Attilio Visconti

Effects of different cooking methods on antioxidant profile, antioxidant capacity, and physical characteristics of artichoke.

In this study, the effects of three common cooking practices (i.e., boiling, steaming, and frying) on the artichoke phenolic compounds pattern were evaluated by LC-MS/MS analysis. The variation of carotenoids, antioxidant capacity, and artichoke physical properties after cooking was also investigated. The major phenolic compounds present in the raw sample were 5- O-caffeoylquinic and 1,5-di- O-caffeoylquinic acids; after cooking treatments, an increase of the overall caffeoylquinic acids concentration due to the formation of different dicaffeoylquinic acid isomers was observed. Steamed and fried samples showed similar patterns of dicaffeoylquinic concentrations, which were higher with respect to the boiled samples. On the other hand, all cooking practices, particularly frying, decreased flavonoid concentration. The antioxidant capacity of cooked artichokes, measured by three different assays, enormously increased after cooking, particularly after steaming (up to 15-fold) and boiling (up to 8-fold). The observed cooking effect on the artichoke antioxidant profile is probably due to matrix softening and increased extractability of compounds, but the increase of antioxidant capacity is much higher than the increase of antioxidant concentration. These results suggest that some common cooking treatments can be used to enhance the nutritional value of vegetables, increasing bioaccessibility of health-promoting constituents.

Identification of a β-lactoglobulin lactosylation site

Abstract Thermal treatment of milk leads to non-enzymatic glycosylation of proteins through Maillard reaction. Free NH2 groups of basic amino acids react with the reducing carbonyl group of lactose forming the so-called Amadori products. Electrospray mass spectrometry analysis shows that β-lactoglobulin (β-LG), the major whey protein, undergoes lactosylation under industrial thermal treatment. In order to investigate the specificity of reactive sites for lactose binding the analysis of trypsin hydrolysates of β-LG isolated from different industrial milks was performed. Results demonstrate that Lys-100 is a preferential lactosylation site of β-LG during industrial milk treatment. These results were confirmed by an analysis of the three-dimensional model of the protein which showed that Lys-100 had the highest solvent accessibility and proximity to another amino group making Lys-100 the best candidate to lactosylation. Lys-47, previously identified by other authors, showed a good proximity to another Lys residue, but an intermediate level of exposition to solvent.

Chemical profile and sensory properties of different foods cooked by a new radiofrequency oven

Radio frequency (RF) heating has been used for numerous applications in the food industry such as baking, thawing or pasteurisation. It reduces cooking time, and it helps to retain acceptable food colour and texture. In this paper, chemical and sensory data obtained from broccoli, potatoes, salmon and cocoa cakes cooked using an innovative RF oven were reported. The oven has an algorithm able to monitor the energy feedback from the cavity and to adjust the energy output accordingly. The different foods were cooked to the same end point and the concentration of phytochemicals, vitamins and acrylamide were assessed. Results demonstrated that RF oven preserved ascorbic acid and increased glucosinolates concentration in broccoli and it decreased the formation of acrylamide in roasted potatoes more than 50%. The total amount of vitamins B was 30% and 50% higher in RF cooked salmon than conventionally cooked salmon prepared at 55 and 75°C, respectively.

Nutritional Quality of Sous Vide Cooked Carrots and Brussels Sprouts

Phytochemicals (carotenoids, phenolic compounds, and ascorbic acid) and antioxidant capacity (measured by TEAC, FRAP, and TRAP assays) were evaluated on carrots and Brussels sprouts sous vide processed and then stored refrigerated for 1, 5, and 10 days and compared with the corresponding raw and oven-steamed products. Data showed that sous vide cooked carrots had higher amounts of carotenoids, phenolic compounds, and ascorbic acid than steamed products, and only a slight decrease of phenolic compounds was recorded during sous vide storage. Contrasting results were obtained on sous vide processed Brussels sprouts: higher carotenoid amounts and TEAC and TRAP values and lower phenolic compounds, ascorbic acid, and FRAP values were exhibited by sous vide in comparison with steamed samples. Phytochemicals and TAC also decreased during Brussels sprout sous vide storage with the exception of carotenoids. The results of this study demonstrated that sous vide preparation can preserve and/or enhance the nutritional quality of carrots, which remain a good source of carotenoids also after long refrigerated storage, whereas the same treatment could be recommended as an alternative to oven-steaming in the preparation of Brussels sprouts for short-term maintenance to avoid a large ascorbic acid depletion.

Impact of the industrial freezing process on selected vegetables -Part II. Colour and bioactive compounds

In the present study, the impact of the different steps (i.e. blanching, freezing, storage following the industrial freezing process and the final cooking prior to consumption) of the industrial freezing process was evaluated on colour, chlorophylls, lutein, polyphenols and ascorbic acid content of asparagus, green beans and zucchini. In addition, the domestic boiling of raw samples was compared with the boiling of frozen storage vegetables. Results showed that the blanching treatment retained phytochemicals in all studied green vegetables and the frozen storage up to 2months did not negatively affected phytochemicals, in particular lutein and flavonoids in almost all samples. On the contrary, colour significantly changed during blanching and frozen storage. The changes of b* (yellowness) and the shift of H° (hue angle) were not coherent with the increase of pheophytin. In addition, the greenness (-a*) was found to increase with the exception of boiled samples in all vegetables. Generally, in boiled frozen vegetables there was a better or comparable retention of bioactive compounds with respect to raw ones, and this was especially true for green beans and zucchini. Colour changes after cooking did not exhibit the same trends among vegetables, being more remarkable for frozen asparagus in comparison with those boiled from raw, but overall comparable for green beans and zucchini. In conclusion, the overall results of the present study suggest that, when the industrial freezing process is well performed, the boiled frozen vegetables do not have a lower nutritional value than the fresh ones.

Raman spectroscopy application in frozen carrot cooked in different ways and the relationship with carotenoids

BACKGROUND Raman spectroscopy, in its confocal micro-Raman variation, has been recently proposed as a spatially resolved method to identify carotenoids in various food matrices, being faster, non-destructive, and avoiding sample extraction, but no data are present in the literature concerning its application to the evaluation of carotenoid pattern changes after thermal treatment of carrots. RESULTS The effect of three cooking methods (i.e. boiling, steaming and microwaving) was evaluated on frozen carrot, comparing changes on carotenoid profiles measured by means of Raman spectroscopy with their high-performance liquid chromatographic determination and colour. A more pronounced detrimental effect on carotenoids was detected in steamed carrots, in accordance with colour data. Conversely, boiling and, to a lesser extent, microwaving caused an increase in carotenoid concentration. Cooking procedures affected the Raman spectral features of carotenoids, causing a shift of vibration frequencies towards a higher energy, increase in the spectral baseline and peak intensities as well as a broadening of their width, probably in relation to the thermal degradation of longer carotenoids (i.e. the all-trans form) and the isomerization process. In particular, steamed samples showed a significantly higher increase of centre frequency, in accordance with a more pronounced isomerization and changes in colour parameters. CONCLUSION This work showed that the evolution of Raman spectral parameters could provide information on carotenoid bioaccessibility for carrots cooked using various methods. This paves the way for a future use of this technique to monitor and optimize cooking processes aimed at maximizing carotenoid bioaccessibility and bioavailability.