Green Bell Pepper Research Articles

Effect of temperature and modified atmosphere packaging on overall quality of fresh-cut bell peppers

The effect of vacuum packaging (VP) and modified atmosphere packaging without vacuum (MAP) on shelf-life of fresh-cut green bell pepper stored at 5°C and 10°C were evaluated. In-package atmosphere, overall quality, percentage of leaked juice, texture, ascorbic acid content, ethanol and acetaldehyde, and microbial growth, were evaluated at different intervals of storage. MAP-fresh-cut peppers presented better visual quality, less leaked juice and higher firmness than those stored under VP. Microbiological and quality analysis revealed a limit of shelf-life of 14 and 21 days, when fresh-cut peppers were stored at 10°C and 5°C, respectively. We conclude that MAP could be used to maintain quality attributes of fresh-cut peppers for up 21 days at 5°C.

Biocatalytic production of 2( E)-hexenal from hydrolysed linseed oil

Natural 2( E)-hexenal was produced in two steps from hydrolysed linseed oil, which contains the most linolenic acid among the available natural sources. In the first step 13-hydroperoxy-9( Z),11( E),15( Z)-octadecatrienoic acid (13-HPOT) was formed from linolenic acid (100 mM) by soybean lipoxygenase-1 (Lox-1) isoenzyme with oxygen as co-substrate. The reaction resulted in 57 mM 13-HPOT with a yield of 62%. In the second step 13-HPOT (20 mM) was cleaved by green bell pepper hydroperoxide lyase resulting in 1.6 mM 2( E)-hexenal and 5.9 mM 3( Z)-hexenal (37% yield for the hexenal isomers together). Hexenals were isolated from the reaction mixture by repeated steam distillations. During distillations the 2( E)-hexenal:3( Z)-hexenal isomer ratio was changed from 0.27 to 7.86 as a consequence of heat.

Enumeration, Resuscitation, and Infectivity of the Sublethally Injured Erwinia Cells Induced by Mild Acid Treatment

ABSTRACT Current knowledge about microbial injury was derived mostly from studies with bacteria associated with processed foods. Demonstration of injury and repair in phytopathogenic bacteria and its implication on pathogen detection and disease ecology have not been reported. The objective of this study was to investigate the lethal and sublethal effects of acetic acid (AA) on soft-rot Erwinia spp. and the limitation of using selective media for isolation of injured cells. Following exposure to 0.3% AA for 6 min, 90 to 99% of E. carotovora subsp. carotovora, E. carotovora subsp. atroseptica, and E. chrysanthemi cells were killed. When AA-treated samples were plated on agar media, the number of bacteria recovered on nonselective media such as brain heart infusion agar was 3 log units higher than that recovered on selective media such as crystal violet pectate (CVP). Lethal and sublethal actions of AA on Erwinia spp. were affected greatly by acid concentration, exposure time, and bacterial strains tested. Injured Erwinia cells were able to repair and regain the ability to grow on CVP when placed in nutrient broth but not in selective broth containing crystal violet and sodium dodecyl sulfate. Injured cells also were able to resuscitate on cut surfaces of cucumber fruit and to induce soft rot on green bell pepper. Together, these results suggest that direct use of selective media for isolation of Erwinia spp. could limit the recovery of injured cells in samples that have been exposed to chemical or physical stresses. Enrichment of these samples in nutrient broth before plating on CVP is expected to improve the detection of injured Erwinia spp.

The effect of washing on physicochemical changes in packaged, sliced green peppers

SummaryWhole green bell peppers (Capsicum annuum L.) were obtained through a local fresh‐cut company. They were washed in a 100 ppm chlorine solution, dried and then sliced into 0.5‐cm wide strips. A bulk sample of slices was divided into four treatments: (1) no wash, (2) one wash in fresh distilled water, (3) two sequential washes in fresh distilled water, and (4) three sequential washes in fresh distilled water. Retention of firmness of the pepper slices during storage at 7 °C improved with the number of washes after cutting. The modification of package atmosphere was less in all wash treatments than in the ‘no wash’ control. The sliced tissues of ‘no wash’ controls had higher levels of acetaldehyde and ethyl acetate. Analysis of the wash water revealed that sequential washes with water removed incremental amounts of acetaldehyde and soluble phenols from the cut surfaces of the tissue. These results show that washing has a dramatic effect on physicochemical measures of quality in green pepper slices, and it is likely that this effect is mediated by the removal of stress‐related compounds produced during the cutting operation. While acetaldehyde and total phenolics were the two stress‐related compounds measured in the wash water, it may be that other compounds removed in the wash water could have contributed to the beneficial effects on quality reported in this study.

