Protein Hydrolysates Supplement in the Nutrient Solution of Soilless Grown Fresh Peppermint and Spearmint as a Tool for Improving Product Quality

Danai-Christina Aktsoglou,Eirini Sarrou,Paschalina Chatzopoulou,Pavlos Tsouvaltzis,Stefan Martens,Anastasios S. Siomos,Dimitrios S. Kasampalis

doi:10.3390/agronomy11020317

Abstract

The present study investigated the potential of fresh peppermint (Mentha × piperita L.) and spearmint (Menthaspicata L.) production on a floating raft system combined with a commercial protein hydrolysate supplement (Amino16®) in a nutrient solution aiming to improve plant product quality. Three levels of the protein hydrolysate solution (0, 0.25 and 0.50%) were added in the nutrient solution, and the plants were harvested after twenty-four days. Plant growth characteristics were recorded, and nutritional, essential oil and polyphenolic composition were determined in fresh tissue. The addition of protein hydrolysates did not affect the fresh or dry weight but reduced plant height. Nitrate content significantly decreased, while total chlorophyll and essential oil content increased in both species. Moreover, the protein hydrolysate solution further increased total antioxidant capacity, total soluble phenol and carotenoid contents in spearmint plants, while it did not affect the essential oil and polyphenolic composition in both species. In conclusion, protein hydrolysates solution may be added in the nutrient solution, to improve the quality of peppermint and spearmint grown in a floating system, without adverse effects on crop yield or the essential oil and polyphenolic profile.

Highlights

Peppermint (Mentha × piperita L.) and spearmint (Mentha spicata L.) are aromatic perennial herbs that belong to the Lamiaceae family, and both contain essential oil with high economic value [1]
While over the majority of the growing period, the electrical conductivity (EC) remained constant, twenty days beyond the start date, a rapid increase in the EC of the control nutrient solutions (NSs) was observed, reaching 6.2 dS/m, while a slighter increase was found in the 0.25% Protein hydrolysates (PHs) NS solution (5.1 dS/m), and no change was exhibited in the high
The pH of the control NS at the time of preparation was 7.2, and the addition of the PHs solution resulted in a significant decrease to 5.5 and 4.1 in the low and high dosage, respectively

Summary

Introduction

Peppermint (Mentha × piperita L.) and spearmint (Mentha spicata L.) are aromatic perennial herbs that belong to the Lamiaceae family, and both contain essential oil with high economic value [1]. The chemical composition of spearmint essential oil may vary widely among the natural populations, resulting in nine chemotypes, depending on the main essential oil components, with carvone and limonene type being the dominant ones [3]. Both plants produce stolons that grow aboveground or underground and are grown for fresh or dry use during cooking or as herbal tea, or even for their essential oils, used in the food, pharmaceutical and perfumery industries [1,2,3]. The main antioxidant components of peppermint and spearmint are the essential oil, polyphenols, vitamins and carotenoids [2,4]

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