The
              Report

No. 69: Storing and handling 
culinary herbs


The full report
This is a summary of a full report published by RIRDC titled ‘Storage of Culinary Herbs ’ (Pub no 99/142,DAV-103A) by Mr Bruce Tomkins and Anita Chennell, Institute for Horticultural Development, Victoria. Phone: (03) 9210 9222, fax: (03) 9800 3521. The report is available in hardcopy or downloadable from this site (under New Plant Products.

Postharvest handling and packaging methods developed from research funded by the Rural Industries Research and Development Corporation (RIRDC)has potential to improve local and export markets for Australian culinary herbs.

Market development and expansion has so far been restricted by the extreme perishability of many fresh herbs and limited knowledge of best handling and storage practices.

Following up an earlier RIRDC-funded project on Australian culinary herbs, researchers Anita Chennell,Bruce Tomkins and Peter Franz of Agriculture Victoria ’s Institute for Horticultural Development at Knoxfield,undertook the new project to provide guidance for the Australian herb industry.

The work identified and assessed the postharvest physiology,handling and storage requirements of eight major culinary herbs.

The Study

The project ’s objective involved minimising quality loss and adding value to culinary herbs and fresh herb products by developing optimum postharvest protocols and new modified atmosphere packaging systems.

The specific aims were to determine or identify:
 

  • air respiration rates of major culinary herbs at different storage temperatures;
  • maximum storage life and major limits to shelf life of major culinary herbs at different storage temperatures;
  • the best controlled atmosphere at 0 °C;
  • the best modified atmosphere package and temperature to achieve maximum storage life;and
  • optimum postharvest handling protocols.


    • Freshly cut culinary herbs – chervil (Anthriscus cesefolium ), coriander (Coriandum sativum ), continental parsley (Petroselinum crispum var. neopolitarum ), mibuna, mizuna, rocket (Eruca vesicaria ) and supreme cress (Nasturtium officinale ) were obtained on different occasions from a property in Pearcedale,Victoria.

    The produce had been hand harvested,washed in sanitised water,lightly dried and stored at 0 °C, 24 hours prior to packing.

    Sweet basil (Ocimum basilium) was obtained from Mareeba in Queensland. It was picked a few days before packing but not washed.

    All the produce was collected and transported to the Institute for Horticultural Development, in Knoxfield Victoria,under an insulated wrap, or in the case of basil,in lidded,expanded polystyrene boxes under refrigeration.

    With the exception of the controlled atmosphere storage trial,all trials were a randomised complete block design with six to eight replicates per treatment.

    The series of trials started by examining respiration rates to help determine suitable temperatures and atmospheres for controlled storage and for subsequent design of modified atmosphere packaging.

    The second trial was a high humidity air storage trial aimed at finding the maximum storage life of each herb using sophisticated packaging or controlled atmosphere storage and modified atmosphere-packaging.

    A third trial involved controlled atmosphere storage to determine the optimum storage atmosphere that would then be used in the subsequent design of modified atmosphere packaging.

    Two more trials using modified atmosphere packaging (MAP)were undertaken.The first tested the storage potential of chervil,coriander, mizuna and supreme cress in low-density polyethylene (LDPE)bags at 4 °C and 8°C.

    The second trial involved all eight of the culinary herbs stored in biaxially orientated polypropylene (BOPP)bags of varying thickness (30,50 and 70-micron)at temperatures of 4 °C and 8 °C.

    Three smaller trials were carried out over the duration of the RIRDC project.

    These separately evaluated the effect of field spray regimes and commercially available packaging on product quality during storage.

    Herbs involved were mibuna,mizuna,a mesclun salad herb mix,and a series of commercially available individually packed herb products.

    The Results

    In the respiration rate trial,the culinary herbs of coriander,continental parsley,mibuna,mizuna, rocket and supreme cress were stored in air at 0 °C,3 °C and 8 °C and basil at 8 °C,10 °C,12 °C and 15 °C.

    Results showed all herbs respired less at the lower temperatures of 0 °C and 3 °C with basil respiring moderately less at 8 °C.

    The high humidity air storage trial showed quality loss of non-chill sensitive herbs was minimised and storage life was prolonged below 4 °C.The rate of product deterioration,expressed as leaf yellowing and soft rots,increased substantially when stored at 8 °C.In the case of basil,chilling injury occurred when stored below 10 °C – this was expressed as leaf blackening..

