Apple Surface Research Articles

Phytochemicals-based edible coating for photodynamic preservation of fresh-cut apples

Nature-derived chemicals have recently gained increased attention to settle down the challenges in the food industry. Quercetin has long been used as a natural medicine but its photoactivity has been neglected. In this work, by combining photodynamic bacteria inactivation (PDI) with an edible coating (Pectin/Quercetin) derived from FDA-approved chemicals, extend shelf-life and protected commercial quality of fresh-cut apples were achieved. Firstly, the potential photoactivated antibacterial performance of Quercetin (a natural plant flavonoid) was clarified with the treatment of a simulated sunlight lamp, realizing antibacterial efficacy of 100 % towards S. aureus (50 min) and L. monocytogenes (80 min) with light treatment. To develop safe and effective preservation of fresh-cut apples, Pectin/Quercetin edible coatings with 100 μmol/L quercetin were adopted. The results showed that the prepared edible coatings form a protective barrier over the surface of apples, effectively resisting bacterial infection and extending shelf life to 10 days while maintaining good commercial quality (including preferable color, keeping 100 % hardness, 80 % sugar content and 17.3 % weightlessness rate). Therefore, the prepared light-driven Pectin/Quercetin in this work has the potential to develop as fresh-cut fruit preservation technology.

Rapid determination of thiram on apple using a flexible bacterial cellulose-based SERS substrate

A flexible nanocomposite composed of bacterial cellulose (BC) and gold nanoparticles (AuNPs) was developed as a SERS substrate to determine thiram on apple surface by two collection methods namely “paste-and-peel” and “wiping”. Enhancement factor of this SERS substrate for sensing thiram residues was determined to be 2.8 × 105. Compared to the benchtop Raman spectrometer, portable Raman spectroscopic device showed a lower sensitivity towards thiram residues with limit of detection at 0.98 ppm, satisfying maximum residue level of thiram on apple required by both Europe and America. A good linear correlation of SERS peak intensity at 1368 cm−1 and different concentrations of thiram (1–50 ppm) revealed a coefficient up to 0.99. This flexible BC-based SERS substrate has a great analytical performance in sensitivity, reproducibility and stability, and is suitable for rapid detection (<8 min) and quantitative analysis of pesticides on food surface.

Development of a Novel Biomimetic Mechanical Hand Based on Physical Characteristics of Apples

For the purpose of minimizing the damage to apples during the operation of an apple-picking robot, improving the stability of an apple-harvesting mechanical hand and reducing the use and operation cost of the robot, a novel biomimetic apple mechanical hand based on negative pressure air suction is purposely designed based on the physical characteristics of apples by imitating octopus predation. The mechanical hand has four suction cups evenly distributed in the hand, which produce concave deformation under negative vacuum pressure to fit the apple surface and adsorb the apple; the fruit stalk is separated by wrist rotation and dragging in a compound way to complete the picking operation. This paper firstly determines the key parameters of the mechanical hand based on the characteristics of silicone material and the three growth postures of apples, tries to make a physical prototype of the mechanical hand and conducts relevant performance tests on the picking platform built in the laboratory to explore the best combination of parameters and further optimize the manipulator. The results show that the success rate of the biomimetic nondestructive apple picker with the best combination of parameters is 100%, 76% and 68% for three different apple-growth postures and the operation is smooth, reliable, safe and non-invasive.

Controllable assembly of high sticky and flexibility surface-enhanced Raman scattering substrate for on-site target pesticide residues detection

