Diurnal effects on spearmint oil yields and composition

Authors: BUFALO, JENNIFER - Universidade Estadual Paulista (UNESP); ZHELJAZKOV, VALTCHO - University Of Wyoming; Cantrell, Charles; ASTATKIE, TESS - Dalhousie University; CIAMPA, LYN - University Of Wyoming; JELIAZKOVA, EKATERINA - University Of Wyoming

Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2014
Publication Date: 1/7/2015
Publication URL: http://handle.nal.usda.gov/10113/62285
Citation: Bufalo, J., Zheljazkov, V.D., Cantrell, C.L., Astatkie, T., Ciampa, L., Jeliazkova, E. 2015. Diurnal effects on spearmint oil yields and composition. Scientia Horticulturae. 182:73-76.

Interpretive Summary: Mentha remains an economically important genus of the Lamiaceae family with about 19 species and 13 natural hybrids. One the most common species for cultivation is Mentha spicata L.. This species is cultivated commercially for use in teas and for essential oil production which has economic importance in perfumery, confectionary and pharmaceutical preparations and specialty chemical production. Commonly called spearmint, the variety ‘Native’ is widely grown in the United States and other countries. The two major constituents of spearmint oil are carvone and limonene. It is not known if the essential oil yield (content) and composition of spearmint oil are affected by diurnal variation, and when it would be the best time for harvesting flowering spearmints within a 24 h period. Therefore, the objective of this study was to evaluate the effect of diurnal variation on yield and composition of spearmint ‘Native’ essential oil for the environmental conditions of Northern Wyoming, at elevation 1170 m above the sea level. The experiment was conducted on a 3-year old well established spearmint plantation. The harvest times were every 2 h within a 24-h period: 7:00AM, 9:00 AM, 11:00AM, 1:00 PM, 3:00 PM, 5:00 PM, 7:00 PM, 9:00 PM, 11:00 PM, 1:00 AM, 3:00 AM, and 5:00 AM. Essential oil yield varied from 0.96 to 1.47 g of oil per 100 g of dry herbage; the maximum oil yield was obtained at 9:00 AM and the minimum at 7:00 PM. For best essential oil yields, flowering spearmint should be harvested at around 9:00 AM. However, to obtain oil with high carvone concentration, spearmint should be harvested at 9:00 PM. Harvests at 1:00 PM would result in spearmint oil with low concentrations of both carvone and limonene, and hence, should be avoided.

Technical Abstract: ‘Native’ spearmint (Mentha spicata L.) is one of the two spearmint species grown commercially in the United States and other countries for essential oil production. The two major constituents of spearmint oil are carvone and limonene. It is not known if the essential oil yield (content) and composition of spearmint oil are affected by diurnal variation, and when it would be the best time for harvesting flowering spearmints within a 24 h period. Therefore, the objective of this study was to evaluate the effect of diurnal variation on yield and composition of spearmint ‘Native’ essential oil for the environmental conditions of Northern Wyoming, at elevation 1170 m above the sea level. The experiment was conducted on a 3-yearold well established spearmint plantation. The harvest times were every 2 h within a 24-h period: 7:00AM, 9:00 AM, 11:00AM, 1:00 PM, 3:00 PM, 5:00 PM, 7:00 PM, 9:00 PM, 11:00 PM, 1:00 AM, 3:00 AM, and 5:00 AM. Essential oil yield varied from 0.96 to 1.47 g of oil per 100 g of dry herbage; the maximum oil yield was obtained at 9:00 AM and the minimum at 7:00 PM. The concentration of carvone in the oil varied from 44.1% (at 1:00 PM) to 66.4% (at 9:00 PM) of the total oil. However, the yield of carvone (a function of oil yield and carvone concentration in the oil) was the highest at 3:00 AM and the lowest at 1:00 PM. The concentration of limonene (10.7–15.8% of the oil) was the highest at 7:00 PM and the lowest at 1:00 PM, whereas the yield of limonene was the highest at 9:00 PM. For best essential oil yields, flowering spearmint should be harvested at around 9:00 AM. However, to obtain oil with high carvone concentration, spearmint should be harvested at 9:00 PM. Harvests at 1:00 PM would result in spearmint oil with low concentrations of both carvone and limonene, and hence, should be avoided.