Table 3.

Recent studies on the influence of high pressure processing on the drying performance of food materials

Food commodities	HPP conditions (pressure, time, and temperature)	Drying methods	Drying conditions (temperature/time/air velocity/RH)	Major findings	References
Beans	50 to 600 MPa for 1 min	Incubator	40 °C for 24 h	The effective moisture diffusivity was improved from 1.35 × 10–10 m2/s to 1.72 × 10–10 m2/s with an increase of isostatic pressure from 50 to 600 MPa The water diffusivity was enhanced by around 27% and increased drying rate for sample pretreated at 60 MPa/1 min	Belmiro et al. (2018)
Ginger	400 MPa for 10 min	Cabinet dryer	55 °C, 45%, 10 min, and 2 m/s	The effective moisture diffusivity was observed to be increased from 2.03 × 10–9 m2/s to 6.09 × 10–9 m2/s with an increase of isostatic pressure from 100 to 400 MPa for 10 min The oleoresin yield (28.29%) and 6-gingerol content (34.05%) were found to be higher than the control	George et al. (2018)
Aloe vera	300–500 MPa for 5–15 min	Dehumidified air drying	50–70 °C and 1–2 m/s	The effective moisture diffusivity of high pressure pre-treated samples was increased with the increase of treatment from 300 to 500 MPa The drying rate was improved with the rise of HPP treatment and temperature. The activation energy was found to be varied between 17.65 and 40.67 kJ/mol	Swami Hulle and Rao (2016)
Sweet potato, cocoyam, and Peruvian carrot	600 MPa for 5 and 30 min	Incubator chamber	50 °C, 0.127 m/s, and 23 h	The moisture diffusivity was enhanced by 35% at 600 MPa (5 min), 32% at 600 MPa (5 min), and 44% at 600 MPa (30 min) for sweet potato, cocoyam, and Peruvian carrot, respectively The drying rate was reported to be increased by around 30%, treated with 600 MPa for 10 min The permeability of cell structures was considerably improved due to high pressure processing, thereby enhancing mass transfer rate and subsequently reducing the total drying time	Oliveira et al. (2015)
Carrot and apple	100, 200, 250, and 300 MPa for 5, 15, 30, and 45 min	Hot-air tunnel dryer	27 °C, 45 °C, 65 °C, and 85 °C and 0.4 and 0.8 m/s	The application of high pressure processing above 100 MPa significantly reduced the drying time HPP treatments at 300 MPa and 20 °C or 200 MPa and 35 °C resulted in 10% shorter drying time as compared to the control The highest drying rate was obtained at 200 MPa, 15 min, and 35 °C for green beans and apples and 200 MPa, 15 min, and 20 °C for carrots drying at 65 °C and air velocity of 0.4 m/s	Yucel et al. (2010)
Peach	50–700 MPa for 5 and 10 min	Cabinet dryer	70 °C for 5 h	HPP treated peach slices increased the effective moisture diffusivity from 6.56 × 10−9 m2/s to 7.65 × 10−9 m2/s which improved with the increase of HPP treatment pressure and time High pressure processing improved the permeability, which resulted in drying rate improvement and minimized the drying time HPP treated samples showed less drying time (5 h) than control samples (7 h) Citric acid as a carrier fluid was observed to influence the drying rate	Kingsly et al. (2009b)
Potato	400 MPa for 15 min	Hot air convection drying	75 °C for 8–9 h	A higher drying rate was noted in high pressure pretreated samples during the initial phases of drying process The total color change for HPP pretreated samples was found to be lower as compared to thermally pretreated sample	Al-Khuseibi et al. (2005)