1,721,102 research outputs found
Kinetics of quality degradation during storage of monovarietal extra virgin olive oils
No full textIntroduction. Lipophilic derivatives of olive secoiridois (namely, the dialdehydic form of decarboxymethyl oleuropein aglycone, the isomer of oleuropein aglycone, the dialdehydic form of decarboxymethyl ligstroside aglycone, and the isomer of ligstroside aglycone) are present in extra virgin olive oil (EVOO) due to the hydrolysis of their glycosidic precursor catalysed by endogenous glycosidases during the crushing of olive fruit. These compounds as well as alpha-tocopherol have received considerable interest due to their potential health effects, and could be used as indices to evaluate EVOO quality in addition to those established by the EU Regulations (1). Here we report on the kinetics of autoxidation and hydrolytic processes that occur during storage of EVOO, and their effects on the antioxidant content. The aim of this study was to determine whether the potential properties of EVOO antioxidants are maintained or lost during the commercial life of the product.
Materials and methods. EVOOs of the Picual, Arbequina, Taggiasca, and Colombaia cultivars were obtained from industrial oil mills. EVOOs were stored under dark, in closed-bottles (10% head-space), at 25-40oC for a period of 8 months. For each cultivar six bottles were taken from the incubator at scheduled times (monthly) for the analysis of acidity, peroxide number, spectroscopic indices K232 and K270, alpha-tocopherol, phenolics, and antioxidant activity (2).
Results. Four monovarietal EVOOs with different fatty acid compositions and antioxidant contents were chosen to define the extent of antioxidant degradation during storage. Secoiridoids, alpha-tocopherol, and the antioxidant activity decreased in all EVOOs following pseudo-first order kinetics. Oleuropein derivatives were less stable than the corresponding ligstroside derivatives and alpha-tocopherol. Hydroxytyrosol and tyrosol increased during storage as a result of secoiridoid hydrolysis. However, the increase of simple phenolics was lower than the decrease of their precursors, indicating that degradation occurred via both hydrolysis and oxidation. Free acidity, peroxide value, and the spectroscopic indices in the UV region increased following pseudo-zero order kinetics.
The rate constants for quality indices degradation were obtained, and the time to reach the limits established by EU Regulation was calculated. In all EVOOs K232 was the first parameter that exceeded the legal limit. It was found that when EVOOs attained the this latter threshold the residual antioxidant activity was more than 60% with respect to the initial value. These data led to the conclusion that the beneficial properties of EVOOs due to antioxidant activity can be maintained throughout their commercial lives.
References
1. V. Lavelli (2002) J Agric. Food Chem. 50, 26, 7704-7708.
2. V. Lavelli, G. Fregapane, M.D. Salvador (2006), J Agric. Food Chem. 54, 8, 3002-3007
Cosmetica nell'era della bioeconomia: prevenzione dell'invecchiamento cutaneo mediante agenti antiglicanti recuperati dai residui di vinificazione
No full textLa glicazione proteica (reazione di Maillard) è un processo chiave alla base dell’invecchiamento cutaneo, accelerato da condizioni patologiche (diabete), dal fumo e dall’ esposizione a raggi solari e all’inquinamento. Precedenti ricerche condotte presso UNIMI hanno mostrato che i fenoli di campioni di bucce d’uva, recuperate dai residui di vinificazione hanno elevatissimi proprietà antiglicanti essendo in grado di disattivare i composti dicarbonilici, intermedi della reazione molto reattivi (rif. 1-2), come successivamente confermato in uno studio in collaborazione con un partner spagnolo (rif. 3). Considerando diverse fonti di sostanze antiglicanti a confronto è stata costruita una scala di efficacia che ha mostrato il seguente ranking: bucce di uva rossa > bucce di uva bianca >> estratti fenolici commerciali >>> aminoguanidina, composto di riferimento. Considerando che i residui di vinificazione sono ampiamente disponibili a basso costo, si può concludere che queste matrici potrebbero essere utilizzate per lo sviluppo di efficaci prodotti cosmetici antiglicanti
Cinetica di variazione del potere antiossidante dell’olio extra vergine di oliva in fase di stoccaggio
No full textThe degradation kinetics of antioxidant activity, free acidity, peroxide value, and spectroscopic indices in the UV region of monovarietal extra virgin olive oils (cv. Taggiasca) were studied during 8 months of storage in closed bottles, in the dark, at 25-40°C. Results showed that the secoiridoids and α-tocopherol decreased following pseudo-first order kinetics, and the dialdehydic form of decarboxymethyl oleuropein aglycone was the most unstable. The antioxidant activity, as evaluated in vitro by using the 2,2-diphenyl-1-picrylhydrazyl radical, decreased following a pseudo-first order kinetic. Free acidity, peroxide value, and the spectroscopic indices in the UV region increased following pseudo-zero order kinetics, and K232 was the first parameter that exceeded the upper established limit for extra virgin olive oil. A time-temperature plot was used to represent the behaviour of all quality indices during storage. This plot reveals the operating conditions in which the quality of product may be maintained
Le modalità di trasformazione e la sicurezza alimentare
No full textL’esigenza di procurarsi il cibo ha contribuito allo sviluppo dell’ingegno e alla storia dell’uomo. Partendo dall’insegnamento di alcune specie di scimmie, che hanno inventato strumenti e processi alimentari, rifletteremo su come i concetti antagonisti di “bene” e “male” si applicano agli alimenti e ci focalizzeremo sul rischio alimentare, analizzandone il significato.
