A) and β-d-apif-(1→4)-α-l-rhap-(1→4)-α-l-rhap-(1→3)-(4-O-(E)-p-coumaroyl)-α-d-glup-(1→2)-(3-O-(E)-p-coumaroyl)-β-d-fruf (quillajaside B). In addition, a putative biosynthetic pathway of at least 20 structurally related p-coumaroyl sucrose esters was tentatively identified. Besides their antioxidant activity and their potential function as substrate for enzymatic browning reactions, the new compounds are highly characteristic for both the inner bark of Q. saponaria and commercial extracts derived therefrom. Consequently, they might serve as authenticity markers for the detection of Quillaja extracts in food and cosmetic formulations.

Assignment of distinctive volatiles, descriptive sensory analysis and consumer preference of differently ripened and post-harvest handled pineapple (Ananas comosus [L.] Merr.) fruits

Volatiles of differently ripened fresh pineapples were investigated by a non-targeted profiling analysis comparing fruits harvested at full maturity exported by rapid air freight to pineapples harvested at an earlier green-ripe stage. The latter fruits were exported by sea freight and analysed upon arrival at their destination and after post-harvest flavour genesis. Volatiles were analysed by headspace solid-phase microextraction, gas chromatography–mass spectrometry and multivariate statistical data analysis. Clear-cut differences in the volatile profiles were found. Fully ripe air-freighted pineapples were characterised by elevated concentrations of two 1,3,5,8-undecatetraene isomers, methyl 3-methylbutanoate and 4-methoxy-2,5-dimethyl-3(2H)-furanone, which have been reported as potent contributors to the pineapple flavour. Compared to fully ripened fruits, development of volatiles of sea-freighted pineapples upon arrival in Europe was rudimentary. Post-harvest storage of sea-freighted pineapples resulted in a different volatile profile due to the genesis of hydroxylated and acetoxylated methyl esters and hexanal. Subsequent descriptive sensory analysis was performed by trained panellists comparing retronasal odour and taste profiles. Fully ripe fruits were characterised by a pineapple-like note, fruity flavours and a sweet taste. In contrast, most of these attributes were rated at lower intensities when premature green-ripe fruits were tested. At the end of the post-harvest period, sea-freighted pineapples were characterised by fruity notes accompanied by a musty/corky- and cardboard-like off-flavour. Odour, taste and overall preference were significantly higher rated for air-freighted pineapples as revealed by an untrained consumer panel.

Carotenoids and xanthophyll esters of yellow and red nance fruits (Byrsonima crassifolia (L.) Kunth) from Costa Rica

Carotenoid profiles, by means of HPLC-PDA-MSn, and CIE-L*C*h° colour values of yellow and red nance fruits from Costa Rica were elucidated. Among 16 carotenoids detected, (all-E)-lutein was the most abundant accounting for >80% of the total carotenoids, followed by (all-E)-zeaxanthin (9-11%) and (all-E)-β-carotene (2-9%). Minor constituents were (Z)-isomers of lutein and β-carotene, as well as diverse lutein diesters. Among the esters, lutein dimyristate was the most abundant as substantiated by the comparison with a marigold flower extract. Total carotenoids in the peel (616.2 μg/100 g of FW in yellow nance and 174.2 μg/100 g of FW in red nance) were higher than in the pulp (39.4 μg/100 g of FW in yellow nance and 31.4 μg/100 g of FW in red nance). Since carotenoid profiles of yellow and red varieties were qualitatively similar, although the colour values showed significant differences (77.2 and 88.6 h° in peel and pulp of yellow nance, versus 32.7 and 67.3 h° in peel and pulp of red nance, respectively), pigments other than carotenoids may impart the colour of red nance. High lutein content renders nance fruit as a nutritionally relevant source of this micronutrient.