Internal quality prediction technology for 'Sulhyang' strawberry fruit using organic analysis and hyperspectral imaging.

In recent years, hyperspectral imaging combined with machine learning techniques has garnered significant attention for its potential in assessing fruit maturity. This study proposes a method for predicting strawberry fruit maturity based on the harvest time. The main features of this study are as follows. 1) Selection of wavelength band associated with strawberry growth season; 2) Extraction of efficient parameters to predict strawberry maturity 3) Prediction of internal quality attributes of strawberries using extracted parameters. In this study, experts cultivated strawberries in a controlled environment and performed hyperspectral measurements and organic analyses on the fruit with minimal time delay to facilitate accurate modeling. Data augmentation techniques through cross-validation and interpolation were effective in improving model performance. The four parameters included in the model and the cumulative value of the model were available for quality prediction as additional parameters. Among these five parameter candidates, two parameters with linearity were finally identified. The predictive outcomes for firmness, soluble solids content, acidity, and anthocyanin levels in strawberry fruit, based on the two identified parameters, are as follows: The first parameter, ps, demonstrated RMSE performances of 1.0 N, 2.3 %, 0.1 %, and 2.0 mg per 100 g fresh fruit for firmness, soluble solids content, acidity, and anthocyanin, respectively. The second parameter, p3, showed RMSE performances of 0.6 N, 1.2 %, 0.1 %, and 1.8 mg per 100 g fresh fruit, respectively. The proposed non-destructive analysis method shows the potential to overcome the challenges associated with destructive testing methods for assessing certain internal qualities of strawberry fruit.

Development of multifunctional chitosan-based composite film loaded with tea polyphenol nanoparticles for strawberry preservation.

Incorporating polysaccharide-based composite films with nanobiotechnology offers a new strategy for food preservation. This study initially focuses on the preparation of tea polyphenol nanoparticles (TPNP), novel and derived from natural antibacterial agents, which serve to improve stability. Afterwards chitosan-based composite films loaded with TPNP (CTN film) were developed using solution casting method. The incorporation of TPNP significantly improved the UV/water/oxygen barrier properties, mechanical properties and thermal stability, alongside notable physical properties including water contact angle (93.65 ± 0.04°), low water vapor permeability (33.72 ± 3.32 g/m2h) and oxygen permeability (0.11 ± 0.02 g/m2h), tensile strength (61.83 ± 0.70 %), and elongation at break (31.60 ± 6.12 %). The CTN film not only exhibited exceptional biodegradability and nontoxicity, but also demonstrated remarkable antimicrobial efficacy against Escherichia coli and Bacillus subtilis. Additionally, it showcased potent antioxidant activity, boasting DPPH and ABTS radical scavenging rates up to 89.25 ± 0.18 % and 93.84 ± 0.42 %. The CTN film was successfully formed on the surface of strawberries through dip-coating process and their shelf life was extended from 4 to 6 days at 20 °C without side-effect on the weight loss, harness, pH and total soluble solids, illustrating its potential for enhancing food preservation.

Screening of optimal cleaning methods to reduce microplastic residues on strawberry surfaces: Characterization of microplastics in strawberry wash water.

Microplastics are widespread in facility strawberry greenhouses and can be deposited on the surface of strawberries through air currents. Investigating effective cleaning methods represents a viable strategy to reduce human ingestion of MPs. Therefore, different cleaning methods were compared: ultrasonic cleaning for 30 min, deionized water rinsing once, deionized water immersion for 30 min, and fruit immersion in washing salt for 30 min. The MPs in strawberry washing water were analyzed and compared using laser direct infrared imaging to investigate their characteristics and the optimal reduction of MPs on the surface of strawberries. The quality of the cleaning results was in the following order: water immersion > washing salt immersion > water rinsing > ultrasound. Water immersion was 1.3-2 times more effective in removing microplastics than other treatments. Furthermore, 21 polymer types were detected in the samples. Most MPs were less than 50 µm in size. The main polymers in this size range were polyamide, chlorinated polyethylene, and polyethylene terephthalate, and they mainly existed as fragments, fibers, and beads. This study provides a valuable reference for reducing human intake of microplastics through fresh fruits and vegetables.

