Effect of microwave-assisted vacuum and hot air oven drying methods on quality characteristics of apple pomace powder

Abstract

Apple pomace, which makes up 20–30% of all processed apples, is an accessible source of bioactive ingredients that could be used in the food industry. A research of the impact of drying techniques on the quality characteristics of apple pomace powder was carried out to efficiently utilize this waste. The pomace was dried at 50 °C and 60 °C in a vacuum-assisted microwave dryer and an oven dryer, respectively. The different temperatures chosen for the drying of apple pomace were selected based on preliminary tests. Microwave drying resulted in reducing the drying time and improving the physicochemical, functional and morphological properties of the powder. The TPC (Total phenolic content) and AA (antioxidant activity) of pomace powder were found to be considerably influenced by the drying technique. Maximum TPC, DPPH and FRAP values observed for the apple pomace powder dried in the microwave were 5.21 ± 0.09 mg GAE/g, 93 ± 1% and 3.22 ± 0.04 µg/mg, respectively while as in oven drying, the values were 3.14 ± 0.06 mg GAE/g, 89 ± 1% and 2.22 ± 0.02 µg/mg. Microwave drying led to increasing bulk density (0.55 ± 0.01 g/cc), water hydration capacity (3.35 ± 0.09 mL/g), oil binding capacity (0.95 ± 0.04 g/g), solubility index (14.0 ± 0.9%), and emulsion capacity (60.0 ± 1.0%) of the powder. Lower values for bulk density (0.50 ± 0.01 g/cc), water hydration capacity (3.04 ± 0.08 mL/g), oil binding capacity (0.70 ± 0.03 g/g), solubility index (10.0 ± 0.8%), and emulsion capacity (48.0 ± 0.9%) were observed in oven-dried powder. Microwave drying resulted in a more disordered, crystalline and porous structure of apple pomace powder as compared to oven-dried powder as confirmed by SEM (Scanning electron microscopy) and XRD (X-ray diffraction). Microwave-dried powder also had a higher vitamin C content (20.00 ± 0.12 mg/100 mg) than oven-dried powder (12.53 ± 0.08 mg/100 mg). This study may be helpful in the preprocessing of apple pomace for bioconversion processes and extraction of valuable components from apple pomace. Graphical abstract

Effect of Ultrasound and Freeze‐Drying to Enhance the Extraction of Phenolic Compounds in Dragon Fruit Peels and Apply Them in Edible Starch‐Based Films

“…Ultrasound may have influenced the structure of the particles, with modifications to the cell walls of the dragon fruit peels during ultrasound [18], which could increase the solubility of the samples after FD. This pattern was also identified by Bhat et al [20] when examining the impact of different methods on the drying of apple pomace. They observed that samples subjected to more intense treatments demonstrated higher solubility and a less crystalline structure.…”

“…The particle size was analysed, in triplicate, as described in the method by Bhat et al [20]. A Zeta-sizer (Nano S, Malvern Instruments, Worcestershire, United Kingdom) was used for this purpose.…”

A Study on Quality Properties of Blackthorn (Prunus spinosa L.) Fruit Powder Obtained by Different Drying Treatments

“…According to the results, the highest ºh value was determined in the HAP sample, while the highest C* value was found in the FDP sample. In the literature, according to the results of color analysis of the powders obtained by applying different drying treatments to various fruit products, the common interpretation is that the drying applications significantly change the color coordinates [38,39]. However, this situation can turn into an advantage in order to give different colors in products intended to use these fruit powders obtained in the research.…”

New Strategy for Browning Prevention in Apple Pomace Processing and Toxicity Tested in a Rodent Model

“…Water holding capacity (WHC) was estimated by the method described previously with slight modifications. One gm of the debrowned AP was mixed with 30 mL water and incubated at room temperature (25 °C) for 24 h. Final weight of residual was measured and WHC was calculated using the below given formula as described W H C = W 2 − W 1 W 1 Here, W 1 = initial sample weight and W 3 = final weight of the sample.…”