A review on TiO2-based photocatalytic systems applied in fruit postharvest: Set-ups and perspectives

Inhibition mechanism of fusarium graminearum growth by g-C3N4 homojunction and its application in barley malting

The increase of deoxynivalenol (DON) caused by Fusarium graminearum (F. graminearum) during the malting process is a serious safety problem. In our work, the inhibition mechanism of F. graminearum growth by g-C3N4 homojunction and its application in barley malting were studied. The reason why the growth activity of F. graminearum decreased after photocatalysis by g-C3N4 homojunction was that under visible light irradiation, a large amount of •O2- elicited by g-C3N4 homojunction destroyed the cell structure of F. graminearum, leading to the deficiency of cell membrane selective permeability and serious disorder of intracellular metabolism. The application of photocatalysis technology in malting can effectively inhibit the growth of F. graminearum and the accumulation of ergosterol was reduced by 30.55 %, thus reducing the DON content in finished malt by 31.82 %. Meanwhile, the physicochemical indexes of barley malt after photocatalytic treatment still met the requirements of second class barley malt in Chinese light industry standard QB/T 1686-2008. Our work provides a new idea for the control of fungal contamination in barley malt.

Latest avenues on titanium oxide-based nanomaterials to mitigate the pollutants and antibacterial: Recent insights, challenges, and future perspectives

Titanium oxide-based nanomaterials (TiOBNs) have been widely utilized as potential photocatalysts for various applications such as water remediation, oxidation, carbon dioxide reduction, antibacterial, food packing, etc. The benefits from TiOBNs for each application above have been determined as producing the quality of treated water, hydrogen gas as green energy, and valuable fuels. It also acts as potential material protecting foods (inactivation of bacteria and removal of ethylene) and increases shelf life for food storage. This review focuses on recent applications, challenges and future perspectives of TiOBNs to inhibit pollutants and bacteria. Firstly, the application of TiOBNs to treat emerging organic contaminants in wastewater was investigated. In particular, the photodegradation of antibiotics pollutants and ethylene using TiOBNs are described. Secondly, applying TiOBNs for antibacterial to reduce disease, disinfection, and food spoiling has been discussed. Thirdly, the photocatalytic mechanisms of TiOBNs to mitigate organic pollutants and antibacterial were determined. Finally, the challenges for different applications and future perspectives have been outlined.

Efficient Inhibition of Aspergillus flavus to Reduce Aflatoxin Contamination on Peanuts over Ag-Loaded Titanium Dioxide

Peanuts are susceptible to aflatoxins produced by Aspergillus flavus. Exploring green, efficient, and economical ways to inhibit Aspergillus flavus is conducive to controlling aflatoxin contamination from the source. In this study, Ag-loaded titanium dioxide composites showed more than 90% inhibition rate against Aspergillus flavus under visible light irradiation for 15 min. More importantly, this method could also reduce the contaminated level of Aspergillus flavus to prevent aflatoxins production in peanuts, and the concentrations of aflatoxin B1, B2, and G2 were decreased by 96.02 ± 0.19%, 92.50 ± 0.45%, and 89.81 ± 0.52%, respectively. It was found that there are no obvious effects on peanut quality by evaluating the changes in acid value, peroxide value, and the content of fat, protein, polyphenols, and resveratrol after inhibition treatment. The inhibition mechanism was that these reactive species (•O2−, •OH−, h+, and e−) generated from photoreaction destroyed cell structures, then led to the reduced viability of Aspergillus flavus spores. This study provides useful information for constructing a green and efficient inhibition method for Aspergillus flavus on peanuts to control aflatoxin contamination, which is potentially applied in the field of food and agri-food preservation.