Pesticide residues in fruit and vegetable constitute a great threat to mankind's health, and a technique of rapid, cost-effective, ultra-sensitive and non-destructive analysis is especially critical for on-site detection in practical application. A strategy was utilized to fabricate highly viscous and flexible WPU@AgNPs sticky tape for the rapid extraction and Surface-enhanced Raman Scattering (SERS) assay of thiabendazole residues on the surface of fruits. Simply put, the novel WPU@AgNPs tapes were constructed by decorating the waterborne polyurethane (WPU) film with silver nanoparticles (AgNPs), and demonstrated excellent sensitivity with 4-Mercaptopyridine (4-Mpy) as the probe molecule. Meanwhile, the enhancement factor of the novel SERS substrate could reach 7.01 × 106, which was consistent with the finite difference time domain (FDTD) theoretical simulation results. What’s more, the high viscosity and flexibility of WPU@AgNPs sticky tapes allowed them to detect the thiabendazole residues on the pear, apple and banana surfaces by a straightforward “paste and peel off” approach. The results showed that the detection limit could reach 1.44, 1.12 and 1.63 ng/cm2. This strategy would be as a common method for prompt, on-site and ultra-sensitive assay of thiabendazole residues in chemical and biological fields.

Bruise measurement of fresh market apples caused by repeated impacts using a pendulum method

This paper presented an approach using a pendulum method to measure bruise damage of apples to overcome the limitation of the drop test on impact control on a specific fruit zone. Conditions included three impact energies (0.011, 0.042, and 0.094 J) and four repeated series (1, 3, 5, and 10) across three surface zones (top/stem shoulder, middle/cheek, and bottom/calyx shoulder) on large and small fruit. A full factorial experimental design was performed to investigate the effects of these factors on bruise damage. Twelve smaller areas separated from each zone of a pair of large/small apples and twelve treatments between the three impact energies and four repeated impact series corresponded to each other to reduce errors caused by the variance of specimens. Impact parameters (impact force and contact time), bruised area (BA), volume (BV), and susceptibility (BS, the ratio of BV to impact energy) were counted/calculated, respectively. It was demonstrated that the apple surface zone and repeated impact series could significantly affect bruise sizes and susceptibility to bruising. Results indicated that the impact force clearly increased with increased impact series before five impacts, but the increment decreased successively for every single impact, and the same was true for BA and BV, while the contrary was true for BS. More repeated impacts with lower intensity were more likely to reduce BA and BV compared to fewer impacts with higher intensity. The contact time decreased from the top to the bottom zone at both 0.011 and 0.042 J impacts. The fruit zone near the stem was more susceptible to causing smaller bruise sizes at a 0.042 J impact.

Study on the biocontrol effect and physiological mechanism of Hannaella sinensis on the blue mold decay of apples

Blue mold decay is a major postharvest disease of apples, causing considerable losses to the apple industry. In the early stage of this research, an antagonistic yeast, Hannaella sinensis, with a good control effect on the blue mold of apples, was selected. On this basis, the main purpose of this work was to study the biocontrol effect of H. sinensis on the blue mold of apples and the mechanisms involved. The results showed that H. sinensis could effectively control the blue mold decay of apples, reduce the rot rate and diameter, and the antagonistic effect strengthened with the increase of H. sinensis concentration (1 × 108 cells/mL). Further in vitro experiments proved that H. sinensis could significantly inhibit the spore germination and germ tube length of P. expansum. In addition, stable colonization of H. sinensis on apple wounds and surfaces confirmed the environmental adaptability and the ability to compete with other microbiota for nutrition and space. Moreover, H. sinensis induced the activities of resistance-related enzymes such as polyphenol oxidase (PPO), peroxidase (POD), ascorbate peroxidase (APX), superoxide dismutase (SOD), and phenylalanine ammonia-lyase (PAL) in apples and the content of the coding genes corresponding to these enzymes was also higher than that of the control group. Our results indicate that H. sinensis treatment could induce the disease resistance of apples. In summary, H. sinensis served as a promising antagonistic yeast for the prevention and treatment of postharvest blue mold decay of apples.

IODINE ABSORPTION BY APPLE LEAF SURFACES.

