Charles F. Forney

Improving the thiobarbituric acid-reactive-substances assay for estimating lipid peroxidation in plant tissues containing anthocyanin and other interfering compounds

Abstract. The occurrence of malondialdehyde (MDA), a secondary end product of the oxidation of polyunsaturated fatty acids, is considered a useful index of general lipid peroxidation. A common method for measuring MDA, referred to as the thiobarbituric acid-reactive-substances (TBARS) assay, is to react it with thiobarbituric acid (TBA) and record the absorbance at 532 nm. However, many plants contain interfering compounds that also absorb at 532 nm, leading to overestimation of MDA values. Extracts of plant tissues including purple eggplant (Solanum melongena L.) fruit, carrot (Daucuscarota L.) roots, and spinach (Spinacia oleracea L.) leaves were assessed for the presence of MDA and other non-MDA compounds absorbing at 532 nm. A method described herein corrects for these interferences by subtracting the absorbance at 532 nm of a solution containing plant extract incubated without TBA from an identical solution containing TBA. The reliability and efficiency of this spectrophotometric method was assessed by altering the relative ratios of exogenous MDA additions and/or extracts of red cabbage (Brassica oleracea L.) leaves containing interfering compounds and then measuring MDA recovery. Reliability was also validated through high-performance liquid chromatography and high-performance liquid chromatography-mass spectrometry techniques. Results indicated that over 90% of exogenously added MDA could be recovered through the improved protocol. If there were no corrections for interfering compounds, MDA equivalents were overestimated by up to 96.5%. Interfering compounds were not detected in vegetables such as lettuce (Lactuca sativa L.) and spinach which had low or negligible concentrations of anthocyanidin derivatives. Comparisons between the TBARS method presented here and two currently accepted protocols indicated that the new modified method exhibits greater accuracy for quantifying TBA-MDA levels in tissues containing anthocyanins and/or other interfering compounds. This modified protocol represents a facile and rapid method for assessment of lipid peroxidation in virtually all plant species that contain interfering compounds.

Effect of ozone pre-conditioning on quality and antioxidant capacity of papaya fruit during ambient storage

The objective of this study was to compare the physico-chemical characteristics and antioxidant activity of ozone-treated papaya fruit and untreated fruit. Freshly harvested papaya fruit were exposed continuously to ozone fumigation (0, 1.5, 2.5, 3.5 and 5ppm) for 96h prior to ambient storage at 25±3°C and 70±5% relative humidity (RH) for up to 14days. The fruit exposed to 2.5ppm ozone had higher levels of total soluble solids (25.0%), ascorbic acid content (12.4%), β-carotene content (19.6%), lycopene content (52.1%), and antioxidant activity (30.9%), and also reduced weight loss (11.5%) at day 10 compared to the control. The sensory attributes of papaya treated with 2.5ppm ozone was superior in sweetness and overall acceptability. These results support the application of ozone as a non-thermal and safe food preservation technique for papaya which can benefit both the producers and consumers.

Interaction of ozone and negative air ions to control micro-organisms

Aims:  The aims of this study were to investigate the effect of ozone and/or negative air ions (NAI) on the viability of bacteria.

Ethylene and 1-MCP regulate major volatile biosynthetic pathways in apple fruit

The effects of ethylene and 1-methylcyclopropene (1-MCP) on apple fruit volatile biosynthesis and gene expression were investigated. Statistical analysis identified 17 genes that changed significantly in response to ethylene and 1-MCP treatments. Genes encoding branched-chain amino acid aminotransferase (BCAT), aromatic amino acid aminotransferase (ArAT) and amino acid decarboxylases (AADC) were up-regulated during ripening and further enhanced by ethylene treatment. Genes related to fatty acid synthesis and metabolism, including acyl-carrier-proteins (ACPs), malonyl-CoA:ACP transacylase (MCAT), acyl-ACP-desaturase (ACPD), lipoxygenase (LOX), hydroperoxide lyase (HPL), alcohol dehydrogenase (ADH), pyruvate decarboxylase (PDC2), β-oxidation, acyl-CoA synthetase (ACS), enoyl-CoA hydratase (ECHD), acyl-CoA dehydrogenase (ACAD), and alcohol acyltransferases (AATs) also increased during ripening and in response to ethylene treatment. Allene oxide synthase (AOS), alcohol dehydrogenase 1 (ADH1), 3-ketoacyl-CoA thiolase and branched-chain amino acid aminotransferase 2 (BCAT2) decreased in ethylene-treated fruit. Treatment with 1-MCP and ethylene generally produced opposite effects on related genes, which provides evidence that regulation of these genes is ethylene dependent.

