Harvest and postharvest factors affecting bruise damage of fresh fruits

CITATION: Hussein, Z., Fawole, O. A. & Opara, U. L. 2020. Harvest and Postharvest Factors Affecting Bruise Damage of Fresh Fruits. Horticultural Plant Journal, 6(1):1-13, doi:10.1016/j.hpj.2019.07.006.The original publication is available at https://www.sciencedirect.com/journal/horticultural-plant-journalFresh fruits are susceptible to bruising, a common type of mechanical damage during harvest and at all stages of postharvest handling. In quest of developing and adoption of strategies to reduce bruise damage, it is of utmost importance to understand major factors influencing bruise susceptibility of fresh produce at these stages. This review presents a critical discussion of factors affecting bruising during harvest and postharvest handling of fresh fruits. Excessive compression forces during harvesting by handpicking or machines, and a series of impacts during harvesting, transport and packhouse operations can cause severe bruise damage. The review has further revealed that bruising is dependent on a number of other factors such as produce maturity, ripening, harvest time (during the day or season) and time lapse after harvest. The susceptibility to bruising is partly dependent on how these factors alter the produce physiological and biochemical properties, and the environmental conditions such as temperature, humidity and several other postharvest treatments. Hence, the successful applications of harvesting techniques by use of trained personnel and proper harvesting equipment are essential to reduce both the incidence and severity of bruising. Furthermore, the careful selection of postharvest handling temperature and other treatments can increase resistance of fresh produce to bruise damage.https://www.sciencedirect.com/science/article/pii/S2468014119301943#:~:text=This%20review%20presents%20a%20critical,can%20cause%20severe%20bruise%20damage.Publishers versio

Effect of drying on the bioactive compounds, antioxidant, antibacterial and antityrosinase activities of pomegranate peel

CITATION: Mphahlele, R. R., et al. 2016. Effect of drying on the bioactive compounds, antioxidant, antibacterial and antityrosinase activities of pomegranate peel. BMC Complementary and Alternative Medicine, 16(1): 143, doi: 10.1186/s12906-016-1132-y.The original publication is available at http://bmcmusculoskeletdisord.biomedcentral.comPublication of this article was funded by the Stellenbosch University Open Access Fund.The use of pomegranate peel is highly associated with its rich phenolic concentration. Series of drying methods are recommended since bioactive compounds are highly sensitive to thermal degradation. The study was conducted to evaluate the effects of drying on the bioactive compounds, antioxidant as well as antibacterial and antityrosinase activities of pomegranate peel. Methods Dried pomegranate peels with the initial moisture content of 70.30 % wet basis were prepared by freeze and oven drying at 40, 50 and 60 °C. Difference in CIE-LAB, chroma (C*) and hue angle (h°) were determined using colorimeter. Individual polyphenol retention was determined using LC-MS and LC-MSE while total phenolics concentration (TPC), total flavonoid concentration (TFC), total tannins concentration (TTC) and vitamin C concentration were measured using colorimetric methods. The antioxidant activity was measured by radical scavenging activity (RSA) and ferric reducing antioxidant power (FRAP). Furthermore, the antibacterial activity of methanolic peel extracts were tested on Gram negative (Escherichia coli and Klebsiella pneumonia) and Gram positive bacteria (Staphylococcus aureus and Bacillus subtilis) using the in vitro microdilution assays. Tyrosinase enzyme inhibition was investigated against monophenolase (tyrosine) and diphenolase (DOPA), with arbutin as positive controls. Results Oven drying at 60 °C resulted in high punicalin concentration (888.04 ± 141.03 mg CE/kg dried matter) along with poor red coloration (high hue angle). Freeze dried peel contained higher catechin concentration (674.51 mg/kg drying matter) + catechin and –epicatechin (70.56 mg/kg drying matter) compared to oven dried peel. Furthermore, freeze dried peel had the highest total phenolic, tannin and flavonoid concentrations compared to oven dried peel over the temperature range studied. High concentration of vitamin C (31.19 μg AAE/g dried matter) was observed in the oven dried (40 °C) pomegranate peel. Drying at 50 °C showed the highest inhibitory activity with the MIC values of 0.10 mg/ml against Gram positive (Staphylococcus aureus and Bacillus subtili. Likewise, the extracts dried at 50 °C showed potent inhibitory activity concentration (22.95 mg/ml) against monophenolase. Principal component analysis showed that the peel colour characteristics and bioactive compounds isolated the investigated drying method. Conclusions The freeze and oven dried peel extracts exhibited a significant antibacterial and antioxidant activities. The freeze drying method had higher total phenolic, tannin and flavonoid concentration therefore can be explored as a feasible method for processing pomegranate peel to ensure retention of the maximum amount of their naturally occurring bioactive compounds.http://bmccomplementalternmed.biomedcentral.com/articles/10.1186/s12906-016-1132-yPublisher's versio

