Monica Anese

Influence of processing on the antioxidant properties of fruit and vegetables

Abstract Nutritional factors are widely considered to be critical for human health. Overwhelming evidence from epidemiological studies indicate that diets rich in fruit and vegetables are associated with a lower risk of several degenerative diseases. These results have created a new perspective concerning the potential of diet in preventing serious diseases in the future. However, the health-promoting capacity of fruit and vegetables strictly depends on their processing history. This aspect has been generally neglected or scarcely considered in present nutritional and epidemiological studies. Processing is expected to affect content, activity and bioavailability of bioactive compounds. The aim of this article, therefore, is to review the effects of processing on the antioxidant properties of foods by means of a multidisciplinary approach. It is believed that the implications of this challenging and rapidly advancing area may contribute to enhanced industrial competitiveness as well as consumer health and well-being.

Loss and/or formation of antioxidants during food processing and storage

It is well known that natural antioxidants contained in foods are significantly lost during processing. Nevertheless it was recently demonstrated that thermal treatments can induce the formation of compounds with new antioxidant properties. This is the case of the Maillard reaction products (MRPs) whose presence as well as their potential effects have been scarcely investigated. In the present work the loss of natural antioxidants in relation to processing and the formation of MRPs with antioxidant activity were studied in different food systems such as tomato derivatives and coffee. Results showed that, although the concentration of natural antioxidants was significantly reduced as a consequence of the thermal treatments, the overall antioxidant properties of the food products were maintained or even enhanced by the development of MRPs.

Antioxidant properties of tomato juice as affected by heating

The changes in the overall antioxidant properties of tomato juice samples and model solutions as a consequence of heat treatments were studied. The antioxidant properties were evaluated both through the measurement of the chain breaking and the oxygen scavenging activities. While a decrease in the antioxidant potential was found for short heat treatments, a recovery of these properties was measured by prolonging heating times. Results suggested that the initial reduction in the overall antioxidant activity can be attributed not only to the thermal degradation of naturally occurring antioxidants but also to the formation of early Maillard reaction products (MRP) with pro-oxidant properties. The gain in antioxidant activity coincided with the formation of brown MRP. © 1999 Society of Chemical Industry

Antioxidant Properties of Ready-to-Drink Coffee Brews

The influence of some technological variables on the changes of the antioxidant capacity of ready-to-drink coffee brews was investigated. Results showed that, depending on the roasting degree as well as on the packaging conditions adopted, redox reactions, which can take place during storage, are responsible for significant changes in the overall antioxidant capacity of the product. In particular, the redox potential of air-packaged coffee brews, obtained from light- and medium-roasted beans, showed maximum values after 2 days of storage, which corresponded to a minimum in the chain-breaking activity, while, in the case of the dark-roasted sample packaged under ordinary atmosphere, both the redox potential and the chain-breaking activity showed a maximum around 2-3 days of storage. In contrast, in the absence of oxygen, the coffee brews maintained the initial reducing properties over all the storage time, although the radical-scavenging activity values changed in a way very similar to that of the air-packaged sample. These results suggested that the changes in the antioxidant properties of the coffee brews may be attributed to a further development of the Maillard reaction during storage.

Effects of drying processing on the Maillard reaction in pasta

The effect of low, high and very high drying temperatures on the development of the Maillard reaction in pasta was studied. In particular, an investigation was carried out into the influence of the different temperatures used on the development of colour, the formation of furosine and the changes in the chain breaking activity of pasta samples having different moisture contents as well as on the adsorption and desorption isotherms. Results showed that, depending on temperature, time and moisture conditions, pasta had antioxidant or pro-oxidant properties. The increase in the antioxidant potential was always associated with an increase in brown colour, while the pro-oxidant properties were observed in the early stages of the Maillard reaction.

Effect of ultrasound treatments of tomato pulp on microstructure and lycopene in vitro bioaccessibility

The influence of ultrasound treatments of tomato pulp on microstructure and lycopene in vitro bioaccessibility was investigated. To this purpose, samples were subjected to ultrasound at a frequency and amplitude of 24 kHz and 100 μm, respectively, for increasing lengths of time. Results showed that ultrasound was responsible for loss of tomato cell integrity, as well as a decrease in the degree of pectin esterification. In contrast, rheological measurements showed that ultrasonically treated tomato pulp had greater gel-like properties than an untreated sample. It was inferred that ultrasound promoted the formation of a new network due to hydrogen bonding and hydrophobic interactions among the de-esterified pectin molecules. Such a reinforcement of the tomato pulp structure resulted in a decrease in lycopene in vitro bioaccessibility of the ultrasonically treated tomato pulp, probably due to the fact that the presence of a stronger network may make lycopene less available to the digestion process.

