Optimization of the antioxidant capacity of thyme (Thymus vulgaris L.) extracts: Management of the convective drying process assisted by power ultrasound

The impact of ultrasound and steam blanching pre-treatments on the drying kinetics, energy consumption and selected properties of parsley leaves

“…Interestingly, when parsley was dried with higher microwave power, the type of pre-drying processing did not alter the chlorophyll's quantity significantly, with the exception of blanched and untreated leaves at 30°C. Beneficial effect of the US treatment on the biological components and their activity was also observed in the case of polyphenols in apple [22], antioxidant activity in thyme [25], chlorophyll a and b [31] and polyphenols contents in parsley leaves [29]. However, the character of influence on the chemical composition was always linked to the drying conditions and in some dried material a significant decomposition of the molecules was observed.…”

Drying Technologies: Vehicle to High-Quality Herbs

“…The optimization of drying conditions for each herb is strongly advised [21]. The most essential parameter influencing the end product quality of dried herbs is the temperature used, but air velocity has been shown to have a significant effect as well [22]; a combined effect of the two factors has also been reported [23]. In general, hot-air drying can lead to a drastic reduction in the quality of the end product compared to the original foodstuff [24]; principally high temperature causes the decomposition of bioactive ingredients and changes in colorful components [25].…”

“…The application of ultrasonic irradiation to assist drying has been used successfully for several fruits and vegetables such as carrots, persimmons, potatoes, eggplants [119][120][121][122] and herbs like thyme and basil [22,123]. The improvement in the end product quality is mainly founded on the A initial moisture ratio, BC constant rate drying, CD falling rate drying (phase I), DE falling rate drying (phase II) [128] Food Eng Rev increase in drying rate by the additional energy provided to water molecules via ultrasonic waves.…”

The impact of convective drying on the color, phenolic content and antioxidant capacity of noni (Morinda citrifolia L.)

“…This process is often used to decrease the chemical, enzymatic and microbiological reactions occurring in fruits and vegetables, representing a feasible and economical way to extend their shelf-life. However, a main drawback of drying is its undesirable effects on product quality indices, such as color changes and degradation of bioactive compounds, which depends of the severity on drying conditions (Rodríguez et al, 2013) and may lead to a reduced consumer acceptance (Larrosa et al, 2015). Pacheco-Aguirre et al (2014), Taghian Dinani et al (2014 and Rodríguez et al (2013) have used either empirical or mechanistic models to describe water transfer during convective drying of foodstuffs.…”

“…However, a main drawback of drying is its undesirable effects on product quality indices, such as color changes and degradation of bioactive compounds, which depends of the severity on drying conditions (Rodríguez et al, 2013) and may lead to a reduced consumer acceptance (Larrosa et al, 2015). Pacheco-Aguirre et al (2014), Taghian Dinani et al (2014 and Rodríguez et al (2013) have used either empirical or mechanistic models to describe water transfer during convective drying of foodstuffs. Empirical models include exponential or Page's equations (Taghian Dinani et al, The impact of convective drying on the color, phenolic content and antioxidant capacity of noni (Morinda citrifolia L.) 2014).…”