The Effect of Infrared Drying on Color, Projected Area, Drying Time, and Total Phenolic Content of Rose (Rose electron) Petals

Revealing the mechanism of post-harvest processing on rose quality based on dynamic changes in water content, enzyme activity, volatile and non-volatile metabolites

Existing studies on post-harvest processing of edible roses have mainly focused on processing techniques and physicochemical properties of the final dried products, with limited studies on how changes in metabolites during processing affect the quality of these products. This study investigated changes in water content and status, enzyme activity, phenolic compounds, and volatile and non-volatile compounds during processing and revealed the mechanisms by which post-harvest processing (drying without blanching (WBD) and drying with blanching (BD)) affects the quality of dried roses by establishing their correlations. Results showed that the blanching reduced the relative content of free water and water activity, thus reducing the subsequent drying time and enzyme activity. The BD method caused higher levels of phenolic compounds than the WBD method in terms of gallic acid, ellagic acid, epicatechin, and quercetin. The OPLS-DA analysis identified 6 differential volatiles out of 72 detected volatiles, contributing to the unique aroma of dried roses by activating olfactory receptors through hydrogen bonding and hydrophobic interactions. 58 differential metabolites were screened from 964 non-volatile metabolites. KEGG pathway analysis revealed that the changes in volatile and non-volatile metabolites induced by different processing methods were due to the effect of blanching on glutathione and fatty acid metabolism. These findings provide a comprehensive understanding of how post-harvest processing affects the quality of dried roses.

Production and evaluation of total phenolics, antioxidant activity, viscosity, color, and sensory attributes of quince tea infusion: Effects of drying method, sonication, and brewing process

This study aimed to examine the influence of drying approaches (convective and infrared (IR)), sonication, and brewing time on the total phenolic content (TPC), antioxidant activity (AA), viscosity, color indexes, and sensory attributes of quince tea infusion (QTI). The AA and TPC in the QTI dried in the IR dryer were higher than in the convective dryer. The TPC and AA of QTI prepared by convective and IR dryers increased when the ultrasound treatment and brewing time were increased. In terms of viscosity and Brix, there was no differences between the QTIs and the average viscosity and density of the samples were 1.79 ± 0.28 mPa.s and 3.18 ± 0.07°Brix, respectively. The QTI prepared by the IR has a reddish-brown hue (higher a* value), but the samples prepared with the convective dryer were yellow (higher b* value). The sensory attributes scores of QTI prepared by IR were higher than those of convection-dried samples. In general, the use of an IR dryer for drying grated quince, ultrasound treatment for 8 min, and brewing time for 30 min is a promising condition for the production of QTI with higher TPC and AA, and with appropriate color and sensorial acceptance.

Impact of Drying Conditions on Antioxidant Activity of Red Clover (Trifolium pratense), Sweet Violet (Viola odorata) and Elderberry Flowers (Sambucus nigra)

Flowers of red clover (Trifolium pratense), sweet violet (Viola odorata) and elderflowers (Sambucus nigra) were dried by means of air drying at 30 °C and 50 °C and by freeze drying. The content of polyphenols was determined using the Folin–Ciocalteu reagent, while anthocyanins were quantified by the pH differential method. Antioxidant activities of aqueous and ethanolic extracts of the dried flowers were measured by the DPPH and ABTS assays, as well as FRAP and reducing power methods. The highest amount of polyphenols was determined in the ethanolic extracts of fresh red clover flowers (854.76 mg/100 g), while the highest concentration of anthocyanins was determined in the aqueous extracts of fresh sweet violet flowers (99.41 mg/100 g). The results showed that, in general, the extracts of red clover flower were characterized by the highest antioxidant activity, while the sweet violet extracts had the poorest antioxidant properties, although these values fluctuated depending on the method used. There was strong correlation between antioxidant activity and TPC (r = 0.9196, FRAP method). In most cases, freeze drying was found to be the best conservation method, retaining well the antioxidant properties of the tested flowers and the compounds determining these properties.

