1,721,002 research outputs found
Effect of beta-cyclodextrin addition on quality of precooked vacuum packed potatoes
No full textThe usefulness of b-cyclodextrin (b-CD) in enhancing the food and nutritional quality of precooked potatoes was studied. After blanching, potato slices were cooled. This was followed by dipping in solutions containing b-CD, ascorbic and citric acids, either alone or in combination
with b-CD, and vacuum packaging in pouches. The potatoes were pasteurised/precooked and cooled.
These samples were then analyzed for colour parameters, microbial count, Resistant Starch (RS) concentration, fat content after a frying test immediately and after 7, 14 and 28 days of storage at 4 °C.
Results showed that dipping with b-CD gave the lightest colour (DL*) and a more attractive appearance.nHowever, growth of aerobic mesophilic bacteria was observed in samples dipping in solutions with b-CD
alone. From the nutritional point of view, the effect of b-CD on the RS content of potatoes may be related to storage time
3,4-Dihydroxyphenylalanine gel diffusion assay for polyphenol oxidase quantification
No full textWe have developed a simple, inexpensive plate assay to detect and quantify polyphenol oxidase (PPO)
activity from different origins. The logarithm of enzyme activity is linearly correlated with the diameter
of the dark, L-3,4-dihydroxyphenylalanine (L-DOPA) oxidized circles produced in the gel, thereby allowing quantification of PPO. Moreover, precision and high reproducibility of the assay were confirmed by statistical
analysi
Dog Rose and pomegranate extracts as agents to control enzymatic browning
No full textTo demonstrate that two natural products obtained with minimal processing can be used as antibrowning
agents, extracts of dog rose hips and pomegranate arils were assayed for inhibition of tyrosinase and
polyphenol oxidase activity. The efficiency of antibrowning activity was evaluated in terms of absorbance and
polyacrylamide gel zymograms. In addition to the in vitro studies, melanosis in foods such as artichokes,
mushrooms and pear juice was evaluated. The results revealed that dog rose hip extract was more effective
than pomegranate aril extract. Moreover, high performance liquid chromatography analysis showed that
extracts from both sources had many potential inhibitors of polyphenol oxidase and tyrosinase activity
Detection of pectinmethylesterase activity in presence of methanol during grape pomace storage
No full textMethanol is an unwanted component in the production of spirit beverages. Its presence in grape pomace stored until distillation
greatly affects the composition of the final product, which requires redistillation, modifying the aromatic characteristics of the distillate.Consequently, reduction of methanol, by controlling its formation during pomace storage, can increase the quality of grappa. The aim of this work was to monitor pectinmethylesterase activity during grape pomace storage, in order to identify its presence related to methanol release. The enzyme activity was detected during various storage times by spectrophotometric and electrophoretic methods. Results show
that yeasts do not contribute to PME production. Moreover, by using paranitrophenyl acetate, a specific substrate for esterase, also as PME substrate, we demonstrate the presence of several enzymes hydrolysing ester bond
Stabilità dell'attività antiossidante di estratti di erbe aromatiche in funzione di pH e temperatura
No full textAntioxidant properties of extracts from different aromatic herbs were studied. Looking to food application, the paper focused on the effect of pH and temperature on their storage stability
Determinazione quantitativa di elementi minerali presenti in uva mosto e vino Merlot
No full textImpiego della metodica ICP-OES per la determinazione di elementi minerali di interesse tecnologico e nutrizionale in campioni di mosto e vin
Deriphat 2-DE to visualize polyphenol oxidase in Moscato and Prosecco grape
No full textThe Deriphat 2-DE was used to visualize polyphenol oxidase (PPO) isoforms of Moscato and Prosecco grape extracts, partially purified and characterized. Catecholase has similar
values in the two varieties, whereas Moscato cresolase data are almost 54% higher. In the first dimension, the PPO of both varieties may be detected by SDS-PAGE, but native PAGE
(N-PAGE) gave negative results. For this reason, the samples were solubilized in the zwitteronic detergent Deriphat, which was also included in the gel and the cathodic buffer.
Deriphat migrated together with the cathodic buffer, maintaining protein solubility and revealing the PPO profiles of Moscato and Prosecco extracts in native conditions. The
combination of Deriphat-PAGE (D-PAGE) and SDS-PAGE (2-DE) also resulted in improved separation efficiency in resolving PPO and specialized stains in evaluating PPO activities. The control, represented by IEF for the first-dimensional separation, had a lower number of spots, demonstrating the higher capacity of Deriphat 2-DE to isolate PPO isoforms from grape extracts. The Deriphat 2-DE method described here is simple but powerful,
and the resulting information will be a useful tool for further proteomic research
Estrazione e parziale caratterizzazione di polifenolossidasi di uve Moscato e Prosecco.
No full textThe goal of this work was to characterize the polyphenoloxidase extracted from Moscato and Prosecco grapes. Enzymatic extracts partially purified showed the maximum activities respectively at pH 5.0 and 5.5 and were thermically stables between 25°C and 40°C. Some inhibitors were tested and sodium methabisulphite showed the best efficency in both varieties also with the lowest concentration. To obtain the same results with ascorbic and citric acids, high concentration should be used
A study on the relationship between the volatile composition of Moscato and Prosecco Grappa and enzymatic activities involved in its production
No full textThe enzymatic transformations during storage of pomaces
greatly affect the composition of Italian Grappa. This study
examines the impact of pectin methylesterase (PME), β-
glucosidase (βG) and esterases (ESTs) on the composition of
Moscato and Prosecco Grappa. Grape pomaces were fermented
for differing periods of time. After protein extraction, the
enzymatic activities were detected by spectrophotometric and
electrophoretic methods. To determine by gas chromatography
the evolution of methanol, terpenes, ethyl acetate and lactate in
pomaces and Grappa samples, distillations by Cazenave equipment
and a traditional copper alambic were performed. Sensorial
evaluation was carried out. There is a close relationship between
the PME activity of grape pomaces, the degree of pectin methylation, and the concentration of methanol before distillation. The results obtained suggest that inhibition of grape pomaces PME may be adopted to control methanol concentration. The glycosidases of grape and/or yeast seem to have a limited effect on the release of volatile compounds from glycosides located in grape skins. As regards the contribution of grape and microorganism esterase, several hypotheses are discussed
A preliminary study on changes in phenolic content during Bianchetta Trevigiana winemaking
No full textAutochthonous grapevine varieties are considered a biodiversity resource in viticulture and an opportunity for Italian sustainable wine production. In this study, the ancient white wine variety Bianchetta Trevigiana, considered part of the agricultural history of the Veneto region, was vinified alone,with or without maceration, in order to better understand its technological and organoleptic characteristics, with the overall objective of valorising and re-evaluating it. The evolution of phenols that are very important for the organoleptic and technological profile of wine was
monitored during the winemaking process. Results show that contact with grape skins and seeds enhance phenol extraction and produces must and wine with higher concentrations of these compounds. Moreover, it was found that the concentration of flavanols in Bianchetta Trevigiana is similar or even higher than that of red wines
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