Apple is an important agricultural product in Aomori Prefecture, Japan, where the first commercial nuclear fuel reprocessing plant is currently under construction. As the behavior of radioiodine deposited on the surface of apple leaves is not well known, we studied the absorption and transfer to fruit of stable iodine applied onto the leaf surface. Droplets of NaI solution were applied to the leaf surface $\sim$86-89days after flowering. The leaves were collected periodically and washed with detergent solution, followed by determination of iodine amounts absorbed or remaining on the leaf surface. Subsequently, iodine levels were determined separately for each part of the apple tree. Our results indicated that iodine applied on the surface of the leaf was absorbed and accumulated inside the leaf, but the transfer of absorbed iodine to the fruit was negligible; hence, iodine was less likely to accumulate in the fruit.

Novel fungal organophosphorus hydrolases in acidic media: an application to apples decontamination.

Organophosphorus pesticides bring significant improvements in agriculture, but their toxicity causes environmental and health negative impacts. The aim of this work was the development of robust biocatalysts to be applied in bioremediation. Four fungi were evaluated as hydrolase sources capable of degrading organophosphorus pesticides: Aspergillus niger, Fusarium sp., Penicillium chrysogenum, and Penicillium nalgiovense. The hydrolysis rates of methyl paraoxon obtained under acidic conditions were in the range of 10 to 21mg L-1 d-1, which is remarkable since most similar biocatalysts are active under alkaline conditions. Penicillium chrysogenum activity was outstanding, and it was selected to prepare, characterize, and study the applications of its enzymatic extract. It was used to evaluate the bioremediation of apple surfaces at pH 2 in the presence of SDS, achieving complete methyl paraoxon degradation under proposed conditions. These results indicate that this biocatalyst could complement industrialized fruit washing processes for the elimination of organophosphorus pesticides.

Biophysical Characterization of Autochthonous and New Apple Cultivar Surfaces

Apples have long been known for their beneficial effects on human health due to the presence of various bioactive compounds. It is therefore very important to understand the biophysical properties of apple cuticle that dictate apples’ storability and quality. The purpose of this work was to determine the roughness, hydrophobicity, surface potential, and color of various autochthonous and new apple cultivars. The surface roughness was measured by optical profilometer, hydrophobicity by tensiometer, zeta potential by electro kinetic analyser, and surface color by chroma meter. Measurements reveal that the new cultivar Elstar has the roughest surface while the autochthonous cultivar Crown Prince Rudolph has the lowest roughness. Under normal physiological conditions, all apple surfaces were negatively charged, with Wax apple having the lowest and Crown Prince Rudolph the highest values; most cultivars had an isoelectric point at around pH = 3. The surfaces of the new cultivars were slightly more hydrophobic than those of the autochthonous. We conclude that autochthonous and new apple cultivars differ in biophysical surface properties, which might impact transpiration, bacterial/fungi adhesion and, consequently, apple storage and shelf life potential.

SERS Hotspot Engineering by Aerosol Self‐Assembly of Plasmonic Ag Nanoaggregates with Tunable Interparticle Distance (Adv. Sci. 22/2022)

Pesticide Residue Detection In article number 2201133 by Georgios A. Sotiriou and co-workers, flame aerosol technology is used for the rapid self-assembly of uniform surface-enhanced Raman scattering (SERS) sensing films. These robust nano-sensors can detect pesticide residues on apple surface in a short time of 5 minutes without destroying the fruit, offering a proof-of concept practical application in food-safety diagnostics.

SARS-CoV-2 pseudotyped virus persists on the surface of multiple produce but can be inactivated with gaseous ozone

