Ioannis Zabetakis

Strawberry Flavour: Analysis and Biosynthesis

Strawberry flavour, one of the most complicated fruit flavours, has been extensively studied. The different techniques applied to strawberry flavour analysis are critically reviewed. Amongst these numerous flavour components there are some with significant commercial value, so strawberries or strawberry cells have been used in order to study the biosynthesis of these compounds. Attention is given to those biosynthetic studies as a basis for an alternative way to produce natural strawberry flavour.

High pressure processing in jam manufacture : effects on textural and colour properties

Abstract High hydrostatic pressure-treated strawberry jam samples were examined with respect to their textural and colour properties, the aim being to establish the relationship between pectin concentration, texture and colour. Samples were prepared with varying amounts of pectin (0.1, 0.5, 2.5, 5, 7.5 and 10% w/w) and were processed using the same parameters (400 MPa, for 5 min at 25°C). After preparation, the samples were rheologically tested using a cone and plate configuration on a Creep Viscometry Oscillation rheometer. A colour spectrophotometer was used to monitor (at 505 nm) the changes in colour during storage. Comparing these experimental samples with commercially available samples of high pressure and traditional strawberry jams, it was found that the best texture was achieved when the pectin concentration was between 2.5 and 5% w/w. With increasing pectin concentration, the storage and loss moduli (indicators of liquid- and solid-like characteristics) were increased. Colour was found to be affected by the increasing pectin concentration, as the absorbance intensity was decreased, suggesting a relation between pectin and anthocyanin degradation.

The effect of high hydrostatic pressure on strawberry flavour compounds

Abstract The effects of high hydrostatic pressure on strawberry flavour compounds and the enzyme β-glucosidase were investigated. Strawberry ( Fragaria × ananassa , cv. Elsanta) samples were submitted to high pressure ranging from 200 to 800 MPa. After the high pressure treatment, the samples were kept for 24 h at three different storage temperatures (4, 20 and 30°C) and, thereafter, the flavour was extracted by simultaneous steam distillation-solvent extraction using dichloromethane. Analysis was carried out by GC–MS and HPLC. The analytes of this study are three acids (namely butanoic acid, 2-methyl-butanoic acid and hexanoic acid), one ketone (2,4,6-heptatrione) and three furanones (5-hexyl-dihydro- 3H -furan-2-one, 2,5-dimethyl-4-hydroxy- 2H -furan-3-one and 2,5-dimethyl-4-hydroxy- 2H -furan-3-one-glucoside). The highest flavour stability was observed when samples were treated with lower pressures and they were stored at 4 and 30° C. The enzyme β-glucosidase was found to be activated when pressures of 200 and 400 MPa were applied but inactivated considerably in the 600 and 800 MPa treatments.

2,5-Dimethyl-4-hydroxy-2H-furan-3-one and its derivatives: analysis, synthesis and biosynthesis—a review

Dimethyl-4-hydroxy-2H-furan-3-one is believed to be a key flavour constituent in many fruits and baked foods. The analy- tical and organic methods applied to the analysis of DMHF and its derivatives, synthesis and biosynthesis are reviewed. Possibilities for further elucidation of biosynthetic pathways and the biotechnological production of DMHF are considered. # 1999 Elsevier Science Ltd. All rights reserved. 1. The analysis of 2,5-dimethyl-4-hydroxy-2H-furan-3- one and its derivatives 2,5-Dimethyl-4-hydroxy-2H-furan-3-one (DMHF) is widely distributed in nature and has a very low flavour threshold value in water (410 ˇ5 mg/kg); hence, its eAect on food aroma is considerable (Latrasse, 1991). 2,5-Dimethyl-4-hydroxy-2H-furan-3-one occurs in nature in four forms (Fig. 1): 2,5-dimethyl-4-hydroxy-2H-furan- 3-one glucoside (DMHF glucoside), 2,5-dimethyl-4- hydroxy-2H-furan-3-one 6 0 -O-malonyl-b-D-glucopyrano- side (DMHF malonyl-glucoside), 2,5-dimethyl-4-meth- oxy-2H-furan-3-one (mesifuran) as well as the free aglycone (Latrasse, 1991; Mayerl, Naf, & Thomas, 1989; Roscher, Herderich, SteAen, Schreier, & Schwab, 1996a).