MeSA and MeJA increase steady-state transcript levels of alternative oxidase and resistance against chilling injury in sweet peppers ( Capsicum annuum L.)

Methyl salicylate (MeSA) and methyl jasmonate (MeJA) vapors increased resistance against chilling injury in freshly harvested green bell pepper ( Capsicum annuum L. cv Century). The period within 2 days of cold storage was considered the most critical because chilling injury symptom (surface pitting) was not apparent. The expression patterns of alternative oxidase (AOX) and seven other genes involved in defense against oxidative stress before and during the early chilling period suggested that pre-treatment of pepper fruit with MeSA or MeJA vapors increased preferentially the transcript levels of AOX. Overnight treatment with MeSA or MeJA vapors increased transcript levels of AOX (1.5 kb) even at room temperature of 25 °C, whereas no change was observed with untreated control. In addition to the expected 1.5 kb AOX transcript, RNA gel blot analysis revealed an extra 3.5 kb transcript that was induced only at 0 °C. At 0 °C, both AOX transcripts (1.5 and 3.5 kb) reached maximal levels firstly in MeSA treated fruit, secondly in MeJA treated fruit and lastly in controls. Compared with freshly harvested peppers, overnight treatment of wholesaler peppers with MeJA does not increase AOX transcript level and no differences in chilling injury symptom were observed between treated and control fruit. AOX transcript level in peppers from farm and wholesaler were maintained at a high level as long as the fruits were kept at 0 °C. Transcript levels of AOX (1.5 kb) were increased by storage at low temperature but the steady-state mRNA accumulation rate was faster at 0 than at 5 °C. Alternative respiratory pathway was proposed to mediate chilling injury. Here, we show that the increase in AOX transcript levels by MeJA or MeSA before cold treatment was correlated with reduced incidence of chilling injury.

Identification and synthesis of 2-heptanethiol, a new flavor compound found in bell peppers.

2-Heptanethiol was identified for the first time as a constituent of red and green bell pepper extracts. The chemical structure of this new aroma compound was proposed on the basis of mass spectra and retention indices and confirmed by chemical synthesis and nuclear magnetic resonance spectroscopy measurements. Its aroma properties were described as sulfury, onion-like, and vegetable-like, reminiscent of bell pepper at lower concentrations, with an orthonasal detection threshold of 10 microg/L of water. No differences in odor note and threshold value were observed for the enantiomeric forms, which were prepared from enantiopure 2-heptanol by tosylation, followed by thioacetylation and reduction, giving the target thiol enantiomers.

Diphenylamine Inhibits Respiration of Green Bell Peppers

The mechanism by which diphenylamine (DPA) controls superficial scald in apples and reduces chilling injury in green bell peppers [Capsicum annuum L. var. annuum (Grossum Group)] has been assumed to be related to its antioxidant activity. In the present study, DPA inhibited the respiratory activity of green bell pepper fruit as well as oxygen uptake by the mitochondria isolated from them. When the alternative oxidase was inhibited with n-propyl gallate or disulfiram during state 4 respiration, DPA did not further inhibit O2 uptake. Treating green bell peppers with DPA before storage did not alter the induction and abundance of the alternative oxidase protein in mitochondria which was maximally induced in peppers stored at 4 °C. Whether added before or after the uncoupler, 2,4-dinitrophenol, DPA negated the enhanced O2 uptake associated with uncoupling of electron transfer in isolated mitochondria. These observations indicate that DPA inhibits the flow of electrons through the cytochrome path, probably somewhere in the cytochrome bc1 complex. Although the secondary amine function of DPA makes it a powerful antioxidant, the effectiveness of DPA in reducing chilling injury in green bell peppers and superficial scald in apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] also may be due, in part, to its inhibition of respiration.

Activation of the Ah receptor by extracts of dietary herbal supplements, vegetables, and fruits.