Characterization of Changes in Polyphenols, Antioxidant Capacity and Physico-Chemical Parameters during Lowbush Blueberry Fruit Ripening

Changes in major polyphenols, antioxidant capacity, and selected physico-chemical parameters were examined in lowbush blueberry during fruit ripening. Polyphenols (phenolic acids, flavonols, flavan-3-ols, and anthocyanins), density, soluble solid content, pH, titratable acidity, sugars, organic acids, and antioxidant capacity were determined in fruits of four maturities: green, pink/red, blue, and over-mature. Highest concentrations of flavonols, flavan-3-ols, and phenolic acids were in green fruits: 168 ± 107, 119 ± 29 and 543 ± 91 mg/100 g dry weight (DW) respectively. Highest anthocyanin levels were found in blue and over-mature fruits (1011–1060 mg/100 DW). Chlorogenic acid was the most abundant phenolic acid and quercetin-3-O-galactoside the most abundant flavonol in all maturities. Epicatechin was the most abundant flavan-3-ol in green fruits (80 ± 20 mg/100 DW), and catechin was the most abundant in other maturity stages. Increase of glucose and fructose and decrease of organic acids were observed during fruit ripening. Among six organic acids found, quinic acid (1.7–9.5 mg/100 mg DW) was the most abundant throughout the fruit ontogeny. Soluble solids, pH, and density increased with maturity while, titratable acidity decreased. These findings can be helpful in optimizing harvest and processing operations in lowbush blueberry fruits.

Blueberry and cranberry fruit composition during development

Compositional changes that occur during fruit development affect both the organoleptic and nutritional quality of small fruit. Compositional changes in blueberry (Vaccinium corymbosum L) and cranberry (Vaccinium macrocarpon Aiton) fruit were determined at 3 maturities (white, turning and fully colored) during 2 seasons by analyzing sugar, acid, total phenolic, and total anthocyanin composition, ORAC antioxidant capacity, and fruit firmness. In blueberry fruit, the primary sugars were glucose and fructose, which increased as fruit ripened. Citric acid comprised 77 to 87% of the organic acids in blueberry fruit. In addition, quinic and malic acids comprised 4 to 11% of total acids and small amounts of succinic, tartaric, and shikimic acids were present. Total acids declined 68% during fruit ripening. Total phenolics were greatest in white fruit and anthocyanins were greatest in blue fruit. Antioxidant capacity declined as fruit ripened from white to turning. Fruit firmness decreased about 80% as fruit ripened. In cranberry fruit, sugar concentration increased slightly as fruit ripened with glucose comprising about 80% of the total sugars. Acid content decreased 22% during ripening primarily due to a decline in citric acid. Quinic and malic acids increased slightly during ripening. Total anthocyanins increased as color developed, while total phenolics and antioxidant capacity remained relatively constant. In contrast to blueberries, red cranberry fruit were firmer than white or turning fruit.

Phytotoxocity of vapour phase hydrogen peroxide to Thompson Seedless grapes and Botrytis cinerea spores

Abstract The tolerance of Botrytis cinerea Pers. spores and Thompson Seedless grapes ( Vitis vinifera L.) to vapour phase hydrogen peroxide (H 2 O 2 vapour) at various concentrations and temperatures was determined. The germination rate of botrytis spores decreased logarithmically with exposure time to H 2 O 2 vapour. Treatments of 0.27 and 0.55 mg l −1 H 2 O 2 vapour at 20 or 30 °C, respectively, required 10.5 and 5.7 min to kill 99% of the spores. Grapes did not develop visible injury until they were exposed to 0.55 mg l −1 H 2 O 2 vapour for 6 h at 40 °C. Injury developed as a yellow-brown discoloration of the fruit and stems. Discoloration increased with time of exposure and concentration of H 2 O 2 vapour. High treatment temperatures also increased the rate of discoloration. Prolonged exposure to H 2 O 2 vapour caused increased water loss and loss of firmness of the grapes. Grapes were able to tolerate exposures of 0.27 mg l −1 H 2 O 2 vapour at 40 °C for 24 h with no visible injury. The difference in the tolerance of botrytis spores and grapes to H 2 O 2 vapour may allow its use to control botrytis bunch rot in stored table grapes.