Classification of ‘Granny Smith’ apples with different levels of superficial scald severity based on targeted metabolites and discriminant analysis

To study the metabolic changes in ‘Granny Smith’ apples with different severities of superficial scald, fruit were stored in normal refrigerated air (0°C, 95% RH) for 12 weeks followed by 7 d shelf-life under room conditions (20°C, 65% RH). Fruit were graded to five groups based on scald severity and analysed for ethylene, α-farnesene and 6-methyl-5-hepten-2-one (MHO) levels. Reactive oxygen species (ROS) were measured by confocal laser-scanning microscopy on apple peel treated with fluorescent probe 2’,7’-dichlorodihydrofluorescein diacetate. Ethylene production rate, α-farnesene and MHO contents and ROS intensity increased with increasing scald severity but declined in severely scalded fruit. Malondialdehyde (MDA) concentration in fruit peel, a measure of membrane damage, increased linearly (R=0.891) with increase in scald severity. Discriminant analysis was used to classify fruit by scald severity on the basis of metabolites accumulated. The stepwise model indicated that three attributes (ROS, ethylene production and MDA) contributed significantly (R2≥0.5) to the separation of the five scald severity indexes, with ROS having the highest contribution (partial R² =0.961; p<0.0001), followed by ethylene (R2=0.718; p<0.0001) and MDA (R2=0.578; p<0.0001).

Applications of cytokinins in horticultural fruit crops : trends and future prospects

CITATION: Aremu, Adeyemi O. et al. 2020. Applications of cytokinins in horticultural fruit crops : trends and future prospects. Biomolecules, 10(9):1222, doi:10.3390/biom10091222.The original publication is available at: https://mdpi-res.comCytokinins (CKs) are a chemically diverse class of plant growth regulators, exhibiting wide-ranging actions on plant growth and development, hence their exploitation in agriculture for crop improvement and management. Their coordinated regulatory effects and cross-talk interactions with other phytohormones and signaling networks are highly sophisticated, eliciting and controlling varied biological processes at the cellular to organismal levels. In this review, we briefly introduce the mode of action and general molecular biological effects of naturally occurring CKs before highlighting the great variability in the response of fruit crops to CK-based innovations. We present a comprehensive compilation of research linked to the application of CKs in non-model crop species in different phases of fruit production and management. By doing so, it is clear that the effects of CKs on fruit set, development, maturation, and ripening are not necessarily generic, even for cultivars within the same species, illustrating the magnitude of yet unknown intricate biochemical and genetic mechanisms regulating these processes in different fruit crops. Current approaches using genomic-to-metabolomic analysis are providing new insights into the in planta mechanisms of CKs, pinpointing the underlying CK-derived actions that may serve as potential targets for improving crop-specific traits and the development of new solutions for the preharvest and postharvest management of fruit crops. Where information is available, CK molecular biology is discussed in the context of its present and future implications in the applications of CKs to fruits of horticultural significance.Publisher's versio

Chitosan-Bidens pilosa Extract-Based Coating with Enhanced Free Radical Scavenging, Antifungal, and Water Barrier Properties: Metabolite Profiling, Film Characterization, and Raspberry Preservation

Chitosan (Ch) was functionalized with Bidens pilosa (BP) extract at 1, 3, or 5% to form Ch-1 BP, Ch-3 BP, and Ch-5 BP, respectively. Ch without plant extract was used as a control. The composite films were characterized and tested for antifungal properties in the agar disc diffusion approach and antioxidant capacity in the 2,2-diphenyl-1-picrylhydrazyl assay. Chitosan films fused with B. pilosa extract inhibited the growth of P. expansum with a 10 mm inhibition diameter compared to control films (3.33 mm). Ch-1 BP exhibited the highest (79.13%) radical scavenging activity (RSA), and control films had the lowest RSA (50.97%). Liquid chromatography-mass spectrometry analysis identified 20 metabolites, including phenolic acids (9), organic acids (8), monosaccharides (1), amino acids (1), flavonoids (1), and six unknown polyphenols. Chitosan-based composite coating (Ch-1% BP) exhibited the lowest weight loss percentage (16.74%) and decay incidence (17.3%), while the untreated fruit showed higher weight loss and decay incidence (48.33% and 83.2%, respectively). The effectiveness of chitosan-enriched coating in maintaining the postharvest quality of raspberry fruit suggests that this plant could be a postharvest agent for controlling microbial spoilage and protecting against oxidative stress, ultimately resulting in extended storage in horticultural crops