The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that can be activated by a structurally diverse range of synthetic and natural chemicals, and it mediates the toxic and biological effects of environmental contaminants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The spectrum of chemicals that bind to and activate the AhR signal transduction pathway and the identity of materials containing AhR active chemicals is only now being defined. Utilizing AhR-dependent gel retardation and reporter gene bioassays, the screening of extracts of 22 dietary herbal supplements and 21 food products (vegetables and fruits) was performed to identify those containing AhR agonists. Several herbal extracts (ginseng, Fo-Ti, white oak bark, licorice, ginkgo biloba, and black cohosh) stimulated AhR DNA binding and gene expression to levels between 20 and 60% of that produced by TCDD. Although some food extracts (corn, jalapeño pepper, green bell pepper, apple, Brussels sprout, and potato) were relatively potent activators of AhR DNA binding (30-50% of TCDD), only corn and jalapeño pepper extracts induced AhR-dependent luciferase reporter gene expression. However, dilution of corn, jalapeño pepper, bell pepper, and potato extracts dramatically increased their ability to induce luciferase activity, suggesting that these extracts contained AhR antagonists whose effectiveness was overcome by dilution. Overall, these results demonstrate that dietary products can be a major source of naturally occurring AhR ligands to which animals and humans are chronically exposed.

Effect of pressure and blanching treatments on endogenous enzymatic activity and vitamin C content of bell pepper fruit

The effect of high pressure and blanching treatments on green bell pepper was studied. Both processes caused changes on pectin methylesterase activity and vitamin C and protein contents. Polygalacturonase activity was not detected in any of the samples studied. There seems to be no significant difference caused by both types of processing.

Hydrocolloid‐Lipid Coating Affect on Weight Loss, Pectin Content, and Textural Quality of Green Bell Peppers

ABSTRACTThree coatings containing a hydrocolloid‐lipid blend combination were developed and applied to green bell peppers. Peppers were refrigerated and monitored over a 5‐week period to determine pectin content and textural quality. Pectin content decrease was significantly (p < 0.05) greater in the uncoated peppers during the storage period. Weight loss also occurred in the uncoated peppers at a significantly greater rate, while respiration rates and puncture score differences were insignificant among all groups. The results indicate that the coatings were effective in maintaining quality during storage. A better procedure is recommended for puncture analysis.

Diphenylamine reduces chilling injury of green bell pepper fruit

Diphenylamine (DPA), an antioxidant widely used to control superficial scald in apples stored at low temperatures, reduced the chilling-induced pitting of green bell pepper (Capsicum annuum L.) fruit in a concentration-dependent manner up to 12 mM. Treatment was effective whether applied as a 2-min dip or injected into the seed cavity prior to storing peppers at 1° C for 6 or 8 days followed by storage at 20° C for an additional 2 days. Ethanol (5%), the solvent used to dissolve the diphenylamine, also reduced chilling injury of green bell peppers, but to a lesser extent than DPA. Changes in all of the chlorophyll fluorescence parameters were observed within 24 h following the exposure of green bell peppers to low temperatures, whereas visible manifestation of chilling injury was not observed until after the peppers had been exposed to several days of low temperatures. Diphenylamine reduced the chilling-induced decline in maximal chlorophyll fluorescence and increased the time taken for maximal chlorophyll fluorescence to occur and the size of the electron acceptor pool. If chilling injury results from oxidative stress induced by low storage temperatures, it is unlikely that chloroplasts were the site of production of active oxygen species in these green bell peppers since they were stored in the dark. The rapidity of chlorophyll fluorescence responses to low temperatures makes chlorophyll fluorescence analysis useful to distinguish between chilling-sensitive and chilling-resistant plant tissues, but does not measure the extent of chilling injury.

Purification of hydroperoxide lyase from green bell pepper (Capsicum annuum L.) fruits for the generation of C6-aldehydes in vitro.

The aim of this work was to compare the efficiency of different extracts of hydroperoxide lyase from green bell peppers in producing aldehydes: a crude extract, a chloroplastic fraction, and a purified enzyme were investigated. From a crude extract, the HPO lyase was purified by ion-exchange chromatography with a 22.3-fold increase in purification factor. Analysis by SDS-PAGE electrophoresis under denaturating conditions showed only one protein with a molecular weight of 55 kDa, whereas size-exclusion chromatography indicated a molecular weight of 170 kDa. A maximum of 7500 mg of aldehydes per g of protein was obtained with the purified enzyme within 20 min of bioconversion compared to 392 and 88 mg of aldehydes per g of protein within 50 and 60 min, respectively, for the chloroplast fraction and the crude extract.

