Ultrasound‐assisted ascorbic acid solution pretreated hot‐air drying improves drying characteristics and quality of jujube slices

Abstract

BACKGROUND The effective hot‐air drying of foods such as jujube requires an effective green pretreatment alternative to chemical pretreatments. Jujube slices were pretreated using 5 and 10 mg mL−1 ultrasound‐assisted vitamin C (UVC) for 10, 20, and 30 min, followed by hot‐air drying. RESULTS Ultrasound‐assisted vitamin C pretreatment for 10, 20, and 30 min modulated the characteristics of fresh jujube slices such as water loss (from −28.25% to −25.52% after 30 min of UVC pretreatment), solid gain (from −31.68% to −26.82% after 30 min of UVC pretreatment), loss of total and reducing sugars (from 200.25 mg and 34.88 mg to 287.14 mg and 4.71 mg, respectively, after 30 min of UVC pretreatment), total soluble solids (from 76.32 oBrix to 82.08 oBrix), and water diffusivity (from 9.01 × 10−10 m2 s−1 to 6.71 × 10−10 m2 s−1). These characteristics were associated with altered surface morphology and improved drying characteristics. The UVC pretreatment preserved an acceptable reddish‐yellow or orange‐like color during hot‐air drying and reduced the browning index from 26.3 optical density (OD)/g DM to 23.25 OD/g dry mass basis (DM), which was connected with reduced 5‐hydroxymethylfurfural (HMF) content. On the other hand, the proportions of bioactive components such as vitamin C increased from 1.05 mg g−1 DM to 9.02 mg g−1 DM, phenolics increased from 12.8 mg gallic acid equivalent (GAE)/g DM to 17.5 mg GAE/g DM, flavonoids increased from 4.0 mg rutin equivalent (RE)/g DM to 4.4 mg RE/g DM, and procyanidin content increased from 2.0 mg catechin equivalents (CE)/g DM to 2.9 mg CE/g DM in UVC pretreated jujube slices, which had a positive association with increased antioxidant activity – for example, 2,2'‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid (ABTS) increased from IC50 22.5 mg DM/mL to 8.0 mg DM/mL, 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) changed from IC50 36.5 mg DM/mL to 9.5 mg DM/mL, and ferric reducing antioxidant power (FRAP) increased from 2.0 mg vitamin C equivalent (VCE)/g DM to 11.9 mg VCE/g DM). CONCLUSION The data indicated that UVC can be used as a promising pretreatment method for improving the hot‐air drying characteristics and the quality of jujube slices. © 2023 Society of Chemical Industry.

Profiling the Major Aroma-Active Compounds of Microwave-Dried Jujube Slices through Molecular Sensory Science Approaches

“…The descriptors were selected from the words described by 10 professional reviewers, and words with 80% or more of the votes were counted as evaluation words. Subsequently, organoleptic characteristic descriptors were quantified using five sensory attributes (caramel flavor, roasted sweet flavor, bitter, burnt, and jujube-ID) [ 5 ]. The training primarily focused on sensory and semiquantitative descriptive analysis, following the ISO international standard (8586-1, 1993).…”

“…Among various processed jujube products, dried jujube slices are the most favorable, with the best taste, rich nutritional value, and easy to eat. Additionally, jujube slices provide good economic benefits and broad prospects for development [ 5 ]. Dried jujube slices are mostly prepared—including cleaning, coring, and slicing—from naturally dried jujube (about 30% moisture content).…”

Ultrasound treatment alleviates external pericarp browning and improves fruit quality of pomegranate during storage

“…18 Ultrasound technology can inactivate microorganisms and improve the quality of horticultural products during storage. 15,[19][20][21][22] Moreover, ultrasound treatment delayed the browning of litchi pericarp during storage at 28 °C, 19 and fresh-cut lotus roots during cold storage combined with cysteine. 23 In summary, ultrasound can extend the storage life of fresh fruit and vegetables, and reduce microbiological hazards.…”

“…Reports show increasingly that ultrasound enhances the microbiological safety of fresh horticultural produce by removing bacterial adhesion on green peppers and melons, 15 inhibiting the growth and the total number of colonies of mold and yeast on fresh‐cut cucumber with modified atmospheric packaging, 13 removing five pesticides from rape and grape, 16 and reducing mold growth on strawberry, 17 and the decay rate of white nectarine 18 . Ultrasound technology can inactivate microorganisms and improve the quality of horticultural products during storage 15,19‐22 . Moreover, ultrasound treatment delayed the browning of litchi pericarp during storage at 28 °C, 19 and fresh‐cut lotus roots during cold storage combined with cysteine 23 .…”