Effects of Different Drying Methods on Drying Characteristics, Microstructure, Quality, and Energy Consumption of Apricot Slices.

An appropriate drying method is crucial for producing high-quality dried apricots. In this study, the effects of four drying methods, hot air drying (HAD), infrared drying (IRD), pulse vacuum drying (PVD), and vacuum freeze-drying (VFD), on the drying kinetics and physical and nutritional characteristics of apricot slices were evaluated. PVD required the shortest time (16.25 h), followed by IRD (17.54 h), HAD (21.39 h), and VFD (34.64 h). VFD resulted in the best quality of apricot slices, with the smallest color difference (ΔE = 13.64), lowest water activity (0.312 ± 0.015) and browning degree (0.35), highest color saturation (62.84), lowest hardness (8.35 ± 0.47 N) and shrinkage (9.13 ± 0.65%), strongest rehydration ability (3.58 ± 0.11 g/g), a good microstructure, and high nutrient-retention rates (ascorbic acid content: 53.31 ± 0.58 mg/100 g, total phenolic content: 12.64 ± 0.50 mg GAE/g, and carotenoid content: 24.23 ± 0.58 mg/100 g) and antioxidant activity (DPPH: 21.10 ± 0.99 mmol Trolox/g and FRAP: 34.10 ± 0.81 mmol Trolox/g). The quality of PVD-treated apricot slices was second-best, and the quality of HAD-treated apricot slices was the worst. However, the energy consumption required for VFD was relatively high, while that required for PVD was lower. The results of this study provide a scientific basis for the large-scale industrial production of dried apricots.

Wavelength-tunable spatiotemporal mode-locking in a large-mode-area Er:ZBLAN fiber laser at 2.8†µm.

We report a tunable spatiotemporally mode-locked large-mode-area Er:ZBLAN fiber laser based on the nonlinear polarization rotation technique. A diffraction grating is introduced to select the operating wavelength. Under the spectral and spatial filtering effects provided by the grating and spatial coupling respectively, stable ps-level spatiotemporally mode-locked pulses around 2.8 µm with a repetition rate of 43.4 MHz are generated. Through a careful adjustment of the grating, a broad wavelength tuning range from 2747 to 2797 nm is realized. To the best of our knowledge, this is the first wavelength-tunable spatiotemporally mode-locked fiber laser in the mid-infrared region.

High-energy femtosecond pulse generation from a hybrid mode-locked large-mode-area Er:ZBLAN fiber laser.

We report a hybrid mode-locked fiber laser at 2.8 µm based on a large-mode-area Er:ZBLAN fiber. Reliable self-starting mode-locking is achieved via the combination of nonlinear polarization rotation and a semiconductor saturable absorber. Stable mode-locked pulses with a pulse energy of 9.4 nJ and a pulse duration of 325 fs are generated. To the best of our knowledge, this is the highest pulse energy directly generated from a femtosecond mode-locked fluoride fiber laser (MLFFL) to date. The measured M2 factors are below 1.13, indicating a nearly diffraction-limited beam quality. Demonstration of this laser provides a feasible scheme for the pulse energy scaling of mid-infrared MLFFLs. Moreover, a peculiar multi-soliton mode-locking state is also observed, in which the time interval between the solitons varies irregularly from tens of picoseconds to several nanoseconds.