Rosemary Nutraceutical Industry Feasibility Study

 
 
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 Introduction | Rosemary cultivar evaluation | Effect of age of rooted stem cutting | Effect of plant population density

Introduction

Rosemary (Rosmarinus officinalis L.), a member of the Labiateae or mint family, is a slow growing, cold sensitive, woody perennial cultivated for the aromatic foliage. The crop is used primarily as a culinary herb with meats, vegetables and in soups. In traditional medicine, the plant is used as an astringent and diuretic, and to increase menstrual flow. Interest has been increased in using rosemary extracts as a source of phenolic compounds, which possess antioxidant properties that can be used in commercial food preparations. Norac Technologies, a division of Newlywed Foods in Edmonton, AB is currently extracts antioxidants from leaves of imported rosemary, using supercritical fluid extraction method. Preliminary studies conducted at the Crop Diversification Centre South (CDCS) indicated that rosemary plants produced under field conditions are superior in antioxidant contents than that of the imported rosemary. Norac Technologies is interested in using this high quality locally grown rosemary for their processing. This will require a detailed economic, risk, and logistic analysis of the cost and methods of production, screening of potential cultivars for foliage yield and antioxidant content.

A second part of the study was done in the greenhouses at CDCS to show technical feasibility and develop a technology to grow rosemary in Alberta as a greenhouse crop.

Objectives
This project examined:

  • the possibilities of growing rosemary as an annual crop under field conditions at CDCS, Brooks,
  • the impact of mild and killing frosts on plant growth and total phenolic content in rosemary,
  • the effect of nursery age of rooted stem cutting on plant growth and productivity of rosemary,
  • the effect of plant population density and soil nitrogen content on plant growth, productivity and total phenolic content of rosemary.


Field study 1. Rosemary cultivar evaluation for plant growth, foliage production and phenolic compound content

Materials and methods
This study was conducted using 8-week-old rooted stem cuttings of seven promising rosemary cultivars namely Apr, Blue Boy, Majorca, Santa Barbara, Severn Seas, Standard and Rex. Prior to the final land preparation, the test site was fertilized with 12:51:0 (N:P:K) fertilizer mixture at a rate of 42 kg ha-1. Stem cuttings were transplanted in the field on June 10, 2003, at a plant population density of 8 plants m-2. Each experimental plot (cultivar) consisted of 3 rows spaced 60 cm apart and each row contained 20 plants. Treatments (cultivars) were arranged in a randomized complete block design (RCBD) with 4 replicates. The crop was grown under irrigation and several rounds of hand weeding were carried out to keep the test plots free of weeds. Data collections included plant height, plant diameter, above ground dry weight, leaf and stem dry weights, and total phenolic activity (TPA = total phenolic content = Carnosic acid+ Carnosol + 12-Methoxy Carnosic acid content, expressed as a percentage of leaf dry weight) before and after mild killing frosts, using plants from middle rows of each plot. The phenolic compound extractions and quantification were performed at Norac Technologies, Edmonton, AB, Canada.

Results and discussion
Among tested rosemary cultivars, Arp and Standard were the tallest (38-41 cm), Severn Seas, Majorca and Rex were intermediate (27-32 cm) and Santa Barbara and Blue Boy were the shortest (8-11 cm). All cultivars, except Standard and Arp had lateral growth habit relative to vertical growth. Both Blue Boy and Santa Barbara produced lateral branches that are closer to the ground, which could hamper the mechanical harvest. Thus, these two cultivars may be not suitable for field production with mechanical harvest practice.



Rex, Majorca and Severn Seas produced significantly higher total above ground biomass, whereas Blue Boy produced significantly lower biomass, compared to Standard. In most cultivars, 2-fold increase in both total and leaf biomass production during the 7-week-period prior to killing frost. After mild frost all the cultivars, except Standard and Rex, has ceased the leaf biomass production. In rosemary, foliage portion contains over 85% the total antioxidant content (TPA = total phenolic activity). Thus, the leafiness (dry weight ratio between foliage portion and the total above ground portion) is more important than the total above ground biomass production. Results also suggest that leafiness of both rosemary cultivar Blue boy (88.6 %) and Santa Barbara (81.1 %) are significantly higher than the cultivar Standard (75.2 %) when those cultivars are 18 weeks old. The total phenolic compound contents were comparable (varied from 3.9% for Blue Boy to 4.8% for Standard) among cultivars when they were 13 weeks old. However, following a mild frost at 18 weeks of age and killing frost at 20 weeks of age the phenolic compound content slightly reduced in Standard, Rex, Apr and Severn Seas, but the antioxidant contents in Majorca, Santa Barbara and Blue Boy did not change, compared to that of 13-week-old plants. The total phenolic compound yield in foliage per plant was also calculated. Despite the fact that phenolic compound content slightly lowered as a result of aging, mild or killing frosts in aforementioned cultivars, Rex (2.09-2.28 g plant-1), Majorca (1.86-1.89 g plant-1), Standard (1.51-1.59 g plant-1) and Severn Seas (1.43-1.58 g plant-1) were superior in terms of phenolic compound yield under field production, due mainly to higher foliage production. These cultivars can also be harvested without having any adverse effect on the total phenolic compound production even after a killing frost.

