Stinging Nettles as Potential Food Additive: Effect of Drying Processes on Quality Characteristics of Leaf Powders

Abstract

Stinging nettle (Urtica dioica L.) is a ubiquitous, multi-utility, and under-utilized crop with potential health benefits owing to its nutritional and bioactive components. The objective of the work is to produce powders by drying wild stinging nettle leaves as a storable, low-cost functional additive to be used in bakery and ready-to-cook products. Convective drying (CD) and freeze-drying (FD) were applied on unblanched (U) or blanched (B) leaves, which were then milled to nettle powders (NPs). The obtained NPs were evaluated for selected physicochemical (moisture, color), techno-functional (flow indices, hygroscopicity), and phytochemical (pigments, phenols) characteristics as well as mineral contents. Blanching improved mass transfer and reduced the oxidative degradation of pigments during drying, but it caused a loss of total phenols content, antioxidant activity, and potassium content. As for the drying method, CD resulted in better flow properties (i.e., Carr Index and Hausner Ratio), while FD retained better the color, pigments, magnesium content, phenolic, and antioxidant parameters. Overall, the evaluated processing methods resulted in different technological properties that can allow for better evaluation of NPs as a food additive or ingredient. Among the NPs, blanched and freeze-dried powders despite showing inferior technological properties can be recommended as more suitable ingredients targeted f or food enrichment owing to better retention of bio-active components.

Aloe vera Gel Drying by Refractance Window®: Drying Kinetics and High-Quality Retention

“…Over 85% of industrial food dryers are convective, with mostly hot air as the media for heat transfer; often resulting in significant levels of changes in product quality from the initial fresh-like form [ 17 ]. Along with food quality retention, energy efficiency is equally important in the drying process, which is why both aspects are the subject of intensive research and development on food science [ 18 , 19 , 20 , 21 ]. Among the technologies currently deployed for the drying of valuable products, freeze-drying is very expensive, and despite the high-quality of its products, its use is limited to high-value products [ 15 , 18 , 22 ].…”

“…Along with food quality retention, energy efficiency is equally important in the drying process, which is why both aspects are the subject of intensive research and development on food science [ 18 , 19 , 20 , 21 ]. Among the technologies currently deployed for the drying of valuable products, freeze-drying is very expensive, and despite the high-quality of its products, its use is limited to high-value products [ 15 , 18 , 22 ]. Thus, there is a strong need for developing alternative drying technologies considering operational capacity, process control, time requirements, cost economics, product quality, safety, and environmental aspects.…”

Environmental Impact Assessment of Organic Wheat Cracker Value Chains with and without Nettle Powder as a Natural Additive: A Case of Sweden

“…Nettle is one of plants that can be used as natural additives in food processing, e.g., in bakery. It has nutritional and bioactive components with potential health benefits [30]. It can be used as a nutritional ingredient in bakery, e.g., in baking wheat crackers.…”

Ultraviolet-c Radiation Induced Changes on Bioactive Compounds Content, Antioxidant Capacity and Microbial Quality of Minimally Processed Molokhia (Corchorus Olitorius L.) Leaves

“…Antioxidant capacity (AC) of eggplant samples extracts and standards (Trolox equivalent, TE) was determined by Trolox equivalent Antioxidant capacity (TEAC) assay according to the procedures mentioned by Nallan, et al [32] using the specific assay kit (Cell Biolabs, Inc., San Diego, CA, USA).…”