Impact of fluorescent lighting on the browning potential of model wine solutions containing organic acids and iron

Response Surface Methodology Approach to Evaluate the Effect of Transition Metals and Oxygen on Photo-Degradation of Methionine in a Model Wine System Containing Riboflavin

A Box-Behnken experimental design was implemented in model wine (MW) to clarify the impact of copper, iron, and oxygen in the photo-degradation of riboflavin (RF) and methionine (Met) by means of response surface methodology (RSM). Analogous experiments were undertaken in MW containing caffeic acid or catechin. The results evidenced the impact of copper, iron, and oxygen in the photo-induced reaction between RF and Met. In particular, considering a number of volatile sulfur compounds (VSCs) that act as markers of light-struck taste (LST), both transition metals can favor VSC formation, which was shown for the first time for iron. Oxygen in combination can also affect the concentration of VSCs, and a lower content of VSCs was revealed in the presence of phenols, especially caffeic acid. The perception of "cabbage" sensory character indicative of LST can be related to the transition metals as well as to the different phenols, with potentially strong prevention by phenolic acids.

Physicochemical and Active Properties of Gelatine-Based Composite Gels Loaded with Lysozyme and Green Tea Polyphenols

Research background

The use of gel-based systems as a novel method for the delivery of natural antimicrobial, antioxidant and bioactive compounds is a developing innovative solution for the food industry. This research aims to develop multifunctional active edible gels based on gelatine and its composites with improved mechanical properties.

Experimental approach

Antilisterial and bioactive composite gels showing different physical and active properties from classical gelatine gel were developed by loading lysozyme and green tea extract into gelatine/starch and gelatine/wax composite gels. Mechanical properties, swelling profiles, colour, release profiles, and antimicrobial and bioactive properties of the gels were characterised.

Results and conclusions

Gelatine/wax gels showed 1.3- to 2.1-fold higher firmness and cutting strength than gelatine and gelatine/starch composite gels that had similar firmness and cutting strengths. Work to shear of both composite gels was 1.4- to 1.9-fold higher than that of gelatine gel. The gelatine/starch gel showed the highest water absorption capacity. Green tea extract reduced soluble lysozyme in all gels, but composite gels contained higher amount of soluble lysozyme than gelatine gel. All the gels with lysozyme inhibited Listeria innocua growth in the broth media, while green tea extract showed antilisterial activity only in gelatine/wax gels. Gels with green tea extract showed antioxidant, antidiabetic (α-glucosidase and α-amylase inhibition), antihypertensive (angiotensin-converting enzyme inhibition) and antiproliferative activities (on Caco-2 human colon carcinoma cells). However, gelatine and gelatine/wax gels showed the highest antioxidant and antidiabetic activity. The gelatine/wax gels prevented phenolic browning, while green tea extract in other gels showed moderate or extensive browning.

Novelty and scientific contribution

This work clearly showed the possibility of improving mechanical properties and modifying water absorption and controlled release profiles of gelatine gels using gelatine/starch and gelatine/wax composites. The novel composite gels reduced browning of incorporated polyphenols and showed antilisterial and bioactive properties.

Light-Struck Taste in White Wine: Protective Role of Glutathione, Sulfur Dioxide and Hydrolysable Tannins

Light exposure of white wine can cause a light-struck taste (LST), a fault induced by riboflavin (RF) and methionine (Met) leading to the formation of volatile sulfur compounds (VSCs), including methanethiol (MeSH) and dimethyl disulfide (DMDS). The study aimed to investigate the impact of different antioxidants, i.e., sulfur dioxide (SO2), glutathione (GSH) and chestnut tannins (CT), on preventing LST in model wine (MW) and white wine (WW), both containing RF and Met. Both MW and WW samples were added with the antioxidants, either individually or in different combinations, prior to 2-h light exposure and they were stored in the dark for 24 months. As expected, the light induced the degradation of RF in all the conditions assayed. Met also decreased depending on the antioxidants added. The presence of antioxidants limited the formation of LST as lower concentrations of VSCs were found in both MW and WW samples. In the latter matrix, neither MeSH nor DMDS were detected in the presence of CT, while only DMDS was found in WW+GSH, WW+SO2+GSH and WW+CT+SO2 samples at a concentration lower than the perception thresholds. Considering the antioxidants individually, the order of their effectiveness was CT ≥ GSH > SO2 in WW under the adopted experimental conditions. The results indicate tannins as an effective enological tool for preventing LST in white wine and their use will be further investigated in different white wines under industrial scale.

Effects of light exposure on chemical and sensory properties of storing Meili Rosé wine in colored bottles

The changes of chemical compositions and sensory characteristics of Meili rosé wine in flint, antique green and amber bottles were studied under continuous illumination for 160 days in two light sources (white fluorescent light, UV light). The results showed that light exposure caused significant changes in free sulfur dioxide content, Fe(III):Fe(II) ratio and Malvidin-3-O-glucoside content, responsible for the accelerated color evolution of Meili rosé wine during bottle storage. Some notable aroma-related changes were also observed for sensory characteristics, particularly for wines in flint bottles, boiled-like odor and oxidized odor appeared. Bottle color played a key role in preventing rosé wine from light exposure, following the order: amber bottle > green bottle > flint bottle. Besides UV light, white fluorescent light did have negative effects on rosé wine quality, considering its ubiquitous presence and long-term exposure in practice. The underlying mechanisms related to photochemical reactions in wine were further discussed.

Il difetto di luce nel vino bianco: Effetto ed evoluzione nel corso della conservazione

L'esposizione del vino bianco ad una radiazione luminosa impatta negativamente sulle caratteristiche sensoriali. Tale condizione può causare la comparsa di un'alterazione, nota come difetto di luce, causata dalla formazione di composti solforati, quali metantiolo (MeSH) e dimetildisolfuro (DMDS). Le reazioni indotte dalla luce originano dalla riboflavina (RF), un composto fotosensibile, e dalla metionina (MET). I trattamenti del vino bianco con bentonite o carbone attivo sono efficaci per rimuovere parte della RF e l'aggiunta al vino di tannini idrolizzabili limita la comparsa del difetto di luce in soluzione modello. Non è stata ancora chiarita l'evoluzione del difetto di luce nel vino bianco durante la shelf-life. In questo studio sono stati valutati gli effetti dei fenomeni foto-indotti in vino bianco dopo 24 mesi di conservazione. Il vino è stato addizionato di RF, MET e antiossidanti, quali glutatione, anidride solforosa e tannino di castagno, singolarmente ed in combinazione, esposto alla luce e conservato al buio. Come atteso, la RF è degradata in seguito all'esposizione alla fonte luminosa in tutte le condizioni saggiate. La diminuzione di MET è compresa nel range 21–38% in funzione degli antiossidanti aggiunti che, quando aggiunti singolarmente, limitano la formazione del difetto di luce come dimostra il minore livello di MeSH e DMDS presenti. I dati ottenuti suggeriscono che l'impiego di tannini da legno può essere un efficace strumento per limitare la comparsa del difetto di luce anche nel vino bianco.