Cytological aspects of Butia capitata (Arecaceae) fruit maturation and senescence

The fruits of several palm species are rich in nutrients and widely used in food industries, but little is known concerning their maturation and senescence. We related physicochemical indicators and cytological alterations associated with the maturation and senescence of the fruit pulp of the neotropical palm Butia capitata, whose sweet-acidic juice is used in the manufacture of beverages and ice cream. Morphological, physicochemical, histochemical, and ultrastructural evaluations of ripening and post-harvest fruits were performed. During maturation, the pulp cells store mucilage, sugars and organic acids in the vacuole, starch and carotenoids in the plastids, and lipids and proteins in the cytosol. The physiological maturity of the pulp is reached at the moment of abscission (= harvest point), approximately 90 days after anthesis. The fruits have a yellow-orange (maximum accumulation of carotenoids), succulent, fibrous, and soft (weakening of the median lamellae and cell walls) aspect at that time, with reduced phenolic contents in the vacuoles and high levels of soluble solids (SS) (derived from the degradation of starch into sugars). The pulp of the ripe fruits is composed of carbohydrates (77%), lipids (16%), proteins (3%), and carotenoids (3728 µg 100 g−1), and the juice has a pronounced acidity (pH 3.3). Pulp senescence is related to a decline in acidity (TA), an increase in SS and the SS/TA ratio, reduction in firmness (loosening of cell walls), reductions of nutrient levels, and increased phenolic accumulations, culminating in protoplast collapse. A cytological model useful for understanding the maturation and senescence of sweet-acidic pulps is proposed.