Quantitative Analysis by HPLC and FT-MIR Prediction of Individual Sugars from the Plum Fruit Harvested during Growth and Fruit Development

Romina Vlaic,Georgiana Petruț,Vlad Mureșan,Andruța Mureșan,Crina Mureșan,Sevastiţa Muste

doi:10.3390/agronomy8120306

Abstract

Individual sugars were analyzed by High Performance Liquid Chromatography (HPLC) in plum juice samples obtained from “Stanley”, “Vânăt de Italia”, and “Tuleu Gras”. The samples were harvested from the inside and periphery of the crown during six development phases. The aim of the present study was to determine the individual sugars in plum juice by the HPLC and Fourier transform mid-infrared spectroscopy (FT-MIR) methods and to validate them. Our findings were as follows: levels between 0.26–3.73% for fructose, 1.43–1.10% for glucose, and 0.01–10.19% for sucrose. The FT-MIR analyses confirmed the differences between the juice samples, mainly in the spectral region characteristic to sugars which ranged from 900 to 1500 cm−1. FT-MIR coupled with Partial least squares (PLS) was used to develop calibration models for estimating individual plum juice sugars, the predictive characteristics being assessed. The optimal regions and spectral pretreatments were 800–1600 cm−1 and Savitzky Golay first derivative (d1) for fructose, 800–1600 cm−1 for glucose, and 915–1145 cm−1 and second derivative (d2) for sucrose. The selection of optimal spectral zones and pre-treatments led to PLS calibration models with acceptable predictive abilities for glucose, very good for sucrose, and less satisfactory for fructose. Moreover, the FT-MIR results were compared to the HPLC results in external validation tests and reference values included.

Highlights

In countries of the European Union, more than 190 thousand hectares are cultivated withPrunus domestica L., which is one of the preferred plum trees, in this part of the world
The aim of the present study was to determine the individual sugars in plum juice by the High Performance Liquid Chromatography (HPLC) and Fourier transform mid-infrared spectroscopy (FT-MIR) methods and to validate them
During the growth and development of plums, the glucose levels reached a peak in the first developmental phases, while the sucrose values were lower than 0.02 g/100 g of juice

Summary

Introduction

In countries of the European Union, more than 190 thousand hectares are cultivated withPrunus domestica L., which is one of the preferred plum trees, in this part of the world. The EU production (1.6 million tonnes) of Prunus domestica plums constitutes 15% of the global production of this fruit [1]. As it is so highly appreciated by consumers all over the world, this fruit species has become outstandingly popular [2]. The carbohydrates contained in the fruit provide energy to consumers; the sweetness of the fruit enhances consumers’ pleasure while eating it, determining the edibility of the fruit [4]. During growth and development plants need soluble sugars for reaching complete maturity [5]. Accumulation of soluble sugar during the fruit development causes the sweetness when the fruit is ripe and ready for harvest.

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Conclusion