Postharvest UV-C treatment of tomato fruits: Changes in simple sugars and organic acids contents during storage

Enhancing post-harvest quality of sapota using ultraviolet-C irradiation: A study on efficacy and effects

Ultraviolet-C (UV-C) radiation has been identified as a promising method for enhancing the shelf life of fruits and vegetables by reducing microbial count and boosting their defence mechanisms. In this study, the impact of UV-C radiation on the physical, biochemical, and microbial properties of sapota fruits was investigated by subjecting them to different doses (2.5, 5, 7.5, and 10 kJ m-2; 12 ± 1°C; 85-90% relative humidity) to enhance their shelf life. The results revealed that higher doses of UV-C radiation resulted in significantly lower weight loss and higher firmness compared to untreated samples and samples treated with lower doses. Furthermore, UV-C-treated fruits displayed a delayed increase in total soluble solids, total sugar, and reduced sugar content compared to the untreated fruit during storage. The UV-C-treated fruits also exhibited a delayed decline in ascorbic acid and titratable acidity during storage. The treated fruits exhibited significantly higher phenolic content than the untreated fruits. Additionally, significantly lower decay and microbial count were observed in fruits treated with higher doses than in those treated with lower doses. The samples treated with a dose of 7.5 and 10 kJ m-2 had a shelf life of 25 days compared to 14 days for the control fruits.

1-Methylcyclopropene and UV-C Treatment Effect on Storage Quality and Antioxidant Activity of ‘Xiaobai’ Apricot Fruit

The ‘Xiaobai’ apricot fruit is rich in nutrients and is harvested in summer, but the high temperature limits its storage period. To promote commercial quality and extend shelf life, we investigated the effectiveness of Ultraviolet C (UV-C) combined with 1-methylcyclopropene (1-MCP) treatment on ‘Xiaobai’ apricot fruit stored at 4 ± 0.5 °C for 35 days. The results revealed that the combination treatment of 1-MCP and UV-C performed better than either UV-C or 1-MCP alone in fruit quality preservation. The combination treatment could delay the increase in weight loss, ethylene production, and respiration rate; retain the level of soluble solid content, firmness, titratable acid, and ascorbic acid content; promote the total phenolics and flavonoids accumulation; improve antioxidant enzyme activity and relative gene expression, and DPPH scavenging ability; and reduce MDA, H2O2, O2.− production. The combined treatment improved the quality of apricot fruit by delaying ripening and increasing antioxidant capacity. Therefore, combining UV-C and 1-MCP treatment may be an effective way to improve the post-harvest quality and extend the storage period of the ‘Xiaobai’ apricot fruit, which may provide insights into the preservation of ‘Xiaobai’ apricot fruit.

Postharvest Quality of Cherry Tomatoes Coated with Mucilage from Dragon Fruit and Irradiated with UV-C

Cherry tomatoes are climacteric fruits that have a limited shelf life. Over the years, many methods have been applied to preserve the fruit quality and safety of these fruits. In this study, a novel method of combining mucilage from dragon fruits and UV-C irradiation was carried out. Cherry tomatoes were subjected to UV-C irradiation and edible coating, both as a stand-alone and hurdle treatment. The edible coating was prepared from the mucilage of white dragon fruits. Quality parameters including color, weight loss, total soluble solids, titratable acidity, ascorbic acid, antioxidant analysis (total phenolic content and flavonoid content), and microbial analysis were measured throughout 21 days of storage at 4 °C. Results showed that the hurdle treatment extended shelf life by 21 days, reduced weight loss (0.87 ± 0.05%) and color changes (11.61 ± 0.95 ΔE), and inhibited microbes better than stand-alone treatments. Furthermore, fruits treated with the combination of UV-C and edible coating also contained higher total polyphenol content (0.132 ± 0.003 mg GAE/100 mL), total flavonoid content (13.179 ± 0.002 mg CE/100 mL), and ascorbic acid (1.07 ± 0.06 mg/100 mL). These results show that the combination of UV-C and edible coating as a hurdle treatment could be an innovative method to preserve shelf life and quality of fruits.