Study 2: Effect of nursery age of rooted stem cutting on plant growth and foliage production in rosemary

Materials and methods
This study was conducted to evaluate the impact of age of rooted stem cutting on plant growth, productivity and total phenolic content of rosemary cultivar Majorca using 4-, 6- and 8-week-old rooted stem cuttings. The stem cuttings were transplanted at a spacing of 60 cm x 20 cm (8.3 plants m-2). Cultural practices were similar to that of the rosemary cultivar study. Data collections included plant height, plant diameter, total above ground biomass, and leaf and stem dry weights at 13 weeks after transplanting.

Results and discussion
Results indicated that age of rooted stem cuttings in nursery had no significant effect on plant height, but had a significant impact on plant diameter at 9 weeks after transplanting. Plants raised from 8-weeks old rooted stem cuttings had significantly wider diameters than those produced from 6-week and 8-week-old rooted stem cuttings. However, this treatment effect disappeared at 13 weeks after transplanting. The total above ground biomass production of plants raised from 8-week-old plants was significantly higher (13%) than that of the plants raised from the 4-week-old stem cuttings. However, age of rooted stem cuttings had no significant impact on leaf production. Plants raised from 8-week-old rooted stem cuttings produced significantly higher stem dry weight than that of those raised from 4-week-old rooted stem cuttings. This suggests that the increase in the above ground biomass of plants raised from 8-week-old stem cuttings was mainly due to enhanced stem production. Results also indicate that rosemary stems contain very lower amounts (< 15% of TPA) of phenolic compounds, compared to that of the foliage (Data not shown). Thus, the use of 8-week-old rooted stem cuttings as a planting material for field establishment appears to have no additional benefits in terms of leaf production, compared to the use of 4-week-old rooted stem cuttings. Results suggest that 4-week-old rooted stem cuttings can be used as a planting material for field production of rosemary.

Study 3. Effect of plant population density and soil nitrogen content on plant growth and total phenolic compound content of rosemary.

Materials and methods
This study was conducted to evaluate the effect of plant population density and soil nitrogen content on crop growth and total phenolic compound content of rosemary cultivar Majorca. The cultural practices were similar to the cultivar evaluation study. Basal fertilizer mixture (N: P: K = 12:51:0 at a rate of 42 kg ha-1) was applied prior to the final land preparation. Treatments included two plant population densities (60 cm x 20 cm = 8.3 plants m-2 and 30 cm x 20 cm = 16.7 plants m-2) and two nitrogen rates (50 and 100 N kg ha-1) arranged as factorial combinations. In addition, control plots applied with basal fertilizer mixture at a rate of 42 kg ha-1 and a plant population density of 8.3 plants m-2 were included. Each plot consisted of three rows and each row contained 15 plants. The treatments were arranged in a RCBD with 3 replications and data were collected from the middle row plants. Data collections included plant height and diameter, total biomass production, leaf and stem dry weights and TPA and total phenolic compound yield 13 weeks after transplanting.

Results and discussion
Results indicated that applied nitrogen and plant population density had no significant effect on plant height, diameter, total aboveground biomass leaf and stem production or total phenolic content. Among the treatments, the highest leaf production and phenolic compound yield were observed from the plants grown at a spacing of 30 cm x 20 cm at 50 N kg ha-1. Increasing N rates from 50 to 100 N kg ha-1 had no beneficial effect on either leaf production or phenolic compound production. In conclusion, our results suggest that rosemary crop can be successfully produced as an annual crop under moderate soil fertility and irrigated field conditions in southern Alberta.

 
 
 
 
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For more information about the content of this document, contact Manjula Bandara.
This document is maintained by Shelley Barkley.
This information published to the web on March 18, 2004.
Last Reviewed/Revised on March 17, 2010.