# The Effect of Hybrid Drying Methods on the Quality of Dried Carrot
## 4 Discussion
Delicate conditions of the freeze-drying process affect low damage value in such samples. The high porosity of carrot dried in hybrid drying, freeze-drying and microwave-drying, was confirmed by structure; pores at the surface are regularly distributed, but areas with high, uniform density are visible, while in the central part numerous larger pores with irregular shapes were obtained. In addition, [PERSON] et al. [48] for hybrid drying of Lactobacillus paracasei F19 using microwave-freeze-drying observed that hybrid drying could produce a more open and porous structure, similar to freeze-dried samples, and this allows instant wetting and effective rehydration. The color parameter is defined as an indicator of the quality of fresh and processed raw materials. The attractive appearance and color of the product favorably affect the consumer's senses. The color of a given product depends on the amount and composition of dyes in the product. Carrots are evaluated and often chosen by consumers due to the content of a natural pigment, which is caroten, which determines the characteristic orange color of carrots [49; 50]. According to the literature, the \(\Delta\)E value is an important parameter showing the total color change in dried samples in comparison to raw material [51]. [PERSON] and [PERSON] [52] indicate that an inexperienced observer notices the difference in color when \(2<\Delta\)E \(<\) 3.5; when \(3.5<\Delta\)E \(<\) 5 a clear difference in color is noticed and when \(5<\Delta\)E the observer notices two different colors. In the range of \(0<\Delta\)E \(<\) 1, the observer does not notice the difference and in \(1<\Delta\)E \(<\) 2 only the experienced observer can notice the difference. All dried carrot samples obtained a high value of \(\Delta\)E coefficient above 15 units so the observer notices two different colors when comparing the dried sample with raw material. It was shown that microwave-dried carrots obtained the lowest value of the absolute difference in color. The lower the value of the \(\Delta\)E coefficient, the less the sample differs from the standard (raw carrot) [52]. The highest color changes compared to raw carrots were obtained for the freeze-dried sample. Hybrid drying was more favorable than freeze-drying taking into account color changes and microwave-drying with freeze-drying was the best. The drying process as a result of exposure to high temperatures on the material causes changes, e.g., in the structure of the tissue that causes contraction of the material, and a change in porosity. It is important for the color because the porous structure reflects radiation differently during color measurement [53]. Structure changes may be the reason for the highest color changes in freeze-dried carrot which was the most porous and with the highest lightness coefficient. A high value of color changes was obtained for convective-dried carrots, which confirmed [PERSON] et al. [54] for carrots and [PERSON] et al. [55] who showed that convective-drying of red bell pepper was a long process and caused a quality decrease. Structure changes were also observed, and color degradation during convective-drying probably was due to enzymatic and non-enzymatic browning reactions; while hybrid drying by combining convective-drying with infrared and microwave had a positive effect on the product quality and drying time. Shrinkage and deformations of samples were smaller, and color was protected. [PERSON] et al. [54] indicated also that for samples microwave dried, the color degradation may result from high temperatures occurring in the material due to microwave radiation. [PERSON] et al. [56] observed similar results for carrots dried in hot air with a microwave. Hybrid drying shows that microwave power should be applied according to the loss of moisture, which influences the microwave absorptivity and thus the drying efficiency, especially towards the end of drying.