Due to the immense societal and economic impact that the COVID-19 pandemic has caused, limiting the spread of SARS-CoV-2 is one of the most important priorities at this time. The global interconnectedness of the food industry makes it one of the biggest concerns for SARS-CoV-2 outbreaks. Although fomites are currently considered a low-risk route of transmission for SARS-CoV-2, new variants of the virus can potentially alter the transmission dynamics. In this study, we compared the survival rate of pseudotyped SARS-CoV-2 on plastic with some commonly used food samples (i.e., apple, strawberry, grapes, tomato, cucumber, lettuce, parsley, Brazil nut, almond, cashew, and hazelnut). The porosity level and the chemical composition of different food products affect the virus's stability and infectivity. Our results showed that tomato, cucumber, and apple offer a higher survival rate for the pseudotyped viruses. Next, we explored the effectiveness of ozone in deactivating the SARS-CoV-2 pseudotyped virus on the surface of tomato, cucumber, and apple. We found that the virus was effectively inactivated after being exposed to 15 ppm of ozone for 1 h under ambient conditions. SEM imaging revealed that while ozone exposure altered the wax layer on the surface of produce, it did not seem to damage the cells and their biological structures. The results of our study indicate that ozonated air can likely provide a convenient method of effectively disinfecting bulk food shipments that may harbour the SARS-CoV-2 virus.

Multi-Band-Image Based Detection of Apple Surface Defect Using Machine Vision and Deep Learning

Accurate surface defect extraction of apples is critical for their quality inspection and marketing purposes. Using multi-band images, this study proposes a detection method for apple surface defects with a combination of machine vision and deep learning. Five single bands, 460, 522, 660, 762, and 842 nm, were selected within the visible and near-infrared. By using a near-infrared industrial camera with optical filters, five single-band images of an apple could be obtained. To achieve higher accuracy of defect extraction, an improved U-Net was designed based on the original U-Net network structure. More specially, the partial original convolutions were replaced by dilated convolutions with different dilated rates, and an attention mechanism was added. The loss function was also redesigned during the training process. Then the traditional algorithm, the trained U-Net and the trained improved U-Net were used to extract defects of apples in the test set. Following that, the performances of the three methods were compared with that of the manual extraction. The results show that the near-infrared band is better than the visible band for defects with insignificant features. Additionally, the improved U-Net is better than the U-Net and the traditional algorithm for small defects and defects with irregular edges. On the test set, for single-band images at 762 nm, the improved U-Net had the best defect extraction with an mIoU (mean intersection over union) and mF1-score of 91% and 95%, respectively.

An anti-scratch flexible SERS substrate for pesticide residue detection on the surface of fruits and vegetables

We propose an anti-scratch flexible surface-enhanced Raman scattering substrate with arrayed nanocavity microstructures fabricated by colloidal lithography. The nanocavity microstructure of the substrate can well protect the inner gold nanoparticles during wipe sampling. The prepared flexible substrate was able to detect 4-aminothiophenol (4-ATP) with a concentration down to 1 fM. Furthermore, the substrate was used to detect 6-BA residues on the surface of apples and bean sprouts through wipe sampling, which shows great potential in the field of rapid on-site detection, especially in the detection of pesticide residues on the surface of fruits and vegetables.

Strength of Salmonella attachment on apple and tomato surfaces: Effect of antimicrobial treatments on population reduction and inactivation

Presence of bacteria and its survival on produce surfaces is important in developing non-thermal processing interventions for food safety. In this study, whole apples and tomatoes were individually inoculated with Salmonella bacteria at 4.6 log CFU/g and 3.0 log CFU/g, respectively and then allowed to air dry in a laminar flow biological hood (NuareTM, Plymouth, MN, USA) before antimicrobial treatments at 0, 20 min, 30 min, 60min, 120 min, 360 min, 540 min and 1440 min post inoculation, respectively. After washing treatments, strength of attachment for Salmonella bacteria on apple and tomato surfaces was calculated. The efficacy of a new antimicrobial solution developed in our laboratory, was compared to 1.5% hydrogen peroxide and 200 ppm chlorine treatments. The relative strength of Salmonella attached on whole apples and tomatoes averaged 0.22 and 0.25, respectively. The 200-ppm chlorine and 1.5% hydrogen peroxide (H 2 O2) treatments achieved 2.8 log CFU/g inactivation, while the new antimicrobial solution led to 3.9 log CFU/g and 2.9 log CFU/g reductions on tomatoes and apple surfaces, respectively. Strength of bacterial attachment increased at 360 min post inoculation. The attachment phenomena impacted the activity of all antimicrobial treatments in reducing bacterial populations, except the organic acid solution.

