Insight into the evolution of flavor compounds during cooking of common beans utilizing a headspace untargeted fingerprinting approach.

Beans age during storage leading to prolonged cooking times. Chemical reactions that occur during cooking lead to volatile production and flavor generation. Whereas few studies profiled the volatile fingerprint of either non-cooked beans or beans cooked for a specific time, this study explored the evolution of volatiles through headspace fingerprinting of beans cooked at 95 °C to different extents. The influence of aging of beans on this evolution was investigated. Cooking time clearly influenced the evolution of volatiles for both fresh (non-aged) and aged beans. Aged beans exhibited more discriminant compounds than fresh beans regardless of texture considerations due to differences in pre-history of the beans. Strecker aldehydes, sulphur compounds and furan compounds were identified as marker compounds and were linked to mainly lipid oxidation and Maillard reactions. In conclusion, both aging prior to cooking and the cooking process itself largely influence the evolution of volatile compounds during cooking.

Quality changes of pasteurised orange juice during storage: A kinetic study of specific parameters and their relation to colour instability.

In view of understanding colour instability of pasteurised orange juice during storage, to the best of our knowledge, this study reports for the first time in a systematic and quantitative way on a range of changes in specific quality parameters as a function of time and as well as temperature (20-42 °C). A zero-order (°Brix, fructose, glucose), a first-order (vitamin C), a second-order (sucrose) and a fractional conversion model (oxygen) were selected to model the evolution of the parameters between parentheses. Activation energies ranged from 22 to 136 kJ mol(-1), HMF formation being the most temperature sensitive. High correlations were found between sugars, ascorbic acid, their degradation products (furfural and HMF) and total colour difference (ΔE(∗)). Based on PLS regression, the importance of the quality parameters for colour degradation was ranked relatively among each other: the acid-catalysed degradation of sugars and ascorbic acid degradation reactions appeared to be important for browning development in pasteurised orange juice during ambient storage.

Quality changes of pasteurised mango juice during storage. Part I: Selecting shelf-life markers by integration of a targeted and untargeted multivariate approach.

For the first time, a multivariate approach combining targeted and untargeted data was used to obtain insight into quality changes in pasteurised mango juice (cv. 'Totapuri') as a function of storage (42°C for 8weeks). Mango juice samples were formulated with addition of different potential precursors for different quality-related chemical reactions: ascorbic acid, citric acid and sugars. Control (diluted mango puree with water), ascorbic acid-enriched (AA250 and AA500), citric acid-enriched (CA, CA+AA250 and CA+AA500) and sugar-enriched (S) samples were characterised for a range of targeted quality parameters as well as for a volatile fingerprint (untargeted). Selection of shelf-life markers or quality parameters significantly changing during shelf-life was performed over all formulations as well as per mango juice formulation. Our study showed that a common trend over all formulations was observed for colour values (VID>│0.90│), while specific shelf-life markers were selected for each formulation. In acidified mango juice samples (CA, CA+AA250, CA+AA500), more terpene oxides were selected compared to other formulations. In ascorbic acid-enriched samples (AA250, AA500, CA+AA250, CA+AA500), furfural and ascorbic acid were significantly changing during shelf-life. It seems that the reaction pathways for compounds being formed or degraded upon shelf-life are clearly affected by the acidity level.

Quality changes of pasteurised mango juice during storage. Part II: Kinetic modelling of the shelf-life markers.

The present work shows the potential of the integrated fingerprinting-kinetics approach in evaluating shelf-life changes of pasteurised mango juice (cv. 'Totapuri'). Seven mango juice formulations (i.e. control (mango puree and water), ascorbic acid-enriched (AA250 and AA500), citric acid-enriched (CA, CA+AA250 and CA+AA500) and sugar-enriched (S) samples) were pasteurised and stored at 42°C for 8weeks. In this part, the kinetics of the shelf-life markers selected from the multivariate fingerprinting approach was modelled. Changes in selected targeted parameters could be best described by a zero-order (colour values, °Brix, furfural, HMF), a first-order (ascorbic acid), a fractional conversion (fructose, glucose, oxygen) and a second-order model (sucrose). Differences in the rate constant were observed, with faster ascorbic acid degradation and furfural formation in AA-enriched samples and faster hydrolysis of sugars and HMF formation in CA-enriched samples compared to control samples. To describe changes in selected volatiles (terpenes, sulphur compounds, acids, ketones and esters), different kinetic models were selected. Two trends were observed: changes as affected by different mango juice formulations (e.g., faster reaction in CA-enriched samples or in a lower pH condition) and changes irrespective of the formulations. Referring to the literature, in general, acid-catalysed reactions, ascorbic acid degradation and oxidation reactions are the main reactions responsible for the observed quality changes in stored mango juice.

Study of chemical changes in pasteurised orange juice during shelf-life: A fingerprinting-kinetics evaluation of the volatile fraction.

The current work used fingerprinting-kinetics for the first time to monitor shelf-life changes in a low-pH, pasteurised, shelf-stable product, more particular in orange juice. Orange juice samples were stored as a function of time at four different storage temperatures (20, 28, 35 and 42°C). To obtain insight into chemical changes in the volatile food fraction, samples were fingerprinted with headspace GC-MS. The objectives of this work were twofold: (i) to identify major chemical changes of pasteurised orange juice during shelf-life and (ii) to study the kinetics of selected shelf-life compounds in the context of accelerated shelf-life testing (ASLT). At 20°C, changes in terpenes and a decrease in aldehydes were observed. Oxides and sulphur compounds increased and esters decreased at increased storage temperatures (at 28°C and above). Concerning ASLT, four volatile compounds had clear temperature and time dependent kinetics within the investigated temperature range.

Colour and carotenoid changes of pasteurised orange juice during storage.

The correlation of carotenoid changes with colour degradation of pasteurised single strength orange juice was investigated at 20, 28, 35 and 42°C for a total of 32 weeks of storage. Changes in colour were assessed using the CIELAB system and were kinetically described by a zero-order model. L(∗), a(∗), b(∗), ΔE(∗), Cab(∗) and hab were significantly changed during storage (p<0.05). Activation energies for all colour parameters were 64-73 kJ mol(-1). Several carotenoids showed important changes and appeared to have different susceptibilities to storage. A decrease of ß-cryptoxanthin was observed at higher temperatures, whereas antheraxanthin started to decrease at lower temperatures. Depending on the time and temperature, changes in carotenoids could be due to isomerisation reactions, which may lead to a perceptible colour change. Although the contribution of carotenoids was recognised to some extent, other reactions seem of major importance for colour degradation of orange juice during storage.