Green synthesized nanomaterials as an alternative to restricted chemicals in postharvest preservation of horticultural crops: a review

Synthetic chemicals have been successfully used to control economic postharvest pathogens such as Botrytis cinerea, Penicillium spp., Rhizopus spp., etc., thus reducing postharvest losses. However, their active ingredient and co-formulants have resulted in their use being restricted internationally due to health concerns and consumers’ requests for safe and natural alternatives. As an alternative to chemicals, green synthesized nanomaterials incorporated with edible coatings in a polymer matrix have been successfully applied on horticultural crops to improve their shelf-life Due to their known antimicrobial activities, plant extracts and nanoparticles such as silver and zinc oxide have been successfully used in food processing applications. Green sources are used as stabilizer and reducing agents to synthesize shape and sizecontrolled metal and metal oxide nanoparticles. Thus, eco-friendly nanoparticles are produced without using toxic materials and are cost-effective. Edible coatings form a thin layer that prevents oxidation, maintains the product quality, can be safely eaten as part of the product, and does not add unfavourable properties. Studies showed that edible coatings with or without green nanomaterials have been successfully used to control postharvest losses and improve the shelf-life of fruit crops such as plums, raspberries, etc

Optimisation Using Response Surface Methodology of Quality, Nutritional and Antioxidant Attributes of ‘Wichita’ Pecan Nuts Roasted by Microwaves

Pecan (Carya illinoinensis) nuts are rich in functional compounds (unsaturated fatty acids, phytosterols, polyphenols, and tocopherols) associated with various health benefits. Commercially, pecan nuts are roasted to enhance their physical, chemical, and sensory properties. In the present study, response surface methodology (RSM) was used to optimise the quality and nutritional and antioxidant attributes of ‘Wichita’ pecan nuts roasted by using a microwave process with a range of microwave power (96.45–803.55 W) and roasting time (1.37–5.62 min). The microwave-roasted pecan nuts were analysed for hardness, total colour difference (TCD), and radical scavenging activity and modelled using the central composite design. The results showed that microwave power and roasting time significantly (p p < 0.05) by microwave roasting the pecan nuts at determined conditions. Volatile compounds, such as alcohols, aldehydes, ketones, lactones, hydrocarbons, and carboxylic acids, were identified in both raw and microwave-roasted pecan nuts, with limonene, which possesses various health properties, being the major volatile compound. It can be concluded that microwave roasting may be optimised using response surface methodology to produce quality pecan nuts that can be used as snacks or as an ingredient in other snack products

Chemical and phytochemical properties and antioxidant activities of three pomegranate cultivars grown in South Africa

The original publication is available at http://www.springerlink.comA comparative study of chemical contents and antioxidant activities of three pomegranate cultivars (‘Arakta’, ‘Bhagwa’ and ‘Ruby’) grown in South Africa was conducted. Fresh pomegranate juice (PJ) of each cultivar were assessed for soluble solid contents (SSCs), pH and titratable acidity (TA), while extracted juice samples were evaluated for total phenolic (TP), including total tannins (TT), proanthocyanidins (Pcy), total flavonoids, anthocyanins and gallic acids (GA) using spectrophotometric methods. The antioxidant properties of the juice samples were evaluated against stable 2, 2– diphenyl–1–picryl hydrazyl, as well as in ferric reducing ability of plasma (FRAP) and QuantiChrom™ (TAC) antioxidant assays. There were significant differences in the chemical properties of the cultivars. SSC, TA and pH varied between the range of 14.07–15.10 °Brix, 0.22– 0.28 g/100 ml and 3.32–3.64, respectively. ‘Bhagwa’ had the highest TP (449.9 mg/100 ml), 1.3-fold and 1.6-fold higher than ‘Arakta’ and ‘Ruby’, respectively. The strongest total antioxidant activity was exhibited by ‘Bhagwa’ with an antioxidant index of 95.7%, followed by ‘Arakta’ (93.2%) and ‘Ruby’ (79.9%). PJ phytochemical properties (TP, TT, Pcy, GA) and antioxidant activity (FRAP and TAC) were significantly correlated (r2= 0.509–0.885) with each other.Publishers' Versio