Discuteremo due modelli di sicurezza alimentare: il primo descrive la strategia con cui la Comunità Europea ha impostato la gestione del rischio alimentare; il secondo è globale, prende in considerazione l’intero pianeta e illustra come le sfide sociali del futuro coinvolgono il sistema alimentare. Infine ipotizzeremo cosa ci sarà nel “pic-nic" di domani”
A comparative study of the antioxidant activity of tomato derivatives by enzyme- and metal-catalyzed reactions
No full text
Comparison of the antioxidant activities of extra virgin olive oils
No full textThe phenol content and antioxidant activity of extra virgin olive oils (EVOOs) differing in their origins
and degradation degrees were studied. The o-diphenolic compounds typical of olive oil, namely, the oleuropein derivatives hydroxytyrosol (3,4-dihydroxyphenylethanol, 3,4-DHPEA), the dialdehydic form of elenolic acid linked to 3,4-DHPEA (3,4-DHPEA-EDA), and an isomer of oleuropein aglycon (3,4-DHPEA-EA), were analyzed by HPLC. The antioxidant activity was studied by (a) the xanthine oxidase (XOD)/xanthine system, which generates superoxide radical and hydrogen peroxide; (b) the
diaphorase (DIA)/NADH/juglone system, which generates superoxide radical and semiquinonic radical; and (c) the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) test. Results showed that EVOOs with a low degradation level (as evaluated by acidity, peroxide number, and spectroscopic indices K232, K270, and deltaK according to the EU Regulation) had a higher content of 3,4-DHPEA-EDA and a lower content of 3,4-DHPEA than oils having intermediate and advanced degradation levels. EVOOs with a low degradation degree were 3-5 times more efficient as DPPH scavengers and 2 times more efficient as inhibitors of the XOD-catalyzed reaction than oils with intermediate and advanced degradation levels. The DIA-catalyzed reaction was inhibited by EVOOs having low or intermediate degradation levels but not by the most degraded oils
Indici analitici della qualità dell'olio extra vergine di oliva. In: Prospettive della qualità, della normativa e del business nel settore dell'olio di oliva
No full textLa definizione della qualità nutrizionale di un alimento non può mai essere assoluta, in quanto le conoscenze sui bisogni alimentari degli individui sono in continua evoluzione.
L'intervento riporta sinteticamente i più recenti studi sulle proprietà nutrizionali dell'olio extra vergine di di oliva e discute i parametri numerici che ne rappresentano la qualità
Antioxidant activity of minimally processed red chicory (Cichorium intybus L.) evaluated in xanthine oxidase-, myeloperoxidase-, and diaphorase-catalyzed reactions
No full textMinimally processed red chicory products (Cichorium intybus L. var. silvestre) were studied for their polyphenol content and antioxidant activity evaluated by using the synthetic 2,2-diphenyl-1-(2,4,6- trinitrophenyl)hydrazyl radical and three model reactions catalyzed by relevant enzymatic sources of reactive oxygen species, namely, xanthine oxidase, myeloperoxidase, and diaphorase. Products were analyzed at the time of production and after storage at 4 °C within either a gas permeable film or a gas barrier film. The antioxidant activity and contents of hydroxycinnamic acids and flavonoids
decreased by less than 20% during storage of the minimally processed red chicory products. Total phenolics were significantly correlated with the antioxidant activity evaluated with both the synthetic radical and the enzyme-catalyzed reactions. On a molar basis, red chicory phenolics were as efficient as the reference compound Trolox in scavenging the synthetic radical. However, red chicory phenolics had a much higher inhibitory activity than Trolox in the model enzymatic systems
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