Shrinkage and rehydration characteristics of vacuum assisted microwave dried green bell pepper

Abstract

Green bell pepper was dried under vacuum assisted microwave (VAM) drying conditions. The effect of microwave power (100, 200, 300 W) and vacuum pressure (200, 400, 600 mmHg) were observed on shrinkage and rehydration characteristics of the sample. Shrinkage was modeled as a linear function of volume change of material and its moisture content. A model was proposed where apparent density could be evaluated as a function of product's moisture content. The sample volume in case of VAM drying shrunk by 59 to 78%, while in case of hot air drying, the shrinkage occurred up to 90%. At a given power level of 100 W, equilibrium rehydration values (Req) increased from 5.04 to 5.75 for samples dried at increasing vacuum pressure from 200 to 600 mmHg. Rehydration rate constant decreased correspondingly for samples dried at higher microwave power levels. Higher level of microwave power and vacuum pressure played significant (p < 0.01) role in producing more porous (lesser shrunken) product leading to higher diffusion (and thus better rehydrated product) of water through it. Diffusion coefficient in rehydration was calculated using Fick's second law. The values of “k” and “R2” varied from 1 × 10−3 to 6.4 × 10−3 and 0.986 to 0.999, respectively. Practical applications Shrinkage and rehydration characteristics of dried vegetables are of utmost importance when it comes to culinary preparations, premixes, convenient foods and retention of sensory qualities. The model proposed in the present study will be helpful in evaluating shrinkage as a function of apparent density and moisture content of dried green bell pepper. Several changes such as shape, size, structure, color, bulk density, porosity, and rehydration capacity are induced due to structural alteration in green bell pepper followed by drying. This information could help in safe commercial packaging of dried products. Further, dried green bell pepper must be rehydrated to be used in preparation of foods such as soups, pizzas, stews, casseroles, and many other recipes. Outcome of the current study can also be referred and implemented while accessing the rehydration characteristics of dried and shrunken vegetables.

Numerical Investigation of the Deformable Porous Media Treated by the Intermittent Microwave

“…Therefore, the simulation results of the radial and axial displacements matched well with the experimental data. Moreover, the deformation rates are also given in Figure 5, which indicates that the deformation rate reached the global maximum around 600 s due to the collapse of cell structure caused by moisture loss [56]. Moreover, the coefficients of determination and the root mean square errors of the two models were R 2 = 0.437 and R 2 = 0.345, and RMSE = 13.5 • C and RMSE = 15.4 • C, respectively.…”

Effect of Different Drying Systems on Drying Performance of Maraş Green Pepper (C.annum)

“…The appropriate drying method, especially for sensitive biological products such as green pepper, is important for both the quality of the dried product and the expenses of the process (Mahanti et al, 2021). Vacuum-assisted microwave drying (Kumar et al, 2019;Kumar and Shrivastava, 2017), heat pump-assisted fluidized bed drying (Jafari et al, 2016), IR-assisted spouted bed dryer (Moradi et al, 2020) and osmotic drying (Odewole et al, 2016) are recent studies on green pepper. No study was found on Maraş green pepper in the literature review.…”

Convective drying of sweet pepper (Capsicum annuum L. 'Tres Cantos') and yellow onion (Allium cepa L. 'Yellow Granex F1')

“…Correlation constants and ANOVA of the linear model representing the volumetric shrinkage at various drying conditions(Mazza and Lemaguer, 1980;Kumar et al, 2019) …”