Post-harvest sugar-acid balance and sensory quality of pineapple fruit as affected by pre-harvest plant spacing and growth regulator application

Abstract:

Packhouse rejection rates for MD2 pineapple in Brazil's Recôncavo Baiano region frequently exceed 20 %, driven less by external defects than by internal quality shortfalls-fruit that looks acceptable but tastes flat or excessively sour. Whether pre-harvest management of plant spacing and Gibberellic Acid (GA₃) application can shift the sugar-acid balance toward the sensory sweet-spot demanded by export markets has received limited experimental attention on acid lowland soils. This research evaluated three plant spacings-high density (HD, 25 × 50 cm, 65,000 plants ha⁻¹), standard density (Std, 30 × 60 cm, 43,500 plants ha⁻¹), and Low Density (LD, 40 × 60 cm, 33,000 plants ha⁻¹)-with and without a foliar GA₃ spray (50 mg L⁻¹ at 30 days before anticipated harvest), in a 3 × 2 factorial RCBD with four replications on an Ultisol (pH 4.4) at Cruz das Almas, Bahia, from April 2020 to August 2021. Fruit were assessed for Total Soluble Solids (TSS), Titratable Acidity (TA), TSS/TA ratio, individual sugars (sucrose, glucose, fructose by HPLC), and sensory attributes (9-point hedonic scale, 30 semi-trained panellists). TSS ranged from 13.2 °Brix (HD, no GA₃) to 16.1 °Brix (LD + GA₃), and TA from 0.44% (LD + GA₃) to 0.71% (HD, no GA₃). The TSS/TA ratio-the strongest predictor of consumer sweetness perception-was highest in LD + GA₃ (36.6) and lowest in HD without GA₃ (18.6). Sensory overall acceptability mirrored these chemical trends, scoring 8.1 for LD + GA₃ versus 6.0 for HD. GA₃ application raised TSS by 1.0-1.6 °Brix and lowered TA by 0.07-0.13 percentage points across all spacings. These findings indicate that wider spacing combined with pre-harvest GA₃ treatment can raise internal quality to premium-export thresholds on acid soils, offering a practical lever for Brazilian smallholders to capture price premiums.