Heterogeneous photocatalytic oxidation for the removal of organophosphorus pollutants from aqueous solutions: A review

Organophosphorus pollutants (OPs), which are compounds containing carbon‑phosphorus bonds or phosphate derivatives containing organic groups, have received much attention from researchers because of their persistence in the aqueous environment for long periods of time and the threat they pose to human health. Heterogeneous photocatalysis has been widely applied to the removal of OPs from aqueous solutions due to its better removal effect and environmental friendliness. In this review, the removal of OPs from aqueous matrices by heterogeneous photocatalysis was presented. Herein, the application and the heterogeneous photocatalysis mechanism of OPs were described in detail, and the effects of catalyst types on degradation effect are discussed categorically. In particular, the heterojunction type photocatalyst has the most excellent effect. After that, the photocatalytic degradation pathways of several OPs were summarized, focusing on the organophosphorus pesticides and organophosphorus flame retardants, such as methyl parathion, dichlorvos, dimethoate and chlorpyrifos. The toxicity changes during degradation were evaluated, indicating that the photocatalytic process could effectively reduce the toxicity of OPs. Additionally, the effects of common water matrices on heterogeneous photocatalytic degradation of OPs were also presented. Finally, the challenges and perspectives of heterogeneous photocatalysis removal of OPs are summarized and presented.

Effect of Nano-TiO2 Composite on the Fertilization and Fruit-Setting of Litchi

Titanium dioxide nanoparticles (nTiO₂) are widely used as fertilizers in agricultural production because they promote photosynthesis and strong adhesion. Low pollination and fertilization due to rainy weather during the litchi plant's flowering phase result in poor fruit quality and output. nTiO₂ would affect litchi during the flowering and fruiting stages. This study considers how nTiO₂ affects litchi's fruit quality and pollen viability during the flowering stage. The effects of nTiO₂ treatment on pollen vigor, yield, and fruit quality were investigated. nTiO₂ effectively improved the pollen germination rate and pollen tube length of litchi male flowers. The germination rate reached 22.31 ± 1.70%, and the pollen tube reached 237.66 μm in the 450 mg/L reagent-treated group. Spraying with 150 mg/L of nTiO₂ increased the germination rate of pollen by 2.67% and 3.67% for two types of male flowers (M1 and M2) of anthesis, respectively. After nTiO₂ spraying, the fruit set rates of 'Guiwei' and 'Nomici' were 46.68% and 30.33%, respectively, higher than those of the boric acid treatment group and the control group. The edibility rate, titration calculation, and vitamin C of nTiO₂ treatment were significantly higher than those of the control. The nTiO₂-treated litchi fruit was more vividly colored. Meanwhile, the adhesion of nTiO₂ to leaves was effectively optimized by using ATP and BCS to form nTiO₂ carriers and configuring nTiO₂ complex reagents. These results set the foundation for future applications of titanium dioxide nanoparticles as fertilizers for agriculture and guide their application to flowers and fruits.

Advances on removal of organophosphorus pesticides with electrochemical technology

Widespread use of organophosphorus pesticides (OPs), especially superfluous and unreasonable use, had brought huge harm to the environment and food chain. It is because only a small part of the pesticides sprayed reached the target, and the rest slid across the soil, causing pollution of groundwater and surface water resources. These pesticides accumulate in the environment, causing environmental pollution. Therefore, in recent years, the control and degradation of OPs have become a public spotlight and research hotspot. Due to its unique advantages such as versatility, environmental compatibility, controllability, and cost-effectiveness compatibility, electrochemical technology has become one of the most promising methods for degradation of OPs. The fundamental knowledge about electrochemical degradation on OPs was introduced in this review. Then, a comprehensive overview of four main types of practical electrochemical technologies to degrade pesticides were presented and evaluated. The knowledge contained herein should conduce to better understand the degradation of pesticides by electrochemical technology, and better exploit the degradation of pesticides in the environment and food. Overall, the objective of this review is to provide comprehensive guidance for rational design and application of electrochemical technology in the degradation of OPs for the safety of the environment and food chain in the future.