Rapid mixed mode solid phase extraction method for the determination of acrylamide in roasted coffee by HPLC-MS/MS.

In this work, a rapid and reliable purification method based on a single mixed solid phase extraction (SPE) column, for the determination of acrylamide in roasted coffee by liquid chromatography-tandem mass spectrometry, was developed. Deuterium labelled d(3)-acrylamide was used as internal standard. Acrylamide was extracted by 10 mL of water and the extract purified by a single SPE column consisting of 0.5 g of an in-house prepared mixture of C18, strong cation (SCX) and anion exchange (SAX) sorbents in the ratio 2/1.5/1.5 (w/w/w). The amount of the three sorbents was optimised in order to eliminate the main interfering compounds present in coffee extracts, such as melanoidins, trigonelline, chlorogenic acids and caffeine. The SPE procedure was very simple and consisted of pushing 1 mL of an aqueous coffee extract through the SPE column followed by 1 mL of water which was collected for the analysis. The method was tested on six samples of roasted coffee of different composition and roasting level. The repeatability of the method, expressed as relative standard deviation (n=6), was lower than 5%. The recovery of acrylamide at three spiked levels ranged from 92% to 95%. The limits of detection (LOD) and quantitation (LOQ) were 5 and 16 μg kg(-1), respectively.

Evaluation of viscosities of amorphous phases in partially frozen systems by WLF kinetics and glass transition temperatures

Abstract The viscosities of concentrated solutions of glucose, fructose, sorbitol and xylitiol were measured by a falling sphere method. The measured viscosities were compared with those predicted by WLF kinetics from glass transition temperatures. Discrepancies between measured and predicted viscosities were found to be within an order of magnitude of 0.3 on log ϵ. Experimental data on sucrose solutions obtained from literature sources were also compared with WLF predicted values. The viscosities of the amorphous phases in frozen or partially frozen sucrose-, glucose-, fructose-, citric acid-, dimethyl sulfoxide-, polyvinylpyrrolidone- and glycerol-water systems were estimated by WLF kinetics and freezing temperatures. At equal sub-freezing temperature, the viscosities increased with the increasing of molecular weight. In addition, viscosity changes during devitrification and recrystallization of 60–70% sucrose solutions, which do not freeze upon cooling, were evaluated.

Polyphenoloxidase and peroxidase activity in partially frozen systems with different physical properties

Abstract Enzyme catalysed reactions can occur at significant rates at low temperatures, thus exerting a major control on the quality of frozen foods. The temperature-concentration effect in partially frozen systems can make enzyme reactions controlled by diffusion and thus rate limited by viscosity according to the Stokes–Einstein relation. Polyphenoloxidase (PPO) activity in sucrose, glycerol and fructose water media and (POD) activity in fructose and glycerol water media, were assayed spectrophotometrically from 20°C to −30°C. The media have at equal sub-freezing temperature marked differences in viscosities and others physical properties. For both enzymes, the activity data showed similar dependence on temperature and, above freezing, on the concentration of the media. A relation with the viscosity of the media at equal sub-freezing temperature was not evident. POD activity showed a “break” between −10°C and −20°C, suggesting a reversible conformational change. The temperature dependence of PPO rate constants were well described by both the Williams–Landel–Ferry ( r 2 =0.998) and the Arrhenius ( r 2=0.985) models. A hypothesis for the non conformity of the measured kinetics with the theoretical model is that in the temperature range considered the reactions are still activation controlled or in a transition zone, and should become diffusion limited only at lower temperatures and higher viscosities.

Monitoring dry-curing of S. Daniele ham by magnetic resonance imaging

S. Daniele hams were collected at different stages during dry-curing and submitted to magnetic resonance imaging (MRI) according to the acquisition Spin-Echo sequences T1 and T2. The intensity of the MR signals in the images of the Semimembranosus, Semitendinosus, Rectus femoris and Biceps femoris muscles of the hams was computed and expressed in grey levels. Muscles were also submitted to traditional analyses, including aw, soluble solids, sodium chloride, total and water soluble nitrogen. T1 and T2 MR signals well described the evolution of the phenomena occurring in the different muscles during dry-curing. MR signal acquired in T2 mode well correlated with traditional indicators in Semitendinosus, Rectus femoris and Biceps femoris muscles. Predictive models estimating the value of aw, moisture, salt content and proteolysis extent on the basis of the MR signal intensity were proposed.