A Novel Organophosphorus Acid Anhydrolase from Deep Sea Sediment with High Degradation Efficiency for Organophosphorus Pesticides and Nerve Agent.

Organophosphorus compounds (OPCs), including highly toxic nerve agents and pesticides, have been used widely in agricultural and military applications. However, they have aroused widespread concern because they persistently pollute the environment and threaten human life. Organophosphorus acid anhydrolase (OPAA) is a promising enzyme that can detoxify OPCs. Here, a novel OPAA (OPAA114644) was isolated and characterized from deep-sea sediment (−3104 m). It exhibited excellent alkaline stability, and the loss of activity was less than 20% in the pH range 5.0–9.0, even after being incubated for 30 d at 4 °C. It also exhibited high salt tolerance, and its enzymatic activity increased by approximately fourfold in the presence of 20% NaCl (w/v). Additionally, OPAA114644 exhibited high degradation efficiency for soman, dichlorvos, paraoxon, coumaphos, and chlorpyrifos with a concentration of up to 250 mg/L, with the degradation rate being 100%, 100%, 100%, 80% and 51%, respectively, in 20 min under optimal conditions. Notably, OPAA114644 dissolved in different solutions, such as 20% NaCl, 1 mM SDS, 0.05% soap, 10% methanol, and tap water, could efficiently decontaminate the residual paraoxon on the surfaces of glasses, cotton tissues, and apples. These results indicate that OPAA114644 has excellent potential for the biodegradation and bioremediation of OPCs pollution and represents a real application of OPAA in the decontamination and detoxification of foods and clothes, and in the remediation of sites such as floors. Deep-sea sediment might also be an abundant resource for various functional microorganisms and enzymes.

Rational Design Yields Molecular Insights on Leaf-Binding of Anchor Peptides.

In times of a constantly growing world population and increasing demand for food, sustainable agriculture is crucial. The rainfastness of plant protection agents is of pivotal importance to reduce the amount of applied nutrients, herbicides, and fungicides. As a result of protective agent wash-off, plant protection is lost, and soils and groundwater are severely polluted. To date, rainfastness of plant protection products has been achieved by adding polymeric adjuvants to the agrochemicals. However, polymeric adjuvants will be regarded as microplastics in the future, and environmentally friendly alternatives are needed. Anchor peptides (APs) are promising biobased and biodegradable adhesion promoters. Although the adhesion of anchor peptides to artificial surfaces, such as polymers, has already been investigated in theory and experimentally, exploiting the adhesion to biological surfaces remains challenging. The complex nature and composition of biological surfaces such as plant leaves and fruit surfaces complicate the generation of accurate models. Here, we present the first detailed three-layered atomistic model of the surface of apple leaves and use it to compute free energy profiles of the adhesion and desorption of APs to and from that surface. Our model is validated by a novel fluorescence-based microtiter plate (MTP) assay that mimics these complex processes and allows for quantifying them. For the AP Macaque Histatin, we demonstrate that aromatic and positively charged amino acids are essential for binding to the waxy apple leaf surface. The established protocols should generally be applicable for tailoring the binding properties of APs to biological interfaces.

Detection of thiram on fruit surfaces and in juices with minimum sample pretreatment via a bendable and reusable substrate for surface-enhanced Raman scattering.

