Effect of Temperature on the Drying Behavior and Quality of Citrus Peels

Abstract

The effects of the drying temperature and the residual moisture content on the drying behavior, energy consumption and quality of dried citrus peels (CPs), which are value-added food ingredients, were studied. The CP samples were dried in a laboratory-scale hot-air dryer at air temperatures from 40 to 70 °C under a constant air velocity of 1 m/s until the desired moisture content for safe storage was reached or until the final moisture level was achieved for the specific drying conditions. Cakes prepared from blends containing different proportions (0 %, 10 %, 15 % and 20 %) of dried CPs were also evaluated for chemical composition and sensory attributes. The optimal drying temperatures were 50–60 °C, and the optimal moisture content was 10±0.2 % w.b.; these conditions reduced the drying time and energy consumption and maximized the product quality. In contrast, over-drying CPs with the higher temperatures and to a final moisture level of 5.4±0.2 % sharply increased the loss of vitamin C, carotenoids as antioxidants and essential oils. Incorporation of 15 % dried orange and mandarin peels in cake formulas increased the dietary fiber by 33.5 % and 29.6 %, the crude fat by 2.9 % and 4.6 % and the ash by 30.6 % and 29.0 %, respectively, whereas the protein and total carbohydrate content decreased slightly. Highly acceptable nutritious cakes could be obtained by incorporating 15 % orange or mandarin peel dried to 10 % w.b. moisture content into the formulation.

Effect of hot air drying on the polyphenol profile of Hongjv ( Citrus reticulata Blanco, CV. Hongjv) peel: A multivariate analysis

“…It took 180 min, 240 min, 300 min, and 360 min to achieve MC s of 3.64%, 7.18%, 7.34%, and 7.06%, respectively, at HAD temperatures of 50°C, 60°C, 70°C, and 80°C, respectively, from the HP’s initial MC of 74.6%. Previous research has reported that oven drying of mandarin and orange peels, required 360–540 min and 300–420 min, respectively, (Marey & Shoughy, 2016). Thus, the high drying temperature in this study increased the drying rate, thereby shortening the length of time required to dry the HP.…”

“…As shown in Figure 1b, the curve of the drying rate of HP during the initial drying stage clearly rose and, subsequently, dropped as the HAD time increased. However, the abovementioned study of the oven drying of citrus peel reported only the phase in which the drying rate fell (Marey & Shoughy, 2016). This difference in the drying rate curve indicates a different mechanism of water transfer.…”

“…Citrus is among the world's most important fruit crops, with average annual production of approximately 116 million tons (Marey & Shoughy, 2016). Hongjv ( Citrus reticulata Blanco, CV.…”

Is air-drying of plant-based food at low temperature really favorable? A meta-analytical approach to ascorbic acid, total phenolic, and total flavonoid contents

“…Ascorbic acid can be easily degraded depending on various factors like temperature, drying time, moisture content, air velocity, sample geometry, the presence of enzyme, oxygen and metallic catalysts. (5) Considering the drying temperatures in the range from 40°C to 80°C, the higher the drying temperature, the greater ascorbic acid losses have been observed for many plant-based products (8,15,19,36,43); however, AA content may also increase when dried at 50°C as was observed in salak fruit (9), tomato slices (40) and pears. (37) Gamboa-Santos et al 7found similar amount of ascorbic acid in strawberries after drying at 40°C and 50°C for 7 h. The initial moisture content of the products plays a key role during the thermal degradation of ascorbic acid.…”

Effect of Drying Temperature on Physiochemical Properties of Powder from Blanched and Unblanched Lemon Peel and Sensory Quality Evaluation of the Powder Fortified Biscuits

“…To inactivate enzymatic reactions during processing, blanching is generally carried out before drying [14]. Marey and Shoughy [15] reported that quick drying is very essential to reduce the moisture content to a safe level previous to further processing because of the high moisture content of the citrus residuals after processing.…”