Top Of Fruit Research Articles

Differences of reactive oxygen species metabolism in top, middle and bottom part of epicarp and mesocarp influence tomato fruit cracking

ABSTRACT Tomato (Solanum lycopersicum L.) fruit cracking is a serious economic problem, affecting fruit quality and yield. During abiotic stress, the imbalance of reactive oxygen species (ROS) metabolism causing membrane damage might increase the susceptibility of pericarp to changing environment and then affect fruit cracking. To further validate the relationship between ROS metabolism and fruit cracking, we used cracking-resistant tomato ‘LA1698’ and cracking-susceptible tomato ‘LA2683’ as test materials. ROS, membrane lipid peroxidation, antioxidants and soluble protein in different parts (top, middle and bottom) of epicarp and mesocarp were studied. Results showed that, the highest ROS levels and membrane lipid peroxidation degree were observed in the top of epicarp in ‘LA2683’. Moreover, ‘LA2683’ displayed lower superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR) activity and ascorbic acid (AsA) content, and maintained higher polyphenol oxidase (PPO), peroxidase (POD), catalase (CAT) activity and soluble protein content in each part of epicarp, compared with ‘LA1698’. In conclusion, the top of epicarp in ‘LA2683’ accumulated higher ROS, concurrent with decreased ROS scavenging ability, and the disordered ROS homoeostasis led to cellular oxidative damage, which could effect the occurrence of cracking at the top of fruit. ROS metabolism in epicarp may play an important role in fruit cracking.

PHYSICAL AND MECHANICAL PROPERTIES OF PONKAN MANDARIN APPLIED TO GRADING MACHINE

The aim of this research is to study some physical and mechanical properties of Ponkan mandarin, as promising fruits, to help the design of handling machines. The physical and mechanical properties are incorporated in the development of the grading machine as a case study. The main results in this study can be summarized in the following points: Physical properties of Ponkan mandarin fruits: diameter = 58.61 – 85.56 mm, height = 49.45 – 78.9 mm, mass = 70 - 128 g, volume = 60 - 120 cm3, projected area = 41.22 – 81.88 cm2, peel thickness = 2.18 – 3.73 mm, peel mass = 24.2 – 36.1 g, number of segments/fruit = 8 - 12, number of seeds/fruit = 4 - 9, juice volume/fruit = 23 - 34 cm3, and juice volume/fruit mass = 0.24 - 0.45 L/kg. Mechanical properties of Ponkan mandarin: The average of firmness distribution along Ponkan mandarin surface were: the maximum = 18.3 N/cm2 at the top of fruit and the minimum = 11 N/cm2 at the bottom of fruit. The deformation range increased from 2.75 - 3.09 to 8.52 - 10.02 mm by increasing loading from 1 to 5 kg. Meanwhile, the deformation range increased from 2.75 - 8.52 to 3.09 - 10.02 by increasing loading time from 15 to 60 s. Some application to grading machine is given also in the paper as a case study.