A Novel Preservative Film with a Pleated Surface Structure and Dual Bioactivity Properties for Application in Strawberry Preservation due to Its Efficient Apoptosis of Pathogenic Fungal Cells.

Botrytis cinerea (B. cinerea) and Colletotrichum gloeosporioides (C. gloeosporioides) were isolated from the decaying strawberry tissue. The antifungal properties of Monarda didyma essential oil (MEO) and its nanoemulsion were confirmed, demonstrating complete inhibition of the pathogens at concentrations of 0.45 µL/mL (0.37 mg/mL) and 10 µL/mL, respectively. Thymol, a primary component of MEO, was determined as an antimicrobial agent with IC50 values of 34.51 (B. cinerea) and 53.40 (C. gloeosporioides) µg/mL. Hippophae rhamnoides oil (HEO) was confirmed as a potent antioxidant, leading to the development of a thymol-HEO-chitosan film designed to act as an antistaling agent. The disease index and weight loss rate can be reduced by 90 and 60%, respectively, with nutrients also being well-preserved, offering an innovative approach to preservative development. Studies on the antifungal mechanism revealed that thymol could bind to FKS1 to disrupt the cell wall, causing the collapse of mitochondrial membrane potential and a burst of reactive oxygen species.

The regulation of postharvest strawberry quality mediated by abscisic acid under elevated CO2 stress.

Elevated CO2 was a potential strategy for strawberry preservation. However, the regulatory mechanism remained unclear. In current study, transcriptome analysis showed that elevated CO2 played important roles in regulating strawberry fruit quality at the transcriptional level, and plant hormones metabolism at least partially involved in the regulatory process. Further, ABA was demonstrated to play important roles in the response to elevated CO2. Elevated CO2 inhibited the accumulation of ABA, which was 61% lower than that in control. Elevated CO2 repressed ABA synthesis by inhibiting NCED activity and the expression of FaNCED1/2, leading to the reduction of ABA accumulation as a result. Meanwhile, elevated CO2 also decreased ABA sensitivity by down-regulating FaSnRK2.4/2.6 and FaABI5 expression. The dual down-regulation of ABA signaling accounted for the regulation of fruit quality under elevated CO2 treatment. These results provide new insights into the mechanism of strawberry fruit response to elevated CO2.

Effect of CPPU on optical properties of strawberry in near-infrared range during growth.

To investigate the effect of CPPU (forchlorfenuron) on optical properties of strawberry during growth, the optical properties (absorption coefficient (µa) and reduced scattering coefficient (µs')) of strawberry treated with CPPU solutions at different concentrations (0, 2.5, 5.0 and 7.5 mg/L) were measured in white, color turning and red stages by using a single integrating sphere system over near-infrared wavelength range of 900-1700 nm. The physicochemical properties, i.e., single fruit weight, soluble solids content, firmness and moisture content, as well as microstructure of strawberry were also investigated. The results showed that in white stage, the µa of strawberry treated with 7.5 mg/L CPPU was significantly (p ≤ 0.05) lower than that of untreated strawberry at absorption peak of 1411 nm. In color turning stage, the µs' of strawberry treated with 5 mg/L CPPU was significantly lower than that of treated with 2.5 mg/L at absorption peaks of 975, 1197 and 1411 nm. In red stage, the µa of strawberry treated with 2.5 mg/L CPPU was significantly (p ≤ 0.05) different from that of treated with 7.5 mg/L at 1197 nm. The study indicates that the optical properties of strawberry were affected by CPPU, and it provides useful information for identifying CPPU treated strawberry.

Development and Optimization Method for Determination of the Strawberries' Aroma Profile.