Characterization and Phylodiversity of Implicated Enteric Bacteria Strains in Retailed Tomato (Lycopersicon esculentum Mill.) Fruits in Southwest Nigeria

BACKGROUND: Tomatoes (Lycopersicon esculentum Mill.) have very huge health-promoting benefits due to high nutritional composition; however, these fruits are potential reservoir of enteric food-borne pathogens causing major public health concerns. AIM: Characterization and phylo-analysis of implicated enteric bacteria strains in retailed Tomato fruits in southwest Nigeria were studied. METHODS: Ready to be retailed fresh tomato fruits were purchased from common food markets in southwest, Nigeria, which lies between latitudes 6° 21′ to 8° 30′ N and longitudes 2° 30′ to 5° 30′ E. Observation of sample storage potentials at different conditions and bio-typing of associated bacterial strains were carried out for consecutive 14 days. Enteric bacteria strains were genotyped with 16S rRNA assay and further profiled for antibiotic susceptibility to common antibiotics. High population rate frequently consume tomatoes. RESULTS: Early spoilage characterized with yellow fluid, fungal growth and visible lesions were observed at 25°C storage compare to few patches of lesion at 4°C after 14 days. Higher bacterial count of 4.0–7.18 Log CFU/g was recorded at ambient storage compare to refrigerated samples with more than 10% occurrence rate of Citrobacter spp., Klebsiella spp. and Enterobacter spp. Identified Citrobacter spp. and Klebsiella spp. showed 100% resistant to beta-lactam antibiotics (ceftazidime, cefuroxime, cefixime, ciprofloxacin, and amoxicillin-clavulanic acid). Two-resistant enteric bacteria strains, Klebsiella aerogenes B18 and Citrobacter freundii B27 obtained from Nigerian tomato clustered with Citrobacter strains in food (China), water strains (India, Poland, Malaysia), milk (Germany), and human fecal (China). CONCLUSION: Implicated multidrug-resistant enteric bacilli in retailed tomatoes can cause severe food-borne diseases which public oriented awareness, strategic farm to market surveillance are needed to be intensified.

Ultraviolet-C irradiation maintaining texture and total sugars content of ready to cook baby corn during commercial storage

The aim of this study was to investigate the effects of ultraviolet-C (UV-C) irradiation on the changes in total sugars concentration and texture of ready to cook baby corn during cold storage. The baby corns were irradiated with UV-C at the dose of 0 (control), 2.2, 4.4 and 6.6 kJ m^-2 and then stored at 5 ± 1 °C for 7 days. The results showed that the losses of total sugars were delayed by UV-C irradiation treatments. All the UV-C treatments significantly maintained the firmness of the treated baby corn samples and prevented the increase in electrolyte leakage, especially at 4.4 kJ m^-2. Compared to control sample, the 4.4 kJ m^-2 UV-C irradiated baby corn retarded the depolymerisation of pectin substances by suppressing the polygalacturonase and pectin methyl esterase activities. Therefore, the dose of 4.4 kJ m^-2 could be a feasible alternative UV-C treatment maintaining texture and the total sugar concentration of ready to cook baby corn during commercial storage.

UV-C treatment enhances organic acids and GABA accumulation in tomato fruits during storage

Tomato fruits contain much organic acids and γ-aminobutyric acid (GABA) during ripening which are beneficial to human health. The effects of 4 kJ/m² UV-C treatment on the contents of organic acids and GABA, and the expression of related genes in tomato fruits during storage at 13 °C were investigated. The results showed that UV-C treatment significantly increased the organic acids and total soluble protein contents, whereas decreased the free amino acids and glutamate contents. Besides, UV-C treatment enhanced GAD activity while reduced GABA-T activity, which resulted in accumulation of GABA. Moreover, the genes involved in the biosynthesis of organic acids and GABA were up-regulated, including CS, PEPC1, PEPC2, mMDH, cMDH, GAD1, GAD2, and GAD3, while GABA-T1 and GABA-T3 which involved in GABA degradation were obviously decreased by UV-C treatment. These results indicated that UV-C treatment might be an effective approach to accumulate organic acids and GABA during tomato fruits ripening.

Metabolic features underlying the response of sweet cherry fruit to postharvest UV-C irradiation

The impact of ultraviolet-C (UV-C) irradiation on sweet cherry fruit was studied. Following harvest, fruits (cv. Sweetheart) were exposed to different doses of UV-C (0, 1.2, 3.0 or 6.0 kJ m^-2) and then cold stored (0 °C) for 10 days. Treatments with UV-C delayed most ripening features and reduced pitting symptoms, particularly following prolonged UV-C application. Also, application of the highest UV-C dose inhibited pectin degradation and delayed skin resistance to penetration. An activation of antioxidants capacity and bioactive compounds, such as flavonoids and phenolics was observed. Illumination with UV-C diminished respiration and altered metabolite profile in whole fruit and skin samples. Several amino acids (eg., threonine and aspartate), sugars, (eg., glucose and fructose) and alcohols (e.g., inositol and mannitol) were modulated by long-term UV-C treatment in whole cherry fruit. Various metabolites, including malate, galacturonate, oxoproline and glutamine were also modulated by UV-C skin tissue. These data enhance our understanding of UV-C function in fruit biology.