Photoactivated TiO2 Nanocomposite Delays the Postharvest Ripening Phenomenon through Ethylene Metabolism and Related Physiological Changes in Capsicum Fruit

Capsicum is one of the most perishable fruit which undergo rapid loss of commercial value during postharvest storage. In this experiment our aim is to evaluate the effect of photoactivated TiO₂ nano-particle complexed with chitosan or TiO₂-nanocomposite (TiO₂-NC) on extension self-life of Capsicum fruit and its effect on related morphological, physiological and molecular attributes at room temperature (25 °C). Initially, TiO₂-NC coated fruits recorded superior maintenance of total soluble solids accumulation along with retention of firmness, cellular integrity, hydration, color etc. On the extended period of storage, fruit recorded a lower bioaccumulation of TiO₂ in comparison to metallic silver over the control. On the level of gene expression for ethylene biosynthetic and signaling the TiO₂-NC had more regulation, however, discretely to moderate the ripening. Thus, ACC synthase and oxidase recorded a significantly better downregulation as studied from fruit pulp under TiO₂-NC than silver. On the signaling path, the transcripts for CaETR1 and CaETR2 were less abundant in fruit under both the treatment when studied against control for 7 d. The reactive oxygen species (ROS) was also correlated to retard the oxidative lysis of polyamine oxidation by diamine and polyamine oxidase activity. The gene expression for hydrolytic activity as non-specific esterase had corroborated the development of essential oil constituents with few of those recorded in significant abundance. Therefore, TiO₂-NC would be reliable to induce those metabolites modulating ripening behavior in favor of delayed ripening. From gas chromatography-mass spectrometry (GC-MS) analysis profile of all tested essential oil constituents suggesting positive impact of TiO₂-NC on shelf-life extension of Capsicum fruit. Our results indicated the potentiality of TiO₂-NC in postharvest storage those may connect ethylene signaling and ROS metabolism in suppression of specific ripening attributes.

The Emergence and Impact of Ethylene Scavengers Techniques in Delaying the Ripening of Fruits and Vegetables

As the top grocery list priorities, the primary challenge when purchasing fruits and vegetables from supermarkets is obtaining fresh, minimally processed perishable goods. This source of diet is critical for obtaining vitamins, minerals, antioxidants, and fibres. However, the short shelf life caused by moisture content in rapid deterioration and decay caused by microbial growth, results in unappealing appearances. Fruits and vegetables undergo ripening and eventually the ageing process, in which the tissues of the plants degrade. Even after harvesting, numerous biological processes occur, generating a significant variation of ethylene production along with respiration rates between fruits and vegetables. Thus, the utilization of ethylene scavengers in food packaging or films has been revealed to be beneficial. The synergistic effects of these biomaterials have been demonstrated to reduce microorganisms and prolong the shelf life of greens due to antimicrobial activity, oxygen scavenging capacity, enzyme immobilization, texture enhancers, and nutraceuticals. The current review fills this void by discussing the most recent advances in research on ethylene scavengers and removal mechanisms of ethylene, including oxidation in fruit and vegetable packaging. The application and advantages of ethylene scavengers in packaging are then discussed with the addition of how the efficiency related to ethylene scavengers can be increased through atmospheric packaging tools. In this context, the article discusses characteristics, types of applications, and efficacy of ethylene control strategies for perishable commodities with the inclusion of future implications.

Physiological changes in green and red cherry tomatoes after photocatalytic ethylene degradation using continuous air flux

In this work photocatalytic ethylene degradation (TiO₂-UV) was applied in green cherry tomatoes with the aim to control biochemical and physiological changes during ripening. Photocatalytic process was performed at 18 °C  ±  2 °C and 85% HR for 10 days using continuous air flux. Ethylene, O₂ and CO₂ concentration from cherry tomatoes under TiO₂-UV and control (c) fruits, were measured by GC-MS for 10 days. After that, the tomatoes were stored for 20 days. During the photocatalysis process, ethylene was completely degraded and control fruits, the ethylene was 28.73 nL g^-1. Respiration rate was lower for fruits under TiO₂-UV than control. During storage period, cherry tomatoes treated by TiO₂-UV, showed lower ethylene concentration, respiration rate, total soluble solid, lycopene, sugar and organic acid content than control showing that the fruits treated with photocatalysis did not reach the full maturity. In addition, all the cherry tomatoes showed different maturity stages. Fungal incidence was higher in control fruits than fruits treated with photocatalysis. This research showed for the first time that photocatalytic technology preserved the physiological quality of cherry tomatoes for 30 days of storage, being a promised technology to preserve cherries tomatoes.