The strawberry (genus Fragaria) is a plant from the rose family (Rosaceae). As the fruits are likely to be picked mechanically, they are grown close to consumption centers. The aim of this work was to develop a suitable method for detecting as many molecules as possible in order to be able to distinguish between different strawberry cultivars and geographical origins in the future. Whole strawberries of the "Albion" cultivar, grown in the Jagodica Purgerica region of Zagreb, were used. Gas chromatography-mass spectrometry (GC-MS) in SCAN mode was used to analyze the aroma profile and to determine the proportion of individual components. The samples were prepared and analyzed using the solid-phase microextraction method (SPME). The impact of SPME fiber selection and GC column type was investigated, as well as sample weight, ionic strength, agitation temperature, and sampling time. A higher ionic strength was achieved by adding a 20% NaCl solution to the sample. The aroma profile of the studied strawberry cultivar consisted of furanone, esters, aldehydes, and carboxylic acids. Optimal results were achieved by adjusting the ionic strength during 15 min of extraction and incubation. The individual compounds were identified using NIST, Wiley libraries, and the "area normalization" method.

Optimizing the Extraction of the Polyphenolic Fraction from Defatted Strawberry Seeds for Tiliroside Isolation Using Accelerated Solvent Extraction Combined with a Box-Behnken Design.

Tiliroside is a natural polyphenolic compound with a wide range of biological activity, and defatted strawberry seeds are its rich source. The goal of this study was to optimize accelerated solvent extraction (ASE) conditions, including temperature, solvent composition, and the number of extraction cycles, using Box-Behnken design to maximize the yield of tiliroside. UPLC-DAD-MS was applied to investigate the polyphenolic composition of the extracts, and preparative liquid chromatography (pLC) was used for isolation. All obtained mathematical models generally showed an increase in the efficiency of isolating polyphenolic compounds with an increase in temperature, ethanol content, and the number of extraction cycles. The optimal established ASE conditions for tiliroside were as follows: a temperature of 65 °C, 63% ethanol in water, and four extraction cycles. This allowed for the obtainment of a tiliroside-rich fraction, and the recovery of isolated tiliroside from plant material reached 243.2 mg from 100 g. Our study showed that ASE ensures the isolation of a tiliroside-rich fraction with high effectiveness. Furthermore, defatted strawberry seeds proved to be a convenient source of tiliroside because the matrix of accompanying components is relatively poor, which facilitates separation.

Preparation, structural analysis of alcohol aroma compounds/ß-cyclodextrin inclusion complexes and the application in strawberry preservation.

The dynamic combination of aromas and cyclodextrins is an important means to achieve their stability and controllability, and accurately revealing their interaction rules is the key to designing and constructing high-quality aroma nanocarriers. In this study, the inclusion mechanism between alcohol aroma compounds with different structures and ß-cyclodextrin (ß-CD) was studied by combining molecular dynamics simulation and experimental methods. Results showed that the selected alcohol aroma compounds formed inclusion complexes (ICs) with ß-CD in a 1:1 ratio, while alcohol aroma compounds containing cyclic structures were more tightly bound to ß-CD. Van der Waals forces were the primary forces driving the formation and stabilization of the ICs. Cinnamyl alcohol/ß-CD ICs showed the most significant antimicrobial effect and notably prolonged the shelf life of strawberries. This study aimed to provide theoretical support for precisely designing and preparing highly stable flavours and fragrances, as well as expanding their application range.

Development and characterization of pectin-based composite film incorporated with cannabidiol/2,6-di-O-methyl-ß-cyclodextrin inclusion complex for food packaging.

To reduce environmental pollution and improve human health, developing green active food packaging materials is very necessary. In this study, a novel antioxidant and antibacterial composite film was produced by incorporating inclusion complex (CDIC) of cannabidiol (CBD) with 2,6-di-O-methyl-ß-cyclodextrin (DM-ß-CD) into pectin. The pectin films loaded with CBD and hemp leaf water extract (HLE) were prepared for comparison. Comprehensive characterizations showed CBD was encapsulated by DM-ß-CD and CDIC was evenly dispersed into pectin matrix, forming the compact and intact film. The composite films showed good mechanical properties and biodegradability. CDIC film showed the highest transparency and smoothness (Rrms/Rmax: 2.6/16.8 nm). The addition of bioactives reduced the water-binding capacity and CDIC film had the strongest hydrophobicity. Besides, DM-ß-CD encapsulation improved the thermal stability of CBD in CDIC film. Benefiting from encapsulation and excellent bioactivities of CBD, CDIC film showed excellent antioxidant capacity and antibacterial activity, effectively inhibiting colony growth and maintaining the strawberry color in strawberry preservation. This work could provide a novel eco-friendly candidate for food packaging material and expand the use of CBD in food industry.

