Color quality of Oregon strawberries--impact of genotype, composition, and processing.

This investigation was to evaluate fruit color and study the effect of processing on color quality of strawberry products. Three color instruments with different viewing angles, viewing areas, and sample presentation geometries were compared for their effectiveness in measuring CIEL*C*h(o) color values for fresh fruits of 6 strawberry genotypes. There were significant differences between genotypes as well as between instruments. Fruits from the Totem genotype were frozen, canned, and made into jam. Color changes were measured along with the following compositional determinations: total monomeric anthocyanins (ACN), total phenolic content (TPC), and percent polymeric color. ACN in fresh strawberries ranged from 37.1 mg to 122.3 mg per 100 g of fresh fruit. Freezing resulted in an apparent increase in ACN and transfer of 70.2% of the anthocyanins from the berries into juice. Physical transfer of pigments to syrup also occurred with canning: there was approximately 70% loss in ACN, about 20% increase in polymeric color, and 23.5% decrease in TPC. Pronounced color change and substantial losses in ACN and TPC of strawberry jams occurred during processing and 9 wk of storage. Storage of jams at 38 degrees C compared to 21 degrees C over a period of 9 wk resulted in marked losses of ACN and TPC.

Polyphenolic composition of raisins.

The polyphenolics of raisins were extracted, separated by HPLC, and characterized by their UV-vis spectra, and their concentrations measured. Color measurements and browning indices were also determined. Samples (n = 20) included sun-dried, dipped, and golden raisins. Comparisons were also made with fresh and frozen Thompson Seedless grapes. Golden raisins (which are treated with SO(2)) had the highest amount of hydroxycinnamic acids and the highest lightness values. In comparison with fresh grapes, percent losses of the two major hydroxycinnamics (caftaric and coutaric acids) in sun-dried, dipped, and golden raisins were on the order of 90%. Flavonols were not influenced by processing as much as hydroxycinnamics, while procyanidins and flavan-3-ols were completely degraded in all raisin samples. Formation of hydroxymethylfurfural and loss of amino acids in sun-dried and dipped raisins are ascribed to Maillard browning reactions.

Molar absorptivity and color characteristics of acylated and non-acylated pelargonidin-based anthocyanins.

The effects of glycosylation and acylation on the spectral characteristics, molar absorptivity, and color attributes of purified acylated and non-acylated pelargonidin derivatives were compared. Pigments were obtained from strawberries, radishes, red-fleshed potatoes, and partially hydrolyzed radish pigments. Individual pigments were isolated by using semipreparative HPLC. Spectral and color (CIELch) attributes of purified pigments were measured. Molar absorptivity ranged from 15 600 to 39 590 for pelargonidin-3-glucoside (pg-3-glu) and pg-3-rutinoside-5-glucoside acylated with p-coumaric acid, respectively. The presence of cinnamic acid acylation had a considerable impact on spectral and color characteristics, causing a bathochromic shift of lambda(max). Sugar substitution also played an important role, with a hypsochromic shift caused by the presence of glycosylation. Pg-3, 5-diglu and pg-3,5-triglu possessed a higher hue angle (>40 degrees ) than the other pg derivatives at pH 1.0, corresponding to the yellow-orange region of the color solid. Acylation with malonic acid did not affect lambda(max) and showed little effect on color characteristics. The solvent system had an effect not only on the molar absorptivity, but also on the visual color characteristic of the pigments.

Electrospray and tandem mass spectroscopy as tools for anthocyanin characterization.

The utility of electrospray and tandem mass spectroscopy (ES-MS and MS-MS) in anthocyanin characterization was tested using different anthocyanin extracts. Anthocyanins were semipurified by using a C-18 resin, washed with acidified water followed by ethyl acetate, and recovered with acidified methanol. Samples were directly injected into a mass spectrometer in either aqueous or methanolic solutions. The positive charge of anthocyanins favored fast and effective ES-MS detection of intact molecular ions. Little interference from other compounds was observed when the ethyl acetate cleaning procedure was used. Tandem mass spectroscopy provided clear and characteristic fragmentation patterns. The voltage used affected only the proportions at which these fragments were present. ES-MS may be used as a fast procedure for identification of anthocyanins, requiring minimal sample preparation. In combination with HPLC, ES-MS and MS-MS could be very powerful tools for anthocyanin characterization and monitoring the authenticity of anthocyanin-containing fruit juices and vegetable extracts.