Enhancement of flavour biosynthesis from strawberry (Fragaria x ananassa) callus cultures by Methylobacterium species

Two important character-impact compounds of strawberry flavour, the furanones 2,5-dimethyl-4-hydroxy-2H-furan-3-one (DMHF) and 2,5-dimethyl-4-methoxy-2H-furan-3-one (mesifuran) were synthesized by strawberry tissue cultures derived from a cultivated species (Fragaria × ananassa, cv. Elsanta) after these were treated with Methylobacterium extorquens. These flavour compounds were analysed by HPLC-UV and their levels were compared in the treated and control tissues. In Methylobacterium extorquens treated callus cultures DMHF and mesifuran levels were 5.9 and 11.4 µg/g of fresh weight of callus respectively, compared to zero in the untreated ones. When Methylobacterium extorquens was fed with 1,2-propanediol, 2-hydroxy-propanal (lactaldehyde) was formed. This bacterial oxidation of 1,2-propanediol to lactaldehyde linked with the presence of 1,2-propanediol in strawberry suggests that the increased levels of the two furanones in the treated strawberry cultures is the result of Methylobacterium extorquens oxidative activity on 1,2-propanediol and the bioconversion by the plant cells of this oxidation product, lactaldehyde to DMHF and mesifuran.

Effects of olive pomace and olive pomace oil on growth performance, fatty acid composition and cardio protective properties of gilthead sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax)

Gilthead sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) were fed with two experimental diets: olive pomace diet and olive pomace oil diet, in order to examine whether fish oil substitution in fish feeds by olive oil production wastes, such as olive pomace and olive pomace oil, has an influence on growth performance, fatty acid composition and cardio protective properties of fish. Gilthead sea bream fed with both experimental diets exhibited satisfactory growth performance factors while sea bass did not. The total lipids of gilthead sea bream fed with olive pomace diet contained statistically decreased levels of fatty acids, while exhibited the most potent biological activity against platelet aggregation induced by Platelet Activating Factor. These data indicate that olive pomace can be used as a partial substitute of fish oil in fish feed improving its cardio protective properties.

The role of ?-glucosidase in the biosynthesis of 2,5-dimethyl-4-hydroxy-3(2H)-furanone in strawberry (Fragaria ananassa cv. Elsanta)

Some flavour and colour compounds are present in cells as glucosides. Their hydrolysis to form volatile aglycones is catalysed by glucosidases. Strawberry β-glucosidase (β-glucoside glucohydrolase, EC 3.2.1.21) was characterized in crude extracts of strawberry fruits. Enzymatic activity was measured by visible spectrophotometry using p-nitrophenyl-β-D-glucopyranoside as substrate. Strawberry β-glucosidase had pH optimum at pH 4 and temperature optimum at 60 °C. The enzyme followed typical Michaelis kinetics with a Km of 18.5 mM. The Vmax value was 474 × 10 −6 (IU/ml) for p-nitrophenyl-β-D-glucoside (40 °C). β-Glucosidase activity was high in unripe green strawberries, increased slightly during ripening and then decreased below pre-ripening levels in the fully ripe fruit. The levels of 2,5-dimethyl-4-hydroxy-2H-furan-3-one (DMHF) and DMHF-glucoside both increased greatly during ripening. The results are discussed in terms of the role of strawberry glucosidase on flavour biogenesis. Copyright

The uptake of nickel and chromium from irrigation water by potatoes, carrots and onions