UV-C treatment promotes quality of early ripening apple fruit by regulating malate metabolizing genes during postharvest storage

Early ripening apples are usually used for fresh marketing because of short storage life, although they are with high acid and low sugar contents. Understanding the malate metabolism in fleshy fruit and underpinning process during ripening is crucial for particular crop improvement where acidity is a concern for direct consumption or further processing. In this research, a traditional Chinese apple cultivar ‘Hongyu’, which belongs to early ripening apple cultivar, were freshly harvested at commercial maturity stage (120 Days after full bloom) and used for different storage temperature (4°C, 20°C) and UV-C treatment (following storage at 20°C after treatment). Simple sugars (glucose, sucrose, and fructose) and organic acids (malic, and oxalic) were assessed after 14 d of storage. Compared to fruits stored at 20°C, the malate content in fruits stored at 4°C significantly higher, while it was decreased significantly in UV-C treated fruits stored at 20°C after 14 d of storage. The sugar content was almost similar throughout the UV-C-treated fruits and fruits stored at different temperature. The higher ratios of total sugars to total organic acids in UV-C treated fruits after 14 d suggest that UV-C treatment has the potential to improve the taste of early ripening apple cultivars. Considering the significant difference in malate the samples at 14 d of storage were subjected for RNA-seq analysis. Transcriptome analysis revealed that the phenomena underlying this change were governed by metabolism of malate by the regulation of NADP-malic enzyme (NADP-ME) and phosphoenolpyruvate carboxylase kinase (PEPCK) in apple during postharvest storage. This transcriptome profiling results have specified the transcript regulation of malate metabolism and lead to possible taste improvement without affecting the other fruit quality attributes.

Improving the storage quality of Tahitian limes (Citrus latifolia) by pre-storage UV-C irradiation

UV-C (180-280 nm) has been shown to extend the postharvest shelf-life of many horticulture crops. In this study, Tahitian limes (Citrus latifolia) were exposed to 0, 3.4, 7.2 and 10.5 kJ m^-2 UV-C then stored for 28 days in air at 10 °C and 80% RH. Weight loss, peel colour, calyx abscission, ethylene production, respiration rate, total soluble solids (TSS), titratable acidity (TA) and acceptability index were assessed. The results showed that UV-C treatment maintained lime peel green colour and retained calyx attachment after 28 days storage. UV-C treatment also affected endogenous ethylene production and respiration rate, where the highest UV-C treatment (10.5 kJ m^-2) maintained low ethylene production and low respiration rates after 28 days storage with no differences between the different UV-C intensities. In terms of fruit acceptability, limes were exposed to 10.5 kJ m^-2 UV-C had a 60% acceptability index after 28 days storage, while untreated control fruit retained acceptability of 39%. In general, the pre-storage UV-C treatments did not affect fruit weight loss, TSS or TA contents during storage.

Isolation of Polygalacturonase-Producing Bacterial Strain from Tomatoes (Lycopersicon esculentum Mill.)

Background

Polygalacturonase (EC 3.2.1.15) enzyme aids in microbial spoilage of fruits and vegetables. It is very important to find economical ways to producing the enzyme so as to achieve maximum yield in industries due to its use at different areas of production process.

Methods

Isolation of polygalacturonase-producing bacterial strain from tomatoes (Lycopersicon esculentum Mill.) was studied. Polygalacturonase-producing bacterial strains were isolated and screened from tomatoes stored at normal laboratory temperature (25 ± 2°C). They were identified based on their morphological, biochemical, and molecular characteristics. The enzyme produced was partially purified by the ammonium sulphate precipitation method. Molecular weights and optimum conditions for best enzyme activity were obtained by SDS PAGE technique.

Results

Five bacterial isolates resulted after screening. Bacterial strain code B5 showed highest polygalacturonase activity. Optimum conditions for polygalacturonase PEC B5 were maintained at pH 4.5; temperature 35°C; substrate concentration 0.3 mg/ml, and best activity at less than 5 min of heating. The enzyme PEC B5 was found to weigh 65 kDa and 50 kDa for crude and partially purified aliquots, respectively. The result of 16S rRNA gene sequencing revealed bacterial strain code B5 as Enterobacter tabaci NR146667 having 79% similarity with the NCBI GenBank.