Surface-enhanced Raman scattering (SERS) substrates based on metallic nanoparticles locked in some flexible materials have great potential for rapid detection of pesticide residues in foods, but these substrates are generally not reusable. A bendable and reusable sponge based on polydimethylsiloxane (PDMS) and Au nanospheres was synthesized and employed as SERS substrate to analyze thiram on the surfaces of apples and grapes (20-1000 ng cm-2 ) and in their juices (0.5-5.0mg L-1 ) with minimum sample pretreatments. The lowest detectible concentrations for thiram in fruit juices and on fruit skins were 0.5mg L-1 and 20 ng cm-2 , respectively. The Au-PDMS substrate had acceptable intra-reproducibility for SERS analysis of thiram in fruit juices and on fruit skins, resulting in 3.6-16.9% relative standard deviation (RSD) for the SERS signal of the primary peak of thiram. Moreover, the Au-PDMS substrate exhibited distinguished reusability and stability, which could provide a reproducible SERS signal of thiram in apple juice even after the substrate being reused ten times (RSDs for the three major characteristic peaks of thiram were 2.7-10.5% during the ten reused cycles). This flexible and reusable Au-PDMS SERS substrate for thiram detection could be readily extended to the analysis of other trace chemicals in a broad range of foods, providing a new possibility for SERS application. © 2022 Society of Chemical Industry.

Microlocal properties of seven-dimensional lemon and apple Radon transforms with applications in Compton scattering tomography

We present a microlocal analysis of two novel Radon transforms of interest in Compton scattering tomography, which map compactly supported L 2 functions to their integrals over seven-dimensional sets of apple and lemon surfaces. Specifically, we show that the apple and lemon transforms are elliptic Fourier integral operators, which satisfy the Bolker condition. After an analysis of the full seven-dimensional case, we focus our attention on nD subsets of apple and lemon surfaces with fixed central axis, where n < 7. Such subsets of surface integrals have applications in airport baggage and security screening. When the data dimensionality is restricted, the apple transform is shown to violate the Bolker condition, and there are artifacts which occur on apple–cylinder intersections. The lemon transform is shown to satisfy the Bolker condition, when the support of the function is restricted to the strip .

Quantitative SERS sensing mediated by internal standard Raman signal from silica nanoparticles in flexible polymer matrix

Attributed to poor signal uniformity and external interference, ultrasensitive surface-enhanced Raman spectroscopy (SERS) still faces difficulties in the reliable and quantitative detection of trace molecules. Here, a facile Ag/Si/sodium carboxy methyl cellulose (NaCMC) film with internal standard (IS) was promoted for quantitative determination of thiram. The effects of preparation conditions on SERS activity of the film were systematically investigated and then a flexible SERS substrate with high sensitivity and uniformity was fabricated. The enhancement factor was calculated to be 1.12 × 106 and SERS mapping was recorded with a relative standard deviation value of 19.8% by utilizing 4-mercaptobenzoic acid (4-MBA) as target molecule. Additionally, the dominant contribution of the IS from encapsulated Si nanoparticles (NPs) was confirmed in the quantitative assay of 4-MBA and thiram, facilitating attractive fitting coefficients (R2) as 0.991 and 0.998. Besides that, the proposed flexible film was conducted to scrub trace thiram from the surfaces of apple, orange, and cucumber, resulting in recoveries of 89%, 94%, and 91%. A smart and facile quantitative SERS substrate was developed here for monitoring trace biochemical molecules, verifying its potential utilizations in monitoring pesticide residues.

Apple appearance quality classification method based on double branch feature fusion network

This paper carried out a classification study on the quality of different types of apples. In order to achieve a high-precision classification of high-quality apples in various dimensions, shorten the classification time, improve efficiency, and make it feasible for practical applications. This paper proposes an automatic recognition and classification model OB-Net (for apple appearance quality) based on a dual-branch structure. The model consists of two branches, an O branch and a B branch. The O branch extracts the shape and contour features of the apple surface defect by decomposing the feature map into high and low frequencies. The B branch extracts the shape size and texture characteristics of the apple surface defect by fusing channel attention and spatial attention mechanisms; this is done to further increase the feature distance between different types of defects. Experimental results show that the classification accuracy rates of rot, insect bites, russeting, scratches, and intact apples are 95.65%, 98.17%, 94.62%, 92.02% and 97.67%, respectively; the overall classification and recognition accuracy rate reaches 95.64%. Finally, the three aspects of the feature map, heat map and category probability statistics map extracted from the OB-Net network model prove the validity of the network model in the classification of apple appearance quality.