    The optimum storage temperature for basil appears to be 10 °C to 12 °C.

    In the controlled atmosphere storage trial, coriander,mibuna,mizuna,rocket and supreme cress all responded favourably.These herbs,apart from supreme cress,responded well to an atmosphere containing 10 per cent CO 2 and 10 per cent O 2 .Supreme cress appeared to be injured by CO 2 levels above five per cent and responded best to the 5:3 and 5:5 (CO 2 :O 2 )atmospheres.

    In addition,chervil and continental parsley stored as well in high humidity air as under controlled atmosphere at 0 °C.Basil proved the same when stored at 10 °C.Overall,the main cause of deterioration during controlled atmosphere storage was leaf yellowing,soft rots and suspected high carbon dioxide injury.

    There were similar results from the MAP trials. In general,all herbs (with exception of basil) stored longer at the lower temperature of 4 °C and benefited from atmosphere modification.

    The BOPP packaging appeared to have little effect on the storage life of basil,as it performed just as well in high humidity air.This was also true for basil in controlled atmosphere storage at 0 °C.

    But the results from the modified atmosphere packaging trial were inconclusive,so no definite recommendations are made and further trials need to be carried out to determine the best possible atmosphere and packaging for each herb.

    Field and storage trials,initiated at the request of the herb industry,were conducted on two herbs – mibuna and mizuna – to determine if field sprays had an effect on the breakdown of produce in storage.

    The industr y felt that integrated pest management strategies being adopted for the control of diamond back moth (Plutella xylostella),which relied heavily on the use of Bt and Permethrin (a biological and a synthetic insecticide respectively)were causing loss of qualit y and rapid deterioration of produce after har vest.

    In this trial,the herbs were grown under similar conditions,during which time they were sprayed with either Bt or Permethrin according to usual practices for the control of Plutella.

    The herbs were hand harvested and packed in high humidity air bags and stored under different temperatures to determine whether temperature management had an effect on the rate of deterioration.

    Results of the experiment clearly showed that the use of Bt and Permethrin had no deleterious effect on the product quality under any of the temperature regimes tested.

    In the next part of this experiment,storage trials were conducted on a mesclun salad herb mix to determine what effect storage temperature and packaging had on product market quality.

    The salad mix contained the leafy herbs mibuna and mizuna and the fancy lettuce cultivars of red coral,red oak and red minuette as well as baby bok choy leaves.It was stored at 0 °C,5 °C or 10 °C for 14 days in perforated or non perforated BOPP bags,creating a high humidity air or modified atmosphere environment respectively.

     Percentage rots of each mesclun salad mix component stored for 14 days at 0 °C,5 °C and 10 °C in perforated or non-perforated packs.Values represent ([component rot weight/component total weight ] x 100)).

    There was no significant difference in product quality between pack types.This suggests that the atmosphere modification which took place within the non-perforated bags had no beneficial effect,possibly due to the high carbon dioxide and low oxygen levels it created (17%:0%respectively).

    All herbs showed less signs of deterioration at the lower temperatures,namely 0 °C.It is therefore recommended that storage at 0 °C in perforated bags would be most beneficial and safest,as the BOPP bags created anaerobic conditions at the higher temperatures.

    Summary

    Demand is increasing for freshly harvested culinary herbs.But their extreme perishability and short shelf life has resulted in high levels of wastage and a poor quality product which has limited the commercialisation and growth of local and export markets.

    This project focused on determining optimum postharvest handling and packaging technologies to minimise quality loss and add value to eight major,fresh culinary herbs.Results have been used to develop generic postharvest handling and packaging protocols for herbs.

    Included are findings that coriander,continental parsley,mibuna,rocket and supreme cress respire less at 0 °C and 3 °C.They suffer less leaf yellowing and soft rot when stored below 4 °C.

    Coriander,continental parsley,mizuna and rocket all respond well to controlled atmospheres containing 10 per cent C0 2 and 10 per cent 0 2 .Supreme Cress responds best to the 5:3 and 5:5 C0 2 atmospheres.

    Chervil and continental parsley store as well in high humidity as in controlled atmospheres.

    These and other results of the research will help the Australian herb industry develop its own specific protocols to improve shelf life and reduce wastage.

    Proper postharvest handling and packaging methods will help secure the supply of fresh quality herbs and will assist in capturing niche and developing markets for those who can supply sufficient quantities of quality product.
     

    Other related RIRDC reports: