Hiroaki Kitazawa

Effects of Various Asparagus Production Methods on Rutin and Protodioscin Contents in Spears and Cladophylls

The purpose of this study was to clarify the relationship between various cultivation conditions and the amounts of the rutin (RT) and protodioscin (PD) in asparagus spears. Green and white spears were grown in open culture and under two different blanching conditions. Although RT was detected only in the green spears, PD was detected mainly in white spears produced by covering with soil. The RT and PD contents of cladophylls grown in an open field and in a closed cultivation system were also investigated, and the closed system resulted in cladophylls with low RT and high PD, unlike the open field.

Nanoreinforcement of Pectin Film to Enhance its Functional Packaging Properties by Incorporating ZnO Nanoparticles

The main objective of this study was to enhance functional packaging properties of pectin film by using zinc oxide nanoparticles (ZnO-NPs) as nanoreinforcing agent. Pectin/ZnO bio-nanocomposite films were fabricated at 4 levels of ZnO-NPs, i.e., 0.5, 1.0, 2.0 and 5.0% (w/w). The effects of ZnO-NPs incorporation on improving the mechanical properties and water resistance of the films were investigated. ZnO-NPs were successfully incorporated into pectin films by nanodispersion technique followed by casting method. The presence of ZnO-NPs inside pectin films was observed clearly by SEM. The improvement in tensile strength could be achieved with ZnO-NPs incorporation without obvious loss in elasticity. Potential antimicrobial activity of pectin-ZnO nanocomposite films was proved in the absence of mold after exposing them at 97% RH and room temperature for 14 days, whereas the growth of mold had been observed in pure pectin film after 3 days of exposure. In terms of film transparency, the significant change in film opacity was only found in the film prepared with 5% of ZnO. Results suggested that it would be favorable to prepare pectin/ZnO nanocomposite film by using ZnO-NPs at the amount of 2% (w/w) in the future work.

Regulation of Respiratory Pathway and Electron Transport Chain in Relation to Senescence of Postharvest White Mushroom (Agaricus bisporus) under High O2/CO2 Controlled Atmospheres

In order to study the respiration metabolism mechanism based on the generation of adenosine triphosphate (ATP) and reactive oxygen species (ROS) and nitric oxide (NO) by the electron transport chain (ETC) of the white mushroom under high O2/CO2 controlled atmospheres, the treatments of 100% O2, 80% O2 + 20% CO2, 60% O2 + 40% CO2, and 40% O2 + 60% CO2 at 2 ± 1 °C were employed and natural air was used as the control. ATP and energy charge can maintain the membrane integrity and function, life activities, and physicochemical reactions of higher plants. The results showed that the 80% O2 + 20% CO2 treatment inhibited the respiration rate, embden-meyerhof-parnas or glycolysis pathway, and ROS and NO contents. It significantly delayed the reduction of the ATP content and energy charge level, tricarboxyfic-acid-cycle and cytochrome pathway proportion, and their key enzymes activity and gene expression. It also maintained a high phosphopentose pathway and moderate alternative pathway. Results indicated that the 80% O2 + 20% CO2 prolonged the storage time of mushrooms to 24 days and retarded the senescence through retaining the higher energy, suppressing the ROS contents, enhancing the endurance capability in adversity, and regulating the respiration pathways and ETC metabolism.

Yield estimation of 1-year-old asparagus grown using rootstock-planting forcing culture

ABSTRACT Rootstock-planting forcing culture was developed in asparagus to harvest spears even during the seasons when the plants become dormant, but the demand for them high. In this study, cumulative hours during which the air temperature remained lower than 5°C, i.e. chilling hours (CHs), were calculated to determine dormancy breakage for asparagus cultures. We also measured CIELab colour values for cut stems immediately before rootstock digging, and determined whether they could be substituted and/or compensated for CHs while evaluating asparagus plant productivity in different low-temperature backgrounds, and obtained regression equations for yield estimation. Asparagus seedlings were cultivated in seven different regions across Japan and brought to the study site for harvesting. Our regression equation based on CHs and rootstock weight for yield estimation had relatively high fitness (adjusted R2 = 0.5795). The colour values of cut stalks at rootstock digging can also be used to evaluate their productivity. These values can be useful in regions where CHs cannot be determined, although their effectiveness was slightly lower than that of CHs of areas adjacent to the study sites.

Effects of a high O2 dynamic-controlled atmosphere technology on the browning of postharvest white mushroom (Agaricus bisporus) in relation to energy metabolism:

Browning is one of the main problems in senescence of mushrooms, and it is also one of the most important attributes accounting for the loss of the quality and reduction in market value. In order to study the relationship between the energy metabolism and the browning of white mushroom under high O2 dynamic-controlled atmosphere (HO-DCA), mushrooms were stored in 100% O2 (SCA1), 80% O2 + 20% CO2 (SCA2), 100% O2 for three days and then transferred into the treatment of 80% O2 + 20% CO2 (HO-DCA) at 2 ± 1 ℃ and air as control. In this study, adenosine triphosphate (ATP) content, energy charge level, sensory evaluation, browning of surface and flesh, cell membrane integrity, exogenous ATP, polyphenol oxidase (PPO) and peroxidase (POD) activity and genes encoding PPO of the white mushroom were investigated. These were all closely related to the browning of products. The optimal storage condition of the HO-DCA treatment could delay the browning of pericarp and flesh tissues of the mushrooms, inhibit PPO activity and reduce the relative expression levels of the three genes encoding PPO. Meanwhile, it maintained moderate POD activity, good sensory properties and cell membrane integrity in a certain extent and thus slowed down the senescence of mushrooms. Results indicated that there was a positive correlation between the ATP content and whitening index (r = 0.901). In addition, HO-DCA maintained a higher ATP level, prolonged the storage time to 28 days and it might be an ideal strategy for preserving the quality of mushroom during storage.

Detection of Candidatus Liberibacter asiaticus from branch collars of citrus trees

Candidatus Liberibacter asiaticus (Las) is a causal agent of citrus greening disease (CG; Huanglongbing) in Japan. Currently, the midribs of leaves are used to diagnose CG-infected trees. In this study, we sampled branch collars of trees to test for Las. The pathogen was identified more often in the shoot bases than in the petioles, midribs, or shoot tips. Las concentration in branch collars was the highest at the shoot bases. In branch collars, the Las concentration in the cortical tissues was higher than in the pith. The cortex of branch collars can be used to diagnose CG-infected trees. In addition, Las could be detected from dying trees in the branch collar cortex. Therefore, CG infection can be diagnosed in trees that do not produce leaves. In addition, a detection limit was determined when the branch collar cortex from one infected tree was mixed with those from multiple healthy trees. As a result, the pathogen could be detected in an infected tree when the cortex of a single infected tree was mixed with those of nine healthy trees. Based on this result, 10 trees can be assayed together to determine the incidence of CG in Japan.

Application and Simplification of Cell-Based Equivalent Circuit Model Analysis of Electrical Impedance for Assessment of Drop Shock Bruising in Japanese Pear Tissues

This study was conducted with the objective of applying cell-based electrical equivalent circuit analysis for the assessment of bruising of tissues in Japanese pears after drop tests, as well as to simplify the analysis. The equivalent circuit analysis of electrical impedance values was conducted on the bruised regions of the pear tissues. The analysis showed that the resistance of the protoplasm of the injured tissues slightly increases, and the capacitance of cell membranes and the resistance of apoplastic fluids significantly decrease. Thus, it was theorized that these parameters are influenced by cell membrane destruction. Further, it was found that Cole-Cole plot parameter obtained from the frequency characteristics of the impedance of the tissues can express changes in the apoplastic fluid resistance. These results show that equivalent circuit analysis can be used to assess bruising of pear cells caused by drop shock, and the analysis can be simplified using Cole-Cole plots. We expect these results to aid in the development of physical damage assessment methods for distributed fruits.

Research on energy metabolism, lignification and veil opening in postharvest white mushroom ( Agaricus bisporus ) under high O 2 /CO 2 controlled atmospheres (HOC-CA)

White mushroom is an abundant nutritional but perishable product; veil opening and stipe lignification are two of the obvious characte-ristics of senescence. In order to study the relationship between the energy charge, veil opening and lignification of the white mushroom, high O2/CO2 controlled atmospheres (HOC-CA) were utilized at 2±1 °C. The treatments comprised the following 100% O2, 80% O2 + 20% CO2, 60% O2 + 40% CO2, 40% O2 + 60% CO2 respectively, with air as the control. In this study, sensorial and physiological qualities, adenosine triphosphate (ATP) content, energy charge level, lignin content, phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD) activity were studied. The optimal condition 80% O2 + 20% CO2 treatment inhibited both respiration rate and veil opening of the mushroom; suppressed PAL, POD and CAD activity. It also retarded the reduction of ATP level, energy charge level, and growth of lignin content. Exogenous ATP had an effect on inhibiting veil opening and lignification. These results indicated that there was a negative correlation between the ATP content, cap opening and stipe lignification. Appropriate HOC-CA maintained high energy, preserved the white mushroom well and extended the storage time to 24 days.