RESUMEN

Enzymatic time-temperature indicators (TTIs) usually suffer from instability and inefficiency in practical use as food quality indicator during storage. The aim of this study was to address the aforementioned problem by immobilizing laccase on electrospun chitosan fibers to increase the stability and minimize the usage of laccase. The addition of NaN3, as and enzyme inhibitor, was intended to extend this laccase TTI coloration rate and activation energy (Ea) range, so as to expand the application range of TTIs for evaluating changes in the quality of foods during storage. A two-component time-temperature indicator was prepared by immobilizing laccase on electrospun chitosan fibers as a TTI film, and by using guaiacol solution as a coloration substrate. The color difference of the innovative laccase TTI was discovered to be <3, and visually indistinguishable when OD500 reached 3.2; the response reaction time was regarded as the TTI's coloration endpoint. Enzyme immobilization and the addition of NaN3 increased coloration Km and reduced coloration Vmax. The coloration Vmax decreased to 64% when 0.1 mM NaN3 was added to the TTI, which exhibited noncompetitive inhibition and a slower coloration rate. Coloration hysteresis appeared in the TTI with NaN3, particularly at low temperatures. For TTI coloration, the Ea increased to 29.92-66.39 kJ/mol when 15-25 µg/cm2 of laccase was immobilized, and the endpoint increased to 11.0-199.5 h when 0-0.10 mM NaN3 was added. These modifications expanded the applicability of laccase TTIs in intelligent food packaging.

RESUMEN

Laccase was immobilized on a chitosan/polyvinyl alcohol/tetraethylorthosilicate electrospun film (ceCPTL) and colored with guaiacol to obtain a laccase time-temperature indicator (TTI) prototype. The activation energy (Ea) of coloration of the prototype was 50.89-33.62 kJ/mol when 8-25 µg/cm2 laccase was immobilized on ceCPTL, and that of lactic acid bacteria (LAB) growth in milk was 73.32 kJ/mol. The Ea of coloration of the TTI prototype onto which 8-10 µg/cm2 laccase was immobilized was in the required range for predicting LAB growth in milk. The coloration endpoint of the TTI prototype onto which 10 µg/cm2 (0.01 U) laccase was immobilized could respond to the LAB count reaching 106 colony-forming units (CFU)/mL in milk during a static temperature response test, and the prediction error was discovered to be low. In dynamic temperature response experiments with intermittent temperature changes between 4 and 25 °C, the coloration rate of the laccase TTI prototype was consistent with LAB growth. The results of this study indicate that the laccase TTI prototype can be applied as a visual monitoring indicator to assist in evaluating milk quality in cold chains.

RESUMEN

Kumquat and calamondin are two small-size citrus fruits. Owing to their health benefits, they are traditionally used as folk medicine in Asian countries. However, the research on flavonoids and biological activities of kumquat and calamondin have received less attention. This review summarizes the reported quantitative and qualitative data of phenolic compositions in these two fruits. Effects of maturity, harvest time, various solvent extractions and heat treatment of phenolic compositions, and bioactivities were discussed; distributions of the forms of phenolic compounds existing in kumquat and calamondin were also summarized. Furthermore, biological activities, including antioxidant, antityrosinase, antimicrobial, antitumor, and antimetabolic disorder effects, have also been discussed. Effective phenolic components were proposed for a certain bioactivity. It was found that C-glycoside flavonoids are dominant phenolic compounds in kumquat and calamondin, unlike in other citrus fruits. Up to now, biological activities and chemical characteristics of C-glycoside flavonoids in kumquat and calamondin are largely unknown.

Asunto(s)

RESUMEN

The total phenolic and flavonoid content of extracts from peel of kumquat were higher than those from pulp, and those extracted from immature kumquat were higher than those from mature kumquat. The highest levels of phenolic and flavonoid content were obtained in hot water extracts. The flavonoids of kumquat extracted from hot water were mainly soluble conjugated compounds, including C-glycosides, such as 3',5'-di-C-ß-glucopyranosylphloretin (DGPP), acacetin 8-C-neohesperidoside (margaritene), acacetin 6-C-neohesperidoside (isomargaritene), apigenin 8-C-neohesperidoside, and O-glycosides, such as acacetin 7-O-neohesperidoside (fortunellin), isosakuranetin 7-O-neohesperidoside (poncirin) and apigenin 7-O-neohesperidoside (rhoifolin). A positive relationship existed between total phenolic content and DPPH scavenging potency (p<0.001). Total flavonoid content showed a similar correlation (p<0.001) to DPPH scavenging potency. The effective flavonoids contributing to antioxidant activity were DGPP and apigenin 8-C-neohesperidoside, which could be extracted in high amounts, by hot water at 90°C, from immature kumquat peel.

Asunto(s)

RESUMEN

A seven flavonoids in hot water extract of immature kumquat (Citrus japonica var. margarita) were identified and quantified (mg/100g fresh fruit): 3',5'-di-C-ß-glucopyranosylphloretin (DGPP, 285.9 ± 2.9 mg/100g), acacetin 8-C-neohesperidoside (margaritene, 136.2 ± 2.6 mg/100g), acacetin 6-C-neohesperidoside (isomargaritene, 119.1 ± 1.8 mg/100g), fortunellin (acacetin 7-O-neohesperidoside, 28.5 ± 0.7 mg/100g), apigenin 8-C-neohesperidoside (16.9 ± 0.1mg/100g), poncirin (isosakuranetin 7-O-neohesperidoside, 5.1 ± 0.1mg/100g), and rhoifolin (apigenin 7-O-neohesperidoside, 2.0 ± 0.1mg/100g). When immature kumquat was dried at 110 and 130°C for 0.5h, the antioxidant activity, total phenolic content and identified flavonoids increased. The UV absorbance of browning products of immature kumquat dried at 130°C for 1.5h increased dramatically, while the identified flavonoids decreased. Therefore, it was concluded that drying below 130°C for 1.0 h, could release phenolic compounds, which resulted in the increasing antioxidant activity. Drying at 130°C for 1.5h, it might be due to the effect of formed browning products.