Preparation of citric acid cross-linked chitosan quaternary phosphonium/polyvinyl alcohol composite film and its application in strawberry preservation.

Chitosan quaternary phosphine salts (NPCS) were synthesized with enhanced antimicrobial properties using a two-step method. Composite films (CNSP) were prepared by incorporating NPCS and polyvinyl alcohol (PVA) as the base material, citric acid as the crosslinker and functional additive, exhibiting antibacterial and UV-blocking properties. The composite film showed a maximum tensile strength of 20.4 MPa, an elongation at break of 677%, and a UV light barrier transmittance of 70%. Application of these composite membranes in preserving strawberries demonstrated effectiveness in maintaining freshness by preventing water loss, inhibiting microbial growth, and extending shelf life. In addition, the composite film demonstrated biosafety. These results indicate that CNSP composite films holds significant promise for safe and sustainable food packaging applications.

Full life cycle green preparation of collagen-based food packaging films using Halocynthia roretzi as raw material.

The extraction of collagen for packaging films typically requires a time-consuming process and the use of substantial chemicals. Herein, we present a full life cycle green preparation method for rapidly producing collagen-based food packaging films using Halocynthia roretzi (HR), a collagen-rich marine organism, as raw material. We first prepared the micro/nano-sized collagen fibers from HR tissue by utilizing urea and sonication as effective hydrogen-bond breakers. Subsequently, the collagen fiber was rapidly fabricated into a film through vacuum filtration. The resulting collagen fiber film (CFF) exhibited a uniform and dense surface, along with good tensile properties, water resistance, and biodegradability. In addition, the deposition of chitosan (CS) on the surface of CFF resulted in a remarkable preservation effect for both strawberries and pork. This full life cycle preparation method for collagen-based films provides a promising and innovative approach to the sustainable preparation of food packaging films.

Preparation of the double cross-linking carbon dots-polyvinyl alcohol-carboxymethyl cellulose composite film for food active packaging application.

This paper prepared a new kind of carbon dots-polyvinyl alcohol-carboxymethyl cellulose composite film with antibacterial properties. Carbon dots and citric acid were used as cross-linking agents, and polyvinyl alcohol and carboxymethyl cellulose were used as matrices respectively. The mechanical properties, UV shielding performance, thermal stability, antioxidant capability, and antibacterial activities of the carbon dots-polyvinyl alcohol-carboxymethyl cellulose composite film were researched. The prepared carbon dots-polyvinyl alcohol-carboxymethyl cellulose composite film was applied in the strawberry freshness preservation test. And test results indicated that the carbon dots-polyvinyl alcohol-carboxymethyl cellulose composite film could prevent rotting and extend the shelf life of strawberries. This carbon dots-polyvinyl alcohol-carboxymethyl cellulose composite film could be applied in the food active packaging field.

Development of apple pectin/soy protein isolate-based edible films containing punicalagin for strawberry preservation.

In this study, we developed punicalagin-loaded antimicrobial films based on soy protein isolate (SPI) and apple pectin (AP). The AP was derived from apple pomace waste while the punicalagin was obtained from pomegranate peel. Punicalagin was identified to exist in both α- and ß-isomers, with the ß-type being predominant. The composite films were characterized using scanning electron microscopy, Fourier transformed infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. Our results demonstrated that the incorporation of AP significantly enhanced the mechanical strength, heat resistance, and barrier properties of the films. Moreover, the composite films integrated with punicalagin exhibited excellent antimicrobial activities against Staphylococcus aureus (with a minimum bactericidal concentration value of 0.25 %), Escherichia coli (with a minimum bactericidal concentration value of 0.50 %), and Aspergillus niger. Finally, these antimicrobial film solutions were tested as coatings on strawberries and found to have significantly better effects on reducing weight loss, improving shelf-life, and maintaining the freshness of strawberries compared to coatings without punicalagin. The results indicate that antimicrobial coatings loaded with punicalagin hold great promise as multifunctional active packaging materials for fruit preservation.

