Ultrasonic Pretreatment-Assisted Electrohydrodynamic Drying of Potato Slices

To investigate the drying characteristics and mechanism during electrohydrodynamic (EHD) drying with ultrasonic pretreatment, the ultrasonic pretreatment-assisted EHD drying method at different power values was used to carry out the drying experiment of potatoes. To carry out this study, potato slices were pretreated with different ultrasonic power values (150, 180, 210, 240, and 270 W) or without ultrasound for 30 min at 30°C. The corresponding voltage was 18 kV during EHD drying. The moisture ratio, drying rate, color, shrinkage, and rehydration rate of potatoes were determined. The microstructure of potatoes was analyzed using infrared spectroscopy and scanning electron microscopy. Eight mathematical models were used to fit the drying of potatoes. Results showed that, compared with the control group, the ultrasonic pretreatment combined with the EHD drying group had improved the drying rate of potato slices, which was different at varying ultrasonic power values. Ultrasonic pretreatment had a remarkable effect on the color of the potato but had little effect on the shrinkage rate. The maximum rehydration rate is 5.7704 at 180 W. The minimum and maximum values of effective moisture diffusivity (Deff) were 3.4070 × 10−7 m2/s and 4.1160 × 10−7 m2/s, respectively. The effect of ultrasonic power pretreatment on the microstructure of potato in the EHD drying process was significant ( p > 0.05 ). According to the statistical parameter evaluation, eight mathematical models could satisfactorily describe drying curves of potato slices dried under EHD with ultrasonic pretreatment, and the logarithmic model was best suited. This work provides a theoretical basis and practical guidance to further understand the parameter characteristics and mechanism of ultrasonic pretreatment combined with the EHD drying technology.

Effect of soaking conditions on properties of flour from sweet potato slices

Native flour of sweet potato has limited industrial applications. This study investigated effect of soaking sweet potato root in hot water and citric acid concentrations on flour properties. Sweet potato root was soaked at temperatures of 50oC, 60oC and 70oC for 2 h; citric acid concentrations of 1%, 3% and 5% for 1 h, and combination of best samples in each of the first two modification treatments in 50:50 proportions. Treated root was processed into flour using standard procedures. Proximate, functional and pasting properties of the flours were determined using standard methods. The flour was used as major ingredient in production of baked snacks. Treatments had significant effect on proximate, functional and pasting properties of the flour. Moisture content ranged from 6.5 to 9.7%, protein content 1.6 to 3.0%, ash content 0.1 to 3.15%, fiber content 3.6 to 4.2%, and carbohydrate content 82.1 to 84.7%. Water and oil absorption capacities ranged from 2.2 to 3.0 ml/g and 0.8 g/ml to 1.8 g/ml respectively, swelling power (4.32 to 9.23 g/g) and bulk density (0.77 to 0.95 g/ml). Snack produced with flour gotten from 60oC soaked root for 2 h was best in sensory ratings.

Influence of Drying Methods and Vacuum Impregnation on Selected Quality Factors of Dried Sweet Potato

A comparative study was conducted on the effect of vacuum impregnation and drying methods on the production of dried sweet potatoes with high bioactivity. The present study determined the quality and physicochemical properties of dried sweet potato depending on the used impregnating solutions. Sweet potatoes were pretreated in freshly squeezed onion (O) and kale (K) juice, onion and kale (OK) mixture (1:1), and sodium chloride solution. Vacuum impregnation (VI) was carried out under reduced pressure (6 kPa) for 2 min, after which the impregnating solution was dispensed and maintained under vacuum for 4 min. Sweet potato slices were dried using vacuum drying (VD) and freeze drying (FD) methods. Higher content of polyphenols, carotenoids, and chlorophyll, as well as increased antioxidant capacity and higher VOC profile, were recorded for the dried products obtained using the sublimation method. The use of vacuum impregnation reduced the hardness of the products and other textural characteristics, such as cohesiveness, springiness, and gumminess. Furthermore, we found that vacuum impregnation pretreatment was a beneficial method for improving the characteristics of dried vegetables. The highest content of phenolics, carotenoids, and chlorophylls in dried sweet potatoes were recorded when samples were impregnated with onion and kale juice. For the fresh sweet potato, the highest contribution in VOC composition had phenylacetaldehyde (44.90%), (E)-2-octen-1-al (9.43%), and benzaldehyde (8.18%), respectively. The interesting content of VOC profile compounds in dried sweet potatoes was recorded when samples were impregnated with kale juice.

Effect of UV-C Irradiation, Storage and Subsequent Cooking on Chemical Constituents of Fresh-Cut Potatoes

UV-C irradiation successfully reduces the growth of microorganisms, but it can also affect the content of phenolics and sugars of fresh-cut potatoes (FCP). This could consequently alter antioxidant capacity of FCP or its potential for acrylamide formation. Therefore, this paper investigates the influence of UV-C irradiation on the content of phenolics [chlorogenic acid (CA)] and individual sugars during storage of FCP as well as after cooking. Acrylamide was also monitored in FCP after frying. Potato slices pre-treated with sodium ascorbate solution and vacuum-packaged were UV-C irradiated for 0, 3, 5, and 10 min in order to obtain irradiation doses of 0, 1.62, 2.70, and 5.40 kJ m−2, respectively, stored for 23 days (+6 °C), and subsequently boiled and fried. As the applied dose and storage duration increased, the CA content in raw FCP decreased (it retained for 75.53–88.34%), while the content of sugars as well as acrylamide in fried FCP increased. Although the increase was the most noticeable at the applied dose of 2.70 kJ m−2, the acrylamide content was always below proposed limit. Boiling and frying reduced the content of CA and sugars. In spite of certain alterations, applied doses of irradiation can ensure acceptable product in regard to phenolics and sugars, and acrylamide content particularly.

Reducing the Acrylamide Concentration in the Potato Chips Product by Using Sea Salt, Green Pepper and Thyme

The study was conducted to show the effect of adding different percentages of Sea Salt solution and aqueous extracts of green pepper and thyme individually or in combination, it reduces the Acrylamide content in the potato chips product when exposed to high temperatures during processing, potato slices were treated by soaking before frying with C1 (0.1, 0.2, 0.3) % Sea Salt solution and the aqueous extract of Green Pepper C2 and thyme C3 in proportions (1, 2,3)% and a mixture of the three additives C4, the treatment C was left to be the control, High performance liquid chromatography technology (HPLC) was used to estimate the concentration of acrylamide in the treatments, sensory evaluation to the parameters of taste, color, odor, texture and general acceptance was conducted, the results showed a clear decrease in the acrylamide concentration in the potato chips treatments by increasing the concentration of the additives, C4 treatment with the synergistic action of Sea Salt, thyme and Green Pepper outperformed all other treatments in decreasing the acrylamide concentration, The results were descending C4 > C2- 3% C3- 3% > C1- 3% amounting to 0.013, 0.024, 0.034 and 0.084, respectively, compared to the control treatment 0.522, the results of sensory evaluation recorded the highest degree of receptivity to the treatments by increasing the percentage of additives, and the results were descending C4 > C3> C2 compared to the control treatment.