Asunto(s)

RESUMEN

Citrus essential oils are widely applied in food industry as the backbone of citrus flavors. Unfortunately, due to relatively simple chemical composition and tremendous price differences among citrus species, adulteration has been plaguing the industry since its inception. Skilled blenders are capable of making blends that are almost indistinguishable from authentic oils through conventional gas chromatography analysis. A reversed-phase high performance liquid chromatography (HPLC) method was developed for compositional study of nonvolatile constituents in essential oils from major citrus species. The nonvolatile oxygenated heterocyclic components identified in citrus oils were proved to be more effective as markers in adulteration detection than the volatile components. Authors are hoping such an analysis procedure can be served as a routine quality control test for authenticity evaluation in citrus essential oils.

RESUMEN

Hot water extract of immature calamondin peel contains high total phenolic content, which shows significant correlation to DPPH scavenging potency. By heat treatment, the extraction yields of naringin, tangeretin, ferulic acid, p-coumaric acid and gallic acid increased, but the amount of 3',5'-di-C-ß-glucopyranosylphloretin (DGPP) decreased drastically. The major soluble phenolic compounds in the nonpolar extract are nobiletin and tangeretin, while DGPP and hesperidin are in the hot water extract. For insoluble phenolic compounds, ferulic acid, p-coumaric acid and sinapic acid are mainly in ester linkage form. After heat treatment, gallic acid and p-coumaric acid are the major increased soluble and insoluble phenolic acids, respectively. This indicates that high temperature heating (150°C) probably produces two major effects: (1) degradation of flavonoids, such as DGPP and hesperidin; (2) destruction of the cell wall structure, leading to an increase in soluble nobiletin, tangeretin and gallic acid, as well as insoluble ferulic and p-coumaric acids.

Asunto(s)

RESUMEN

Calamondin has been demonstrated to exhibit antioxidant function and tyrosinase inhibitory activity, which might be attributed to its flavonoid compounds. To improve their application, the flavonoid compositions and antioxidant activity of calamondin extracts, prepared by different solvents, were investigated. The results showed that total phenolic and flavonoid contents of extracts from peel of calamondin were higher than that from pulp, except the flavonoid content in hot water extract. The flavonoids found in extracts of calamondin were 3',5'-di-C-ß-glucopyranosylphloretin (DGPP), naringin, hesperidin, nobiletin, tangeretin, and diosmin. DGPP exhibited the highest quantity, while naringin and hesperidin were the other two major flavonoids. The content of DGPP in hot water extract of peel was higher than in extracts of organic solvents, however, the contents of nobiletin and tangeretin were found only in extracts of organic solvents. The highest levels of total flavonoids and DGPP were obtained in hot water extract from peel at 90°C. The extracts of hot water and ethyl acetate showed higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging potency than that of ethanol and methanol. A positive relationship existed between total phenolic contents and DPPH scavenging potency (p < 0.01), while total flavonoid compositions also showed correlation (p < 0.05). Thus, DGPP, naringin, and hesperidin might contribute to antioxidant activity. Collectively, the hot water extract of calamondin peel might have potential for health food and cosmetic applications due to its good antioxidant activity and high level of DGPP.

RESUMEN

The antioxidant activity and the flavonoids of mature and immature calamondin (Citrus mitis Blanco) peel were investigated. The hot water extract of immature calamondin peel exhibited the highest oxygen radical absorbance capacity (ORAC), reducing power, and superoxide scavenging effect. 3',5'-Di-C-ß-glucopyranosylphloretin, naringin, hesperidin, nobiletin, and tangeretin are the five major flavonoids found in hot water extract with the levels of 6888±522, 2333±157, 1350±94, 165±13, and 8±4 mg/100 g dry basis, respectively. The contents of nobiletin and tangeretin increased after ripening. The hot water extract of immature calamondin peel was fractionated using a semi-preparative HPLC. Fraction VI showed the highest ORAC value (28.02±2.73 mmol Trolox equivalents (TE)/g fraction) and two compounds, naringin and hesperidin, were identified as the major active components attributed to the antioxidant activity. Fraction V contained 3',5'-di-C-ß-glucopyranosylphloretin, which revealed low ORAC value with 7.43 mmol TE/g fraction. However, it might also contribute to antioxidant activity in immature calamondin peel due to its greatest quantity.

Asunto(s)

RESUMEN

There is broad range of applications in the use of tyrosinase inhibitors for suppressing unwanted hyperpigmentation in human skin and enzymic browning in fruits. In searching effective tyrosinase inhibitors from natural products, the components in unripe calamondin (Citrus mitis Blanco) peel were investigated by performing bioassay-directed fractionation and chromatographic separation coupled with tyrosinase inhibition assay. Herein it is reported for the first time that (1) there is a rich content of 3',5'-di-C-ß-glucopyranosylphloretin in unripe calamondin peel, 3.69±0.44g/100g dry basis, (2) this C-glycosylated flavonoid showed the strongest inhibitory activity against tyrosinase among the components in this fruit, with an IC(50) of 0.87mg/ml, and (3) that unripe calamondin peel is also a rich source of naringin and hesperidin, 1.25% and 0.73% by dry weight, respectively, which also expressed strong tyrosinase inhibitory property.

Asunto(s)