Effects of osmotic pretreatment and frying conditions on quality and storage stability of vacuum‐fried pumpkin chips

Osmotic and convective hot air drying of sweet gourd

Kinetics of osmotic dehydration (OD) and insights into the effect of salt concentration (5%, 10%, 15%, 20%), drying temperature (50 ∘ C, 60 ∘ C, 70 ∘ C), and sample thickness (4 mm, 6 mm, 8 mm) on the drying kinetics of sweet gourd of two varieties (SGV-1 and SGV-2) were investigated based on the Fick's second law of diffusion model. Quality attributes (chemical and organoleptic) of biscuit formulated with osmotic dehydrated sweet gourd powder were assessed. Results showed that, significant changes occurred during the first 2 h of process where mass transfer kinetics were increased with increasing salt concentration. With increasing time, drying rate was proportional to the temperature, inversely proportional to the sample thickness as well as salt concentration. Moreover, sweet gourd variety has shown impact on formulated products quality and consumer acceptability which could serve as a ground to diversify the use of sweet gourd towards industrial application.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01193-x.

Reduction of oil uptake in vacuum fried Pleurotus eryngii chips via ultrasound assisted pretreatment

The reduction of oil uptake in vacuum-fried Pleurotus eryngii chips by ultrasound assisted pretreatment was investigated regarding the pore structure changes. Pore structure of P. eryngii chips with four pretreatments, such as blanching, blanching + osmosis, blanching + ultrasound and blanching + ultrasound assisted osmosis was determined by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). In addition, the quality parameters of vacuum-fried P. eryngii chips such as hardness, rehydration ratio, reducing sugar, protein and oil content were also measured. The results showed that the oil absorption of vacuum fried P. eryngii chips was affected by the porous structure. The oil content of vacuum fried P. eryngii chips was significantly and positively correlated with the pores with diameters above 50, 5–50, and 0.5–5 μm in the samples both before and after vacuum frying, while negatively correlated with the pores with diameters below 0.5 μm. Ultrasound pretreatment changed the microporous structure of P. eryngii chips, effectively hindering the oil absorption of samples. In particular, ultrasound assisted osmosis pretreatment induced the formation of more micropores. It was concluded that blanching + ultrasound assisted osmosis pretreatment is a promising method to reduce oil absorption and improve the quality of vacuum fried foods.

Effect of vacuum frying and atmospheric frying on the quality and protein oxidation of squid (Loligo chinensis)

Squid are commercial marine species that have high nutritional value. This study aimed to compare the influences of vacuum frying and atmospheric frying on the physicochemical properties and protein oxidation of three main parts (ring, tentacle, and fin) of the squid Loligo chinensis. The results showed that the vacuum-fried (VF) group had lower moisture and total fat contents and looser microstructures than the atmospheric-fried (AF) group. The amino acid contents and molecular weight revealed that the proteins were well preserved during vacuum frying. Carbonyl content in the VF ring, tentacle, and fin samples increased nearly 2.53-, 1.54-, and 2.56-fold, respectively, compared to that in the corresponding fresh group, but these increases were lower than those of the corresponding AF group. In addition, the secondary structures of proteins revealed a slight decrease in the α-helix and β-turn contents and a significant increase in the β-sheet content during vacuum frying. Therefore, vacuum frying can be used as an efficient processing method to conserve the high nutritive quality of the product. PRACTICAL APPLICATION: As a developing alternative technology to prepare healthier fried products, vacuum frying has been the focus of recent researches. Vacuum frying produced squid products that had lower TBARS values, carbonyl contents, and Schiff base substances compared to atmospheric frying. And the protein secondary structures of the vacuum-fried group retained better. The study proved that vacuum frying could be an effective method with the advantages of high protein stability and product quality.

Impacts of different blanching pretreatments on the quality of dried potato chips and fried potato crisps undergoing heat pump drying

Hot water blanching (WB) and steam blanching (SB) have been noted to improve the quality of potato chips. In this work, the possibility of steam blanching assisted with ultrasound treatment (SUB) to enhance the quality of dried potato chips and fried potato crisps was investigated. Compared to WB and SB groups, dried potato chips of SUB groups showed lower shrinkage ratio (78.46%), higher rehydration capability (3.93:1), and lower moisture content (0.08 g/g). Meanwhile, fried potato crisps of SUB groups displayed lower hardness (1965.70 g) and oil content (12.0%). The low reducing sugar content (0.42%) and free amino acid content (6.10 mg/g) in SUB dried potato slices could explain for the higher L * value, lower a * and ΔE values of SUB fried potato crisps. Additionally, sensory evaluation results confirmed above obtained consequences. Overall, SUB could improve the quality of fried potato crisps further in comparison with WB and SB.

Recent advances in physical fields-based frying techniques for enhanced efficiency and quality attributes

Frying is one of the most common units in food processing and catering worldwide, which involves simultaneous physicochemical and structural changes. However, the problems of traditional frying technology, such as low thermal utilization and poor processing efficiency, have been gradually exposed to industrial production. In this paper, strategies of applying physical fields, such as pressure field, electromagnetic field, and acoustic field in frying technology separately or synergistically with improved efficiency and quality attributes are reviewed. The role of physical fields in the frying process was discussed with modifications in heat and mass transfer and porous structures. The effects of physical fields and their processing parameters on moisture loss kinetics, oil uptake, texture, color, and nutrients retention of fried food are introduced, respectively. Recent advances in multi-physical field-based frying techniques were recommended with synergistic benefits. Furthermore, the trends and challenges that could further develop the multi-physical field-based frying techniques are proposed, showing further commercial prospects for the purpose. The application of physical fields has brought new inspiration to the exploitation of efficient and high-qualified frying technologies, while higher technical levels and economic costs need to be taken into consideration. HighlightsThe role of physical fields in pretreatments and frying process were reviewed.The mechanism of physics fields on frying efficiency and quality was summarized.The physicochemical and microstructure changes by physics fields were discussed.The synergy of physical fields in frying technology were outlined.The trends for further multi-physical field-based frying techniques were proposed.