Pittaya Sruamsiri

Yield and quality of pectins extractable from the peels of Thai mango cultivars depending on fruit ripeness

Pectins, recovered from the peels of four mango ( Mangifera indica L.) cultivars by mimicking industrial techniques, were evaluated in terms of yield, composition, macromolecular properties, and technofunctional quality. Freeze-dried peels of mature-green fruits, after major mesocarp softening, and at full ripeness were extracted using hot acid. The pectins were precipitated in propan-2-ol and their crude yields quantified as alcohol-insoluble substance. Like apple pomace, the dried peels provided hardly acetylated (DAc < 6.3%) rapid-set to ultrarapid-set high-methoxyl pectins at starch-adjusted yields of 11-21 g/100 g. However, despite similar high molecular weight fractions and galacturonic acid/rhamnose ratios, their average molecular weight was markedly reduced by a characteristic, almost monodisperse fraction of 16000-19000. Expanded galactans, indicated by galactose/rhamnose ratios of 15-24 mol/mol, probably represented arabinogalactan side-chain fragments withstanding hot-acid extraction at pH 1.5 and 2.0, as implied by arabinose/galactose ratios of 8-15 and 33-56 mol/100 mol, respectively. Limited galacturonic acid contents made the mango peel pectins less valuable than commercial apple pectins with regard to gelling capacity and thickening properties. Whereas starch and matrix glycan fragments almost completely degraded during ripening, depolymerization of pectins and galactans was insignificant. Technofunctional properties, modulated by extraction at different pH values, were ascribed to structural differences influencing macromolecular entanglements.

The Control of Postharvest Ripening Processes and its Implications for the Productivity of Mango Processing

The production of high-quality food depends not only on an appropriate processing technology but also on the selection of proper raw materials. This experience, well known among food manufacturers, can be exemplified in the case of mango processing.

The Plant-Physiological Basis of Flower Induction in the Control of Fruit Production

In the last four years, research has focused on off-season flower induction of longan, lychee and mango trees (Chapter 3.3). In order to achieve control over the flower induction process of fruit trees, it is necessary to address the key factors responsible for the transition from vegetative to generative bud development. Various, partly competing theories have been developed in the past about the physiological ‘Who’s Who’ in flower induction (Bernier et al., 1993). One theory favours the role of carbohydrates, which need to be present in sufficient amounts as a prerequisite for flower induction (Sachs, 1977). Other theories of flower induction focus either on the genetic control of a developmental switch from vegetative to generative development (Levy and Dean, 1998), control by particular hormones (Bernier et al., 2002), the existence of specific promoting or inhibiting factors or a mixture of both. However these theories do not apply to adult perennial fruit trees (Goldschmidt and Samach, 2004). Knowledge and understanding of the hormonal changes associated with the treatments previously described (Chapter 3.3) can be beneficial for future trials to induce flowering in mango, lychee and other fruit trees.

Strategies for Flower Induction to Improve Orchard Productivity: From Compensation of Alternate Bearing to Off-Season Fruit Production

Due to alternate and irregular bearing of fruit trees, which occurs at various extent amongst different species and cultivars, the yield of many species of fruit tree is erratic. Uncertainties regarding the time of harvest and the quality and quantity of fruit can seriously affect the marketability of the product (Monselise and Goldschmidt, 1982; Westwood, 1995; Subhadrabandhu, 1999; Souza et al., 2004). Unfavourable climatic conditions during flower induction (FI) or the flowering period are amongst the most important causes of this phenomenon. Often large areas or even whole countries face the same problem simultaneously leading to overproduction and low prices in one year and a low return from fruit production the next. Equalising these fluctuations therefore would help to make fruit production more profitable and sustainable. Another option for raising the return from fruit production would be to extend or totally shift the harvest season by artificially influencing conventional and off-season flowering.

Synthesis: Food Safety, Productivity and Environmental Awareness as Key Objectives in Sustainable Fruit Production and Processing Systems

Research discussed in this chapter provides basic knowledge on characteristics of local fruit cultivars and the quality of products thereof. Participatory research approaches were extensively used and valuable in identifying constraints and research needs, but also limited as cooperation and openness of interview partners differed widely. The three fruit species of interest, mangoes (Mangifera indica L.), lychees (Litchi chinensis Sonn.) and longans (Dimocarpus longan Lour.), were investigated in parallel. Experimental research focused on: (1) Stabilising and extending the availability of fruits by overcoming alternate bearing of the fruit trees (2) Adjusting utilisation strategies for the above fruit species, aiming at diversification to meet natural heterogeneity in fruit size and quality.

Stabilisation of Fruit Production by Optimised Plant Nutrition

In the orchards of small-scale farmers in northern Thailand, low input of fertiliser often results in insufficient, low quality fruit yields particularly from older trees. This generally low input of fertilisers and other agrochemicals has been well documented. Deficiencies of micronutrients such as boron (B) and zinc (Zn) have also been frequently reported for Southeast Asia (Dong et al., 1997; Bahadur et al., 1998) and might affect flower induction, fruit set and fruit growth.