Targeted quantitative proteomic investigation employing multiple reaction monitoring on quantitative changes in proteins that regulate volatile biosynthesis of strawberry fruit at different ripening stages

A targeted quantitative proteomic investigation employing the multiple reaction monitoring (MRM, SRM) technique was conducted on strawberry fruit at different development stages. We investigated 22 proteins and isoforms from 32 peptides with 111 peptide transitions, which may be involved in the volatile aroma biosynthesis pathway. The normalized protein abundance was significantly changed in coincidence with increased volatile production and advanced fruit maturities. Among them, alcohol acyltransferase (AAT), quinone oxidoreductase (QR), malonyl Co-A decarboxylase, (MLYCD), pyruvate decarboxylase (PDC), acetyl Co-A carboxylase (ACCase), and acyl Co-A synthetase (ACAs) were increased significantly. Several alcohol dehydrogenases (ADHs), and 3-oxoacyl-ACP synthase were significantly decreased. Furthermore, the expression of seven genes related to strawberry volatile production was also investigated using real-time qPCR. Among the tested genes, QR, AAT, ACCase, OMT, PDC and ADH showed increased up-regulation during fruit ripening, while 3-isopropylmalate dehydrogenase (IMD) decreased. Strong correlation between quantitative proteomic data and gene expression suggested that AAT, QR, ACCase, and PDC played critical roles in volatile biosynthesis of strawberry during fruit ripening. Poor correlation between protein abundance and gene expression of ADH was found.

A method to detect diphenylamine contamination of apple fruit and storages using headspace solid phase micro-extraction and gas chromatography/mass spectroscopy.

Analysis of headspace concentrations of diphenylamine using solid phase micro-extraction (SPME) was examined for its suitability to detect DPA contamination and off-gassing in apple (Malus domestica) fruit, storage rooms and storage materials. Four SPME fibre coatings including polydimethylsiloxane (PDMS, 100 μm), PDMS/divinylbenzene (PDMS/DVB), Polyacrylate (PA) and PDMS 7 μm were evaluated. The average limits of detection and of quantification for head space DPA ranged from 0.13 to 0.72 μg L(-1) and 0.42 to 2.35 μg L(-1), respectively. Polyacrylate was identified to be the most suitable and compatible fibre for DPA analysis in apple samples, because of its high sensitivity to DPA and low fruit volatile interferences. SPME techniques were further applied to study contamination of DPA in apples, storage rooms and packaging materials. DPA was found in the air of storage rooms containing apples that were not treated with DPA. Wood and plastic bin material, bin liners, and foam insulation all adsorbed and off-gassed DPA and could be potential sources of contamination of untreated apples.

Row Covers to Delay or Advance Maturity in Highbush Blueberry

SUMMARY A wide variety of hardy highbush blueberry (Vaccinium corymbosum L.) cultivars are suitable for cultivation in parts of North-Eastern Canada, and especially Nova Scotias Annapolis Valley (latitude 45 EN). The object of this research was to investigate the potential to expand late market opportunities for exported fruit from northern areas by using a combination of controlled atmosphere (CA) storage and in-field row covers to delay fruit maturity in two cultivars (‘Bluegold’ and ‘Brigitta’), and to advance maturity in the cultivar ‘Elliott’, that normally matures too late for full harvest at this latitude. Covering ‘Blue-gold’ and ‘Brigitta’ with 50% shading from time of fruit set to harvest delayed full harvest by about 2.5 weeks in the first year. Yield decreases were recorded in the 2nd year of covering suggesting that covering with this density may diminish long-term yield potential. Fruit quality following after 6 weeks of CA storage (10% CO2, 16% O2, 0°C) was not affected by shading and after 42 days of storage fruit showed very little decay. Decay increased substantially after 63 days of storage. A removable row cover (6 mil polyethylene) advanced maturity in ‘Elliott’ in the first year by between 10 and 14 days, but this advancement was not repeated in the second season. In the first year, covering the crop only until petal drop was nearly as effective as covering throughout the season. Yield from covered plants was increased about 25% in the first year as compared with the controls, but this increase was not realized in the second year. ‘Elliott’ fruit from all treatments stored successfully for up to 42 days, and up to 63 days in control plants; fruit from covered plants showed a 30% decline in marketability when subjected to an additional 7 days in air at 7°C following 63 days in CA.