Conclusion

Microorganisms should be developed for large-scale production of enzymes in developing countries.

Combined postharvest UV-C and 1-methylcyclopropene (1-MCP) treatment, followed by storage continuously in low level of ethylene atmosphere improves the quality of Tahitian limes

The green Tahitian limes (Citrus latifolia) were exposed to 7.2 kJ m^-2 UV-C and 0.5 μL L^-1 1-methylcyclopropene (1-MCP) treatments both separately and in combination. After treatment, fruit were stored in ethylene free (i.e. air containing < 0.005 μL L^-1) or 0.1 μL L^-1 ethylene at 20 °C and 100% RH. The results showed that UV-C treatment delayed skin degreening and reduced endogenous ethylene production compared to untreated control fruit, however these effects reduced over the storage time. As expected, 1-MCP inhibited ethylene production, reduced calyx abscission and retained peel greenness during the storage. Both of the combination treatments, 1-MCP + UV-C and UV-C + 1-MCP reduced endogenous ethylene production and delayed skin yellowing. In all treatments, UV-C and 1-MCP resulted in lower fruit respiration rates than untreated control fruit, however this effect diminished during 7 and 14 days storage for fruits stored in air and 0.1 μL L^-1 ethylene atmosphere, respectively. There was no difference in weight loss, SSC, TA and SSC/TA ratio between the treatments and storage conditions. The results suggest that a pre-storage UV-C treatment, followed by storage at low level of ethylene improves the quality of limes, with the additional improvement when combined with 1-MCP treatment prior or after UV-C irradiation.

Effect of ultraviolet irradiation on postharvest quality and composition of tomatoes: a review

Ultraviolet (UV) irradiation has recently emerged as a possible alternative to currently used postharvest phytosanitary treatments. Research has also highlighted other benefits associated with UV irradiation in postharvest technology. This review presents the effects of UV irradiation on postharvest and nutritional quality of tomatoes. The application of UV irradiation on tomatoes is discussed including its effect on biological (respiration rate, ethylene production and microbial growth), physico-chemical (firmness, colour, total soluble solids and titratable acidity) and nutritional (vitamins, carotenoids, phenolic and antioxidants) quality. UV-treated tomatoes have shown resistance to microbial growth and decay. Although UV irradiation reduces the loss of vitamin C during storage, the loss of vitamin E remains a concern. UV treatments lead to higher antioxidant capacity, flavonoids and phenolic content. UV irradiation significantly reduced carotenoids in certain cultivars. Based on the literature reviewed, the success of UV irradiation treatments is cultivar-dependent. While improved retention of phytochemicals has been reported in UV-C treated fruit, increased losses have been reported in certain cultivars. Research efforts on the development of cultivar-specific UV irradiation protocols are warranted. The effect of harvest maturity and seasonal differences in the efficacy of UV treatments is required to be investigated.

Preharvest ultraviolet-C irradiation: Influence on physicochemical parameters associated with strawberry fruit quality

Postharvest ultraviolet-C (UV-C) hormesis has been shown effective for the treatment of the edible part of several horticultural crops such as strawberry fruit; however, there is a lack of information on its potential preharvest impact. In the present study three strawberry cultivars (Fragaria × ananassa Duch. 'Albion', 'Charlotte' and 'Seascape') were exposed to UV-C during two growth seasons for a period of three weeks. Treatment begins when the first flowers were wide open and fruits at commercial maturity were harvested within one week after UV treatment. The physicochemical quality parameters of the fruits harvested from the treated plants were compared to those of the fruits of the untreated control plants. Preharvest UV-C treatment tended to increase fruit firmness in all cultivars with significant differences declared only for 'Albion' and 'Seascape' in season 2. Fruits from treated plants were generally redder but a significant difference was observed only for cultivar 'Charlotte' in the second growing season. Other color attributes were not affected by UV-C, neither were organic acids, simple sugars, soluble solids content (SSC), titratable acidity (TA) and pH, although in most cases slight decreases were noticed. Cultivar and growing season were the factors that mostly influenced on the parameters under study. The present study show that cumulative preharvest UV-C treatment of 3.6 kJ m^-2 did not adversely affected important strawberry quality parameters.