AGRE-0058 Advanced and Innovative Technologies for the Citrus Fruit Industry

SUMMARY

This broad-based project covered a wide range of activities associated with processing of citrus fruit, as well as other parts of the plant, extending to waste water purification. The main activity of interest, apart from those relating to the direct processing of the fruit for juice or segments, covered the development of supercritical fluids extraction processes for the production of essential oils from parts of the citrus tree. Other aspects of the project covered the selection of efficient and economic systems for waste water treatment and recycling as well as development of methods of analysis of citrus products and by-products.

INTRODUCTION

This project examined a number of aspects relating to the processing of citrus fruit, and other parts of the tree, for both direct consumption (juice, segments) and the production of flavours and fragrances.

OBJECTIVES

One of the main objectives was to investigate the extraction of essential oils from the fruit and various other parts of citrus trees using supercritical carbon dioxide. The activities extended from definition of experimental parameters for optimal extraction to design of possible equipment to achieve the required extraction.

ACTIVITIES

Essential oils and other fractions: Extraction tests were carried out at a carbon dioxide density range between 0.50 and 0.82 kg/l, at either 40 or 50ºC. Waxes co-extracted with the essential oils created some problems in separation. However, systems were designed to overcome this problem. Various methods were used to treat or infuse fruit with various commercial enzymes as a means of removing peel. This and other activities, including application of ultrafiltration membranes and resins for clarification and debittering/decolouring, enabled extraction of lomonin and anthocyanins. Characteristics of the samples were measured according to internationally accepted methods for essential oils (International Organisation for Standardisation). In addition, new methods of analysis were developed for the determinations of anthocyanins and limonin and the chromatographic evaluation of the essential oils.

Effluent treatment: For waste treatment, a system divided into three sections (collection, oxidation and sludge settling) was complemented by a further stage for drainage and partial sludge dehydration as well as two subsequent stations for the treatment of purified waters (chlorinating and decolouration/deodourisation). This plant differs from traditional active sludge plant by the addition of a static "percolator filter" positioned upstream from the oxidation phase, through which part of the water from the collecting basin is recycled. The test carried out involved the development of the system and a comparison of results obtained with or without the "percolator" stage. The whole plant was automated, including the system controlling the introduction and regulation of effluent flow, control of pH, transfer of water from one sector of the plant to the next and the discharging of sludge.

RESULTS

Extractions using supercritical carbon dioxide, which obtained essential oils from twigs, leaves, blossoms and flowers of mandarin, gave products with colours and fragrances that differed from those obtained by distillation. These extracts could be classified as a new essence.

The use of enzymes to treat peeled segments gave a product which had a flavour which was "pleasant and natural" in comparison to chemically peeled segments. Although resin processes proved satisfactory these, unlike in the USA, are still not recognised in the EU and, therefore, cannot be adopted in the citrus industries of European Union countries. It might be hoped that existing legislation be revised by the competent EU Authorities so as to include in Article 4 of Directive 93/77, the recognition of adsorbent resins which have been shown to be chemically inert, as have already been recognised by the FDA as valid in treatment processes of citrus juices.

For effluent treatment, the process studied was satisfactory resulting in a significant reduction of pollution from the first phase of citrus process at fairly modest running costs. However, further work is required to produce a final effluent which complies with existing regulations for possible re-use in industry as process water.

COMMERCIALISATION

Further work is still required to define the best parameters for a number of these activities, including optimisation of the waste water treatments and enzyme technologies. As far as the resin treatments are concerned, the technology is ready to be applied in citrus industries, apart from the fact that EU legislation does not allow their use.

PARTICIPANTS

CEBAS-CSIC (Murcia, Spain), NARF-ITAP (Lykovrissi, Greece), Citrag Ricerche Srl (Messina, Italy), FDT Depuratori d'acqua (Brugherio, Italy), SSIA (Reggio Calabria, Italy).