Characterization of sinapyl derivatives in pineapple (Ananas comosus [L.] Merill) juice.

Three previously unidentified phenolic compounds were found in pineapple (Ananas comosus [L.] Merill) juice in substantial concentrations and were isolated by semipreparative reverse phase HPLC. The structures were elucidated from UV spectra, acid hydrolysis, and subsequent amino acid analysis, mass spectrometry, and two-dimensional NMR spectroscopy. The compounds are identified as S-sinapyl-L-cysteine, N-L-gamma-glutamyl-S-sinapyl-L-cysteine, and S-sinapylglutathione.

Stable isotopic carbon composition of apples and their subfractions--juice, seeds, sugars, and nonvolatile acids.

The 13C:12C ratios of 8 authentic apple juice samples and their subfractions were determined by mass spectrometry. Apples from Argentina, Mexico, New Zealand, and the United States were processed into juice; pulp was collected from the milled fruit and seeds were collected from the press-cake. Sugars, nonvolatile acids, and phenolics were isolated from the juice by treatment with ion-exchange resins and polyvinylpyrrolidone (PVPP). The mean value for all juice samples was -24.2% which is close to the values reported by other investigators. Juice from apples grown in Argentina, Mexico, and New Zealand did not differ from U.S. samples. The isotopic composition of the subfractions ranged from -22.0 to -31.0%. The values for the pulp were essentially the same as for juice. The sugar fraction was slightly less negative than the juice; the nonvolatile acid and phenolic fractions were more negative. The levels of nonvolatile acids and phenolics in apple juice are low, however, so these compounds contribute little to overall delta 13C values in juice.

Apple juice composition: sugar, nonvolatile acid, and phenolic profiles.

Apples from Michigan, Washington, Argentina, Mexico, and New Zealand were processed into juice; the 8 samples included Golden Delicious, Jonathan, Granny Smith, and McIntosh varieties. Liquid chromatography was used for quantitation of sugars (glucose, fructose, sucrose, and sorbitol), nonvolatile acids (malic, quinic, citric, shikimic, and fumaric), and phenolics (chlorogenic acid and hydroxymethylfurfural [HMF]). Other determinations included pH, 0Brix, and L-malic acid. A number of compositional indices for these authentic juices, e.g., chlorogenic acid content, total malic - L-malic difference, and the HMF:chlorogenic ratio, were at variance with recommended standards. The phenolic profile was shown to be particularly influenced by gelatin fining, with peak areas decreasing by as much as 50%. The L-malic:total malic ratio serves as a better index for presence of synthetic malic acid than does the difference between the 2 determinations. No apparent differences in chemical composition could be attributed to geographic origin.

Detection of adulteration in blackberry juice concentrates and wines.

Adulteration of blackberry juice concentrates and wines with juice of sorbitol-containing fruits was detected by determining carbohydrates by high performance liquid chromatography, gas-liquid chromatography, and thin layer chromatography. Sorbitol is not fermented by yeast and can be detected in wines made from blackberry juice concentrates that contain sorbitol. High levels of sorbitol and quinic and malic acids suggest that an imported blackberry concentrate may have been adulterated with plum. Degradation of anthocyanin pigments during processing and storage limits the utility of pigment analyses in detecting adulteration.

Free sugars and sorbitol in fruits--a complication from the literature.

The glucose, fructose, sucrose, and sorbitol content of apple, pear, plum, cherry, grape, strawberry, raspberry, blackberry, and peak fruit was compiled from the literature; their range, mean, standard deviation, and percent coefficient of variance were calculated. The individual fruits have characteristic patterns relating to their sorbitol content, glucose: fructose ratio, and sucrose content which are influenced to only a small degree by variety, season, or geographic origin. Processing in many cases has a marked effect on sucrose content.