Short- and Medium-Wave Infrared Drying of Cantaloupe (Cucumis melon L.) Slices: Drying Kinetics and Process Parameter Optimization

The main objective of the present work was to study the drying kinetics and obtain the optimum process parameters of cantaloupe slices using short-and medium-wave infrared radiation (SMIR) drying technology. The effect of three independent variables of infrared radiation temperature (55–65 °C), slice thickness (5–9 mm) and radiation distance (80–160 mm) on the L value, color difference (∆E), hardness and vitamin C content were investigated by using the Response Surface Methodology (RSM). The results showed that the Page model can adequately predict the moisture content between 55 and 65 °C (R2 > 0.99). The effective moisture diffusivity (Deff) varied from 5.26 × 10−10 to 2.09 × 10−9 m2/s and the activation energy (Ea) of the SMIR drying was 31.84 kJ/mol. Infrared radiation temperature and slice thickness exerted extremely significant effects on L value and color difference (ΔE) (p < 0.01), with higher infrared radiation temperature and thin slice thickness leading to a decrease in the L value and an increase in ΔE. Hardness and vitamin C content were significantly affected by infrared radiation temperature, slice thickness and radiation distance, of which the slice thickness was the most distinct factor affecting the hardness value. Higher infrared radiation temperature and larger slice thickness and radiation distance resulted in higher vitamin C degradation. For the given constraints (maximized vitamin C content and L value, minimized ΔE and hardness value), the optimum drying parameters were infrared radiation temperature 58.2 °C, slice thickness 6 mm and radiation distance 90 mm. Under the optimum drying combination conditions, the experimental values were 65.58 (L value), 8.57 (∆E), 10.49 N (hardness) and 106.58 mg/100 g (vitamin C content), respectively. This study is beneficial to the development of the cantaloupe food processing industry and provides more insights for the application of SMIR drying technology to improve the drying rate and product quality of cantaloupe.

Infrared Drying Trends Applied to Fruit

Aims: This article seeks to identify the main products to which drying is applied, mainly by infrared, as well as the mathematical models used to evaluate a product.

Background: The drying of agro-industrial products is a very important unitary operation to avoid post-harvest losses.

Objective: This article looks to respond to the following questions: Which raw materials are subjected to far-infrared drying? What are the mathematical models used in the application of far-infrared?

Method: To identify the most focused articles on the topic, we worked with the search equation “TITLE-ABS-KEY (‘infrared drying’) AND fruits AND [LIMIT-TO (SUBJAREA, ‘AGRI’) OR LIMIT-TO (SUBJAREA, ‘ENGI’)],” which was run in the Scopus database for scientific articles.

Result: After knowing the different technologies, more than 23 applications in agro-industrial products were identified. In these applications, it is observed how quality is one of the most important factors in the preservation of dehydrated products; far-infrared drying helps retain sensory quality in products such as sweet potatoes, grapes, Cordyceps militaris, and mangoes.

Conclusion: A common factor that could be found from the articles and patents was the application of this infrared drying technique in fruits and vegetables with high water content, such as kiwi, chives, and mushroom varieties. These articles and patents based their studies on optimizing the technique by varying drying times, temperatures, and pressures, even sometimes combining different drying techniques—all to preserve the organoleptic characteristics of the product, avoiding damage to thermolabile compounds and obtaining a dry food of very good quality, performance, and characteristics.

Impact of production and drying methods on the volatile and phenolic characteristics of fresh and powdered sweet red peppers

Aroma, phenolic compounds and sensory properties of fresh and powdered organic and conventional sweet red peppers dried by three methods (hot air, intermittent microwave and infrared) were studied. The number of aroma compounds was higher in both fresh and powdered organic pepper samples; however, the total amount was higher in conventional samples. In both organic and conventional samples, alcohols were the dominant aroma group. (E)-β-ionone and β-ocimene, which are important compounds in peppers, were determined only in organic peppers. Among the drying methods, intermittent microwave drying was more effective in creating new aroma compounds. The liquid chromatography, coupled with tandem mass spectrometry (LC-MS/MS) revealed that luteolin derivative compounds comprised an average of 70% of the phenolics. Higher amount of phenolic were determined in organic samples. Infrared drying was more effective in retaining of phenolics than the other two methods. Sensory analysis revealed that hot air-dried samples were least preferred.