1,721,045 research outputs found
Ruolo della β-glucosidasi isolata da attività enzimatiche collaterali sul rilascio di trans-resveratrolo nei vini (ROLE OF B-GLUCOSIDASE ISOLATED FROM COLLATERAL ENZYMATIC ACTIVITIES IN RELEASING TRANS-RESVERATROL IN WINES)
No full textMYROSINASE ACTIVITY AND QUALITY PARAMETERS ON FRESH-CUT CHINESE CABBAGE STORED AT TWO DIFFERENT TEMPERATURES.
No full textRUOLO DI Β-GLUCOSIDASI ISOLATA D’ATTIVITÀ ENZIMATICHE COLLATERALI SUL RILASCIO DI TRANS-RESVERATROLO NEI VINI.
No full textNATURAL INDICO FROM ISATIS TINCTORIA L. FOR THE VALORISATION OF SICILIAN CROPS
No full textIsatis tinctoria L. or woad (Brassicaceae) is an upright herbaceous biennal species up to 120 cm in
height. It is in Mediterranean counlries, a common plant cultivated through out centuries to produce
the blue dye indigo. With increasing concem for sustainability and a demand from consumers for
naturally sourced products, there is a revival of interest in naturai indigo as an agricultural crop
produci. Indigo is formed after the extraction of indigo precursors in the leaves of these plants:
mainly isatans in woad These compounds are extracted by steeping leaves in warm water. With
woad, the addition of alkali to the steep water releases free indoxyl, which forms indigo after a
vigorous aeration. Indigo is hydrophobic and insoluble in water, so that it sedimcnts readily, and the
solid indigo can be readily washed and dried. Indigo is synthesized from two precursor molecules of
indoxyl, deriving from plant secondary metabolism. Recently clarified the nature of indigo
precursors in woad (Isatis tinctoria L.), by identifying the major indoxyl glycoside as isatan A
(indoxyl-3-O-(60-O-malonyl-b-D-ribohexo-3-ulopyranoside)), and by correcting the structure of the
related isatan B (indoxyl-3-0-b-D-ribohexo-3-ulopyranoside). The seasonal variation of indoxyl
glyeosides in woad leaves was investigated and the influence of various post-harvest treatments was
studied and Isatans A and B disappeared completely when the leaf material was submitted to a
conventional drying process. In contrast, the indican coment in leaves increased significantly, and
the extent of this increase was temperature-dependent. These precursor can be identified and
quantified by HPLC method since their quantity in dependent on the species and the harvest period.
The modem extraction method of indigo from woad uses the water solubility of the indigo
precursors in steeping the leaves in hot water. The precursors are broken down to indoxyl and sugar
moieties by endogenous enzymes in plant (glycosidases), but in the extraction method this is done
by alkali with aeration. The purity of plant-derived indigo even with the modem extraction method
is somewhat low when compared to the synthelic indigo. Naturai indigo contains besides indigo,
impurities such as indirubin, indigo-brown, indigo gluten and minerai matter. Several authors
indicate that indigo can be extracted from woad with a purity of 90% if three conditions are met: the
leaves contain a sufficiently high yield of indigo precursors; the leaves are rinsed free of soil; and
the indigo is sedimented in an acid medium
Immobilized beta-glucosidase for wine-making industry: Study of biocatalyst operational stability in laboratory scale continuous reactor
No full textThe stability of β-glucosidase immobilized on chitosan pellets was studied under operational conditions in continuous stirred tank membrane reactors. The rate of enzyme deactivation was monitored at 25°C using p-nitrophenyl β-d-glucopyranoside as model substrate. The medium was also supplemented with chemicals present in the wines, namely fructose, ethanol, nerol, linanol and geraniol. Fructose did not decrease biocatalyst stability, while alcohol affected enzyme half-life from 2586 h at 3% (w/v) ethanol to 1378 h at 12% (w/v). The addition of terpenols to solution containing 10% (w/v) alcohol reduced the half-life by a further 10%. Enzyme stability was not dependent on substrate concentration and was considered satisfactory for an industrial process (half-life 1.2 years). These results were independent of the use of wet stored pellets or of samples freeze-dried (24 h at –60°C). No added chemical influenced enzyme specific activity up to the tested limits: fructose 20 mM, terpenols 5 ppm each, ethanol 12% (w/v)
STRATEGIES FOR THE EXTENSION OF THE SHELF LIFE OF READY TO EAT PRICKLY PEAR FRUITS
No full textThe prickly pear fruit (Opuntia ficus indica L. Miller) belongs to the Cactaceae family.
The fruit is a berry, composed by an epicarp and the pulp, which represents the
edible portion. At maturation, the epicarp turns yellow, red or white, depending on
the cultivar. In Italy, the prickly pear is mainly cultivated in Sicily (90% of the national
production). The fruit is very sensitive to low storage temperatures (< 5°C) which cause
chilling injuries. The fruits can be successfully commercialized as a ready-to-eat product,
peeled and suitably packaged. The main limit to its production is the formation
of off-flavours due to different factors, such as the growth of microorganism and the
action of endogenous enzymes (lipid oxidation). In fact, the oxidoreductases are directly
responsible for the lipid oxidation, which has influence on the production of off-flavours,
on the structure and on the shelf-life of the fruit. The lipoxygenase (LOX) is a dioxygenase
which catalyzes the oxidation of polyunsaturated fatty acids to hydroperoxides.
The aim of this work was to compare different packaging technologies to extend the
shelf life of ready-to-eat prickly pear fruits. The LOX activity, microbial counts and gas
composition were evaluated for non-treated samples packed in ordinary atmosphere
and in two modified atmospheres having different O2 and CO2 composition (MA1 5%
O2, 2% CO2, 93%N2; MA2 2% O2, 5% CO2, 93% N2) and for samples treated either with
a blanching or with a blanching followed by a dipping in a citric acid solution. The
pretreatment conditions are essential for the LOX activity, in particular the blanching
reduced its activity by at least 30% especially in combination with fruit acidification and
limited the microbial proliferation. As a result of suitable pretreatment and packaging
operations the shelf life of ready-to-eat prickly pears can be successfully extended
Effetti dell’essiccamento sull’attività polifenolossidasica e pattern antiossidante di pomodoro ciliegino(Effects of drying process on polyphenol oxidase activity and antioxidant pattern changes of Sicilian cherry tomato)
No full textCharacterization of pectinmethylesterase, β-galactosidase and ascorbate oxidase from Sicilian blood orange.
No full text
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