Emulsion-based edible chitosan film containing propolis extract to extend the shelf life of strawberries.

In this study, propolis was first loaded into a conventional oil-in-water emulsion, which was combined with a chitosan film-forming solution to produce propolis emulsion-loaded film (PEF). Strawberries inoculated with Botrytis cinerea coated with PEF and blank emulsion-loaded films (BEF) were stored for 14 days at 4 °C. Compared to BEF, PEF showed superior mechanical and oxygen barrier properties, as well as antioxidant activities, but higher moisture permeability. PEF showed less oil agglomeration on the film surface after drying, as demonstrated by scanning electron microscopy (SEM) analysis. Compared to uncoated strawberries, coatings did not have a significant effect on weight loss or firmness during storage. In contrast, coated strawberries showed elevated total phenolics, anthocyanins, and ascorbic acid retention; however, PEF-coating yielded higher values. Moreover, the PEF coating resulted in a significantly lower reduction of organic acid and total soluble solids. Mold growth was visible in both uncoated and BEF-coated strawberries after 7 days of storage, while PEF-coated fruits showed no visible mold until the end of storage. Starting from day 4, PEF-coated fruits showed lower mold counts (~2 log CFU/g) than other samples. Therefore, the PEF prepared in this study has application potential for the preservation of fresh fruits.

Uncovering fruit flavor and genetic diversity across diploid wild Fragaria species via comparative metabolomics profiling.

Wild Fragaria resources exhibit extensive genetic diversity and desirable edible traits, such as high soluble solid content and flavor compounds. However, specific metabolites in different wild strawberry fruits remain unknown. In this study, we characterized 1008 metabolites covering 11 subclasses among 13 wild diploid resources representing eight species, including F. vesca, F. nilgerrensis, F. viridis, F. nubicola, F. pentaphylla, F. mandschurica, F. chinensis, and F. emeiensis. Fifteen potential metabolite biomarkers were identified to distinguish fruit flavors among the 13 diploid wild Fragaria accessions. A total of nine distinct modules were employed to explore key metabolites related to fruit quality through weighted gene co-expression module analysis, with significant enrichment in amino acid biosynthesis pathway. Notably, the identified significantly different key metabolites highlighted the close association of amino acids, sugars, and anthocyanins with flavor formation. These findings offer valuable resources for improving fruit quality through metabolome-assisted breeding.

Eliciting Polyphenols in Strawberry Leaves: Preliminary Experiments in Fragaria × ananassa cv. Festival.

Polyphenols are plant secondary metabolites that function mostly as a general stress-induced protective mechanism. Polyphenols have also gained interest due to their beneficial properties for human health. Strawberry leaves represent an agro-industrial waste material with relevant bioactive polyphenol content, which could be incorporated into circular economy strategies. However, due to the low quantities of polyphenols in plants, their production needs to be improved for cost-effective applications. The objective of this research was to compare polyphenol production in strawberry (Fragaria × ananassa cv. Festival) leaves in plants grown in greenhouse conditions and plants grown in vitro, using three possible elicitor treatments (UV irradiation, cold exposure, and cysteine). General vegetative effects were morphologically evaluated, and specific polyphenolic compounds were quantified by UHPLC-DAD-MS/MS. Gallic acid was the most abundant polyphenol found in the leaves, both in vivo and in vitro. The results showed higher amounts and faster accumulation of polyphenols in the in vitro regenerated plants, highlighting the relevance of in vitro tissue culture strategies for producing compounds such as polyphenols in this species and cultivar.