Heavy metals, in general, can migrate from polluted soil and/or irrigation water to tuber plants, leading, after chronic consumption, to health problems. The scope of this study was to investigate the uptake of chromium and nickel by carrots (Daucus carrota), onions (Allium cepa) and potatoes (Solanum tuberosum) in a greenhouse experiment simulating the open-field irrigation conditions in the two biggest tuber producing regions of Greece (Asopos river in Viotia and Messapia in Evia). The study included cultivation of tubers for a period of approximately 4 months in six irrigation lines, each one provided by a water solution containing different levels of Cr(VI) and Ni(II) ranging from 0μg/l (control) to 250μg/l. The soil used was obtained from a certified organic greenhouse. Uptake of Cr was observed in onion leaves between 0 and 10μg/l water concentrations (+109.2 percent, p=0.006), 0μg/l and 20μg/l (+47.5 percent, p=0.006), 0μg/l and 50μg/l (+202.8 percent, p=0.006), 0μg/l and 100μg/l (+89.9 percent, p=0.028), 0μg/l and 250μg/l (+61.3 percent, p=0.009). Uptake of Ni was observed: (a) in onion leaves between 0 and 250μg/l water concentrations (+90.2 percent, p=0.076), (b) in onion shoots between 0 and 10μg/l (+39.1 percent, p=0.045), 0 and 250μg/l (+55 percent, p=0.047) and (c) in potatoes between 0 and 20μg/l (+28.1 percent, p=0.083). Our results suggest that irrigation water containing Cr and Ni can cross-contaminate onions and potatoes cultivated in a soil never previously polluted, anthropogenically, with heavy metals. No such results were found for carrots.

Structural elucidation of olive pomace fed sea bass (Dicentrarchus labrax) polar lipids with cardioprotective activities

The purpose of this study was to structurally characterise the polar lipids of sea bass (Dicentrarchus labrax), fed with an experimental diet containing olive pomace (OP), that exhibit cardioprotective activities. OP has been added to conventional fish oil (FO) feed at 4% and this was the OP diet, having been supplemented as finishing diet to fish. Sea bass was aquacultured using either FO or OP diet. At the end of the dietary experiment, lipids in both samples of fish muscle were quantified and HPLC fractionated. The in vitro cardioprotective properties of the polar lipid fractions, using washed rabbits platelets, have been assessed and the two most biologically active fractions were further analysed by mass spectrometry. The gas-chromatrograpy-mass spectrometric data shows that these two fractions contain low levels of myristic (14:0), oleic (18:1 cis ω-9) and linoleic acids (18:2 ω-6), but high levels of palmitic (16:0) and stearic acids (18:0) as well as eicosadienoic acid (20:2 ω-6). The first fraction (MS1) also contained significant levels of arachidonic acid (20:4 ω-6) and the omega-3 fatty acids: eicosapentaenoic acid (22:5) and docosahexaenoic acid (22:6). Electrospray-mass spectrometry elucidated that the lipid composition of the two fractions contained various diacyl-glycerophospholipids species, where the majority of them have either 18:0 or 18:1 fatty acids in the sn-1 position and either 22:6 or 20:2 fatty acids in the sn-2 position for MS1 and MS2, respectively. Our research focuses on the structure/function relationship of fish muscle polar lipids and cardiovascular diseases and structural data are given for polar lipid HPLC fractions with strong cardioprotective properties.

Concentration Levels of Trace Elements in Carrots, Onions, and Potatoes Cultivated in Asopos Region, Central Greece

The objective of the work was to investigate the correlation between the environmental pollution of Asopos river area in Viotia, Greece and the concentration of Ni, Cr, Cd, Pb, Cu, and As in specific crops (carrots, onions, and potatoes) produced in this region. Samples of these crops from Asopos and other Greek areas (control) were collected. For method accuracy, the Certified Reference Material, CRM 281 (trace elements in rye grass) was measured. Simultaneous multi-element graphite furnace atomic absorption spectrometry was used after a microwave acid digestion. The levels of Ni in Asopos food were found up to 9 times higher than control (e.g., Asopos potatoes had an average Ni content of 800 µg/kg compared to 78 µg/kg in control, whereas Asopos carrots had an average Ni content of 474 µg/kg compared to 93 µg/kg in control). Likewise, the levels of Cr were found to be about 2 times higher than control (e.g., Asopos carrots were found to have an average Cr content of 43 µg/kg compared to 20 µg/kg in control). The levels of Cd and Pb had a high variance in the Asopos sourced food. Arsenic was not detected in any sample. Our results indicate that the mean intake of trace elements (Ni, Cr, Pb, Cd, and Cu) by adults through consumption of crops from Asopos, for an average consumption pattern, generally is well below the Allowable Daily Intakes (ADIs). Comparison was also made with data from literature from Greece.