Marina Carbonaro

Polyphenoloxidase activity and polyphenol levels in organically and conventionally grown peach (Prunus persica L., cv. Regina bianca) and pear (Pyrus communis L., cv. Williams)

Abstract Polyphenoloxidase (PPO) activity and total polyphenol content were tested in organically and conventionally grown whole fruits, peach ( Prunus persica L., cv. Regina bianca) and pear ( Pyrus communis L., cv. Williams), in order to evaluate the existence of a relationship between these parameters and of differences between fruits obtained with the two cultivation practices. Organic fruits were obtained on three different grounds: subterranean clover (sample A), spontaneous weed cover (sample B) and tilled (sample C). From the latter soil, the conventionally grown fruits were produced. All organic peach samples showed a highly significant ( P P

Absorption of Quercetin and Rutin in Rat Small Intestine

Background/Aims: Dietary antioxidant flavonoids, especially flavonols, are ubiquitous constituents of plant foods with potential health-promoting effects. However, the actual bioavailability of these compounds in vivo, especially in the prevalent glycosidic form, remains a controversial point in making an assessment of their biological importance. Thus, absorption of quercetin and rutin in the small intestine has been determined. Methods: The bioavailability of quercetin and rutin (quercetin-3-rutinoside) was assessed in vivo, with single-meal experiments with rats and by an in vitro method with ligated loops of rat small intestine. The amount of quercetin or rutin in the plasma of rats or in the lumen of each intestinal segment was assayed by maximum absorption in the UV/VIS optical spectrum as was the amount of compound that had crossed the gut wall into the incubation buffer. In addition, uptake of [14C]quercetin was tested in vitro. Results: Absorption of both quercetin and rutin from the small intestine of rat was evident. However, rutin appeared to be absorbed more slowly than quercetin. Experiments with [14C]quercetin showed that only 1.5% quercetin crossed the gut wall in vitro and more than half of the total quercetin was bound to the small intestinal tissue. Conclusions: Both quercetin and rutin can attach to and traverse the small intestine of the rat. Binding of flavonoids to the intestinal wall components may however greatly limit their absorption from the small intestine.

Influence of protein components (G1, G2 and albumin) on Fe and Zn dialysability from bean (Phaseolus vulgaris L.)

The influence of bean proteins on in vitro Fe and Zn dialysability was studied. Albumin and globulins (G1, G2) from Phaseolus vulgaris were characterised by SDS-PAGE and disc electrophoresis. Fe and Zn dialysability from whole flour was 2.28 and 27.5% respectively. Among protein fractions, albumin showed the lowest mineral dialysability (0.4% for Fe, 2.5% for Zn) in spite of having the highest Fe and Zn content. Globulins (G1 and G2) differed mainly in Fe dialysability (2.99 and 5% respectively), while presenting a similar Zn dialysability (20.3 and 23.6% respectively). Protein dialysability from bean protein fractions showed the same trend observed for minerals (albumin < G1 < G2). Unlike the whole seed, in protein fractions protein and Fe solubility showed the same behaviour, i.e. rising in the pepsin phase of digestion and decreasing in the pancreatic phase. These differences suggest that the intermediate products of protein digestion are responsible for Fe binding and solubilisation from bean protein ...

Influence of the method of protein extraction on the in-vitro evaluation of mineral dialysability from legumes

Abstract The aim of this study was to investigate to what extent the in-vitro evaluation of iron, zinc and protein dialysability from legumes is influenced by the method of globulins extraction (G1, G2). According to classical methods, globulins were first extracted into salt solutions containing ascorbic acid. Because of the enhancing effect of ascorbic acid on iron availability, globulins extraction was also carried out in the absence of ascorbic acid. In the presence of ascorbic acid, a parallel reduction in total protein content and in iron and zinc content was detected, suggesting an interaction between minerals and protein components. Ascorbic acid markedly improved protein dialysability and G2 always showed a higher dialysability than G1. In the absence of ascorbic acid, iron dialysability was 3.0% from G1 and 5.5% from G2, while ascorbic acid caused up to a three-fold increase in iron dialysability. Ascorbic acid did not influence zinc dialysability (20% for G1 and 24% for G2). For both globulins, the higher the iron/protein ratio the higher the iron dialysability, indicating that the extent of interaction between iron and protein, as well as influencing protein digestion, likely affects in-vitro iron availability.

Composition and calcium status of acid whey from pasteurized, UHT‐treated and in‐bottle sterilized milks

Whey extracts were obtained from pasteurized, UHT-treated and in-bottle sterilized milks. After acidic precipitation of casein the concentration of protein, NPN, lactose, lipid, calcium, magnesium and potassium was determined. Among the parameters examined, protein content was significantly reduced in the whey extracts from UHT-treated and in-bottle sterilized milks compared with that from pasteurized milk, while lactose content was increased. Calcium extracted in whey was at least 80% of total calcium of the milk. The total calcium to protein ratio of whey was increased as a function of the thermal treatment of milk, while ionic calcium was about 50% of total calcium in all whey extracts. In vitro protein digestibility was found to be significantly lower in whey from UHT-treated and in-bottle sterilized milks than in that from pasteurized milk. Parallel estimation of the percentage of ionic calcium and of the solubility of proteins in the pH range 2-10 indicated that calcium was not involved in the pH-dependent solubility of proteins extracted in the whey, the extent of solubility being essentially a function of the thermal treatment of milk. The results suggest that calcium was not responsible for the formation of soluble protein macroaggregates with impaired digestibility that are present in whey from milk subjected to heat treatment of increasing intensity.

Relationship between in vitro Fe and Zn dialysability and peptide composition of albumin and globulins extracted from cooked bean (Phaseolus vulgaris L.)

In vitro dialysability of iron, zinc and protein was determined from whole bean (Phaseolus vulgaris), albumin and globulin (G1, G2) after cooking. Albumin showed the highest iron, zinc, protein and phytic acid content. Cooking increased iron and protein dialysability only in whole bean and albumin. Compared to globulins, albumin also presented a higher in vitro protein digestibility and cystine chemical reactivity. HPLC analysis of peptides in dialysates of bean and protein fractions suggested that some aggregation occurred during dialysis. The percentage of amino acids in dialysed peptides was found to be different between albumin and globulins. The difference in iron and zinc dialysability between albumin and globulins seems to depend on the phytic acid content of the albumin fraction and the protein properties of globulins.