Strawberries treated with biodegradable film containing plant extracts.

Strawberry (Fragaria x ananassa Duch.) is a highly perishable fruit whose characteristics make it susceptible to developing microorganisms. Plant extracts have been studied as an alternative to pesticides to control spoilage microorganisms, responding to the expectation of the population seeking a healthier way of life. The fungus Botrytis cinerea is a facultative pathogen of vegetables, which can affect all stages of the development of several fruits, such as the strawberry, where it causes gray rot. Trichilia catigua (catuaba), Paullinia cupana (guarana), Stryphnodendron barbatiman (barbatimão), and Caesalpinia peltophoroides (sibipiruna) are planted in the Brazilian flora and have demonstrated pharmacological properties in their extracts. This work aimed to treat strawberries with a biodegradable film containing extracts of these species to evaluate strawberry conservation. There were notable distinctions in mass loss between the extract-treated and control samples. The pH, total acidity (TA), and soluble solids parameters exhibited consistently significant means across both sets of samples. Luminosity increased over the course of days in the color parameters, with the exception of strawberries coated with guarana. The red color showed greater intensity, except for those coated with barbatimão extract. Considering the results, it is possible to conclude that the coatings used can become an alternative to enhance the conservation of strawberries.

Comprehensive Analysis of Physicochemical Properties and Volatile Compounds in Different Strawberry Wines under Various Pre-Treatments.

Pre-fermentation treatment has an important impact on the color, aroma, taste, and other characteristics of fruit wine. To discover suitable pre-treatment techniques and conditions that yield strawberry wine of excellent quality, the influences of juice fermentation, pulp maceration, thermovinification, and enzymatic hydrolysis pre-treatments on the basic chemical composition, color, antioxidant capacity, and volatile organic compounds in strawberry wines were investigated. The results showed that the color, antioxidant properties, and volatile aroma of strawberry wines fermented with juice were different from those with pulp. Strawberry wines fermented from juice after 50 °C maceration had more desirable qualities, such as less methanol content (72.43 ± 2.14 mg/L) compared with pulp-fermented wines (88.16 ± 7.52 mg/L) and enzymatic maceration wines (136.72 ± 11.5 mg/L); higher total phenolic content (21.78%) and total flavonoid content (13.02%); enhanced DPPH (17.36%) and ABTS (27.55%) free radical scavenging activities; richer essential terpenoids and fatty acid ethyl esters, such as linalool (11.28%), ethyl hexanoate (14.41%), ethyl octanoate (17.12%), ethyl decanoate (32.49%), and ethyl 9-decenoate (60.64%); pleasant floral and fruity notes compared with juice-fermented wines macerated at normal temperatures; and a lighter color. Overall, juice thermovinification at 50 °C is a potential pre-treatment technique to enhance the nutrition and aroma of strawberry wine.

Functional properties, structural characteristics, and anti-complementary activities of two degraded polysaccharides from strawberry fruits.

Two low-molecular-weight polysaccharides (DPSP50 and DPSP70) were obtained using hydrogen peroxide-vitamin C (H2O2-Vc) treatment at 50 °C and 70 °C, respectively. Both DPSP50 and DPSP70 comprised the same six monosaccharides in different ratios, and their molecular weights (Mws) were 640 kDa and 346 kDa, respectively. Functional properties analyses demonstrated that DPSP50 and DPSP70 each had an excellent water holding capacity, oil absorption capacity, and emulsion properties, as well as shear-thinning characteristics and viscoelastic properties. Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopic assays confirmed the existence of α-, ß-pyranose rings and the same six sugar residues in DPSP50 and DPSP70. The results of Congo red test, scanning electron microscopy (SEM), and X-ray diffraction (XRD) demonstrated that DPSP50 and DPSP70 did not contain triple-helix conformations, but were amorphous aggregates with flake-like shape and rough surface. Additionally, both DPSP50 and DPSP70 showed strong anti-complementary activities through the classical pathway and the alternative pathway. The results support the potential utility of these degraded polysaccharides from strawberry fruits in functional foods and medicines.