Antibacterial, antioxidant and tyrosinase-inhibition activities of pomegranate fruit peel methanolic extract

The original publication is available at http://www.biomedcentral.com/1472-6882/12/200Publication of this article was funded by the Stellenbosch University Open Access Fund.Abstract Background This study evaluated, using in vitro assays, the antibacterial, antioxidant, and tyrosinase-inhibition activities of methanolic extracts from peels of seven commercially grown pomegranate cultivars. Methods Antibacterial activity was tested on Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Klebsiella pneumonia) using a microdilution method. Several potential antioxidant activities, including radical-scavenging ability (RSA), ferrous ion chelating (FIC) and ferric ion reducing antioxidant power (FRAP), were evaluated. Tyrosinase enzyme inhibition was investigated against monophenolase (tyrosine) and diphenolase (DOPA), with arbutin and kojic acid as positive controls. Furthermore, phenolic contents including total flavonoid content (TFC), gallotannin content (GTC) and total anthocyanin content (TAC) were determined using colourimetric methods. HPLC-ESI/MSn analysis of phenolic composition of methanolic extracts was also performed. Results Methanolic peel extracts showed strong broad-spectrum activity against Gram-positive and Gram-negative bacteria, with the minimum inhibitory concentrations (MIC) ranging from 0.2 to 0.78 mg/ml. At the highest concentration tested (1000 &#956;g/ml), radical scavenging activities were significantly higher in Arakta (83.54%), Ganesh (83.56%), and Ruby (83.34%) cultivars (P&lt; 0.05). Dose dependent FIC and FRAP activities were exhibited by all the peel extracts. All extracts also exhibited high inhibition (&gt;50%) against monophenolase and diphenolase activities at the highest screening concentration. The most active peel extract was the Bhagwa cultivar against monophenolase and the Arakta cultivar against diphenolase with IC50 values of 3.66 &#956;g/ml and 15.88 &#956;g/ml, respectively. High amounts of phenolic compounds were found in peel extracts with the highest and lowest total phenolic contents of 295.5 (Ganesh) and 179.3 mg/g dry extract (Molla de Elche), respectively. Catechin, epicatechin, ellagic acid and gallic acid were found in all cultivars, of which ellagic acid was the most abundant comprising of more than 50% of total phenolic compounds detected in each cultivar. Conclusions The present study showed that the tested pomegranate peels exhibited strong antibacterial, antioxidant and tyrosinase-inhibition activities. These results suggest that pomegranate fruit peel could be exploited as a potential source of natural antimicrobial and antioxidant agents as well as tyrosinase inhibitors.Publishers' Versio

Characterization of banana powder-based film reinforced with CNF and Bio-mediated ZnO nanoparticles for potential food applications

The formulation of a multifunctional nanocomposite packaging material with potential against agents of food deterioration, such as free radicals and microorganisms, has emerged as a solution for shelf-life extension and food security. This study developed banana powder (BP) film infused with cellulose nanofiber (CNF) and ZnO-PPW and ZnO-PSW nanoparticles (NPs) at different concentrations for food applications. The BP/CNF/ZnO films were characterized using UV–vis spectroscopy, XRD, FT-IR, and SEM techniques. The analyses confirmed the successful infusion of ZnO NPs into the BP/CNF matrix, leading to significant changes (p < 0.05) in color and appearance, enhanced UV–vis barrier properties, and increased thickness and flexibility of the films. Furthermore, the presence of ZnO in the base matrix influenced the moisture content (19%–29%), film solubility (68%–74%), and oil permeability significantly more than the control BP/CNF film. Adding ZnO significantly improved the UV barrier properties compared to the control. The nanocomposite BP/CNF/ZnO films demonstrated concentration-based antioxidant and good antimicrobial activity against five selected food pathogens ( Escherichia coli , Enterococcus faecalis, Listeria monocytogenes and Staphylococcus aureus ). Similarly, good antioxidant properties were reported in different assays, proving superior to the control BP/CNF. These key findings, especially those of the BP/CNF/ + 0.6% ZnO NPs films, showed that these films possess great potential for application as food packaging materials with antioxidant and antimicrobial properties