Studies on the preservation of flowers
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A known method for the preservation of green foliage was adapted in order to preserve floral tissues, retaining the colour and texture, thereby providing a method suitable for the preservation of whole flowers. Initially, the effects of the existing foliage preservation process on floral tissues were studied and the resulting problems of limp sticky petals and colour loss were identified. Subsequently, with a knowledge of basic plant anatomy and of the properties of the main floral pigments, the anthocyanins, a series of experiments on petals and whole flowers were carried out in an attempt to rectify these problems and to incorporate the remedies into a method for preserving whole flowers. The problem of improving the texture and firmness of flower heads was tackled by investigating the effects of adding bulking or setting ingredients to the process fluid and establishing their optimum concentrations. In the case of flower colour, the addition of acid was required in order to maintain the bright anthocyanin colours and a range of acids was investigated. Furthermore, since it is known that in nature the anthocyanin pigments are stabilised by metal ions and copigments, the use of these agents in the preservation process was also considered. This empirical work was then validated by confirming the identity of the main pigments involved and by studying various aspects of the new preservation process. Factors examined included acid concentration, temperature, solvent composition and the addition of metal ions and copigments to solutions of petal extracts containing anthocyanin pigments. Physical changes resulting from processing, including process fluid content and the moisture absorption properties of processed petals were also measured. Finally, the application of a selection of coating materials was assessed in an attempt to increase the life span of the processed flowers by providing extra protection against environmental stresses.
Thesis, PhD Doctor of Philosophy
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