Analysis of Native Microflora and Selection of Strains Antagonistic to Human Pathogens on Fresh Produce

The native microflora of three types of produce (green bell peppers, Romaine lettuce, and prepeeled baby carrots) and two types of sprouting seeds (alfalfa and clover) were investigated. Aerobic plate count (APC) for each produce or seed type as determined on Pseudomonas agar F (PAF) with incubation at 28°C was in the range of 4 to 7 log CFU per g of tissue or seed. There was no significant difference (P ≥ 0.05) in APC when the determinations were made with three agar media including PAF, brain heart infusion agar, and plate count agar. However, the APC as determined from plates that were incubated at 28°C was significantly (P ≤ 0.05) higher than with incubation at 37°C. Fluorescent pseudomonads accounted for 23 to 73% of APC and 6 to 18% of APC recovered from carrots, pepper, and lettuce were pectolytic. Forty-eight strains of pectolytic bacteria were randomly isolated and identified, respectively, as members of the genera of Pseudomonas, Erwinia, Bacillus, Xanthomonas, or Flavobacterium. Lactic acid bacteria and/or yeast were consistently isolated from baby carrots, lettuce, and sprouting seeds (alfalfa or clover) but not from green bell peppers. Approximately 120 strains of indigenous microflora were tested for their ability to inhibit the growth of Salmonella Chester, Listeria monocytogenes, Escherichia coli, or Erwinia carotovora subsp. carotovora on PAF. Six isolates capable of inhibiting the growth of at least one pathogen were isolated and identified, respectively, as Bacillus spp. (three strains), Pseudomonas aeruginosa (one strain), Pseudomonas fluorescens (strain A3), and yeast (strain D1). When green pepper disks were inoculated with strains A3 and D1, the growth of Salmonella Chester and L. monocytogenes on the disks was reduced by 1 and 2 logs, respectively, over a period of 3 days. Application of strains A3 and D1 as potential biopreservatives for enhancing the quality and safety of fresh produce is discussed.

Stress-induced changes in ubiquinone concentration and alternative oxidase in plant mitochondria.

We have investigated the influence of stress conditions such as incubation at 4 degrees C and incubation in hyperoxygen atmosphere, on plant tissues. The ubiquinone (Q) content and respiratory activity of purified mitochondria was studied. The rate of respiration of mitochondria isolated from cold-treated green bell peppers (Capsicum annuum L) exceeds that of controls, but this is not so for mitochondria isolated from cold-treated cauliflower (Brassica oleracea L). Treatment with high oxygen does not alter respiration rates of cauliflower mitochondria. Analysis of kinetic data relating oxygen uptake with Q reduction in mitochondria isolated from tissue incubated at 4 degrees C (bell peppers and cauliflowers) and at high oxygen levels (cauliflowers) reveals an increase in the total amount of Q and in the percentage of inoxidizable QH2. The effects are not invariably accompanied by an induction of the alternative oxidase (AOX). In those mitochondria where the AOX is induced (cold-treated bell pepper and cauliflower treated with high oxygen) superoxide production is lower than in the control. The role of reduced Q accumulation and AOX induction in the defense against oxidative damage is discussed.

Texture of rehydrated dried bell peppers modified by low‐temperature blanching and calcium addition

Diced green bell pepper was blanched twice, once at 51–79 °C for 19–61 min, and once at 95 °C for 3 min, and dried. The firmness of rehydrated samples was measured by puncture, and optimum conditions assessed by response surface methodology. The optimized model showed that, blanching at 65 °C for 49 min gave a 64% increase in puncture force over the control. The optimum temperature was used to evaluate the effect of adding CaCl2. The dices were blanched twice, once at 65 °C for 3 min in either 0 or 4% CaCl2, secondly in either 0 or 2% CaCl2 solution at 95 °C for 3 min. In the second case the dices had been held at room temperature for 0–30 min before treatment. Adding CaCl2 increased puncture force significantly (P ≤ 0.05). The best results, those which gave greatest firmness, were obtained by blanching at 65 °C for 3 min in 4% CaCl2, holding for 16 min after blanching, followed by a secondary blanching at 95 °C in 2% CaCl2.

Reduction of superoxide production by mitochondria oxidizing NADH in the presence of organic acids

Effects of multiple substrates on oxygen uptake and superoxide production by mitochondria isolated from the pericarp tissue of green bell pepper ( Capsicum annuum L.) were studied. Mitochondria isolated from peppers stored at 4 °C for 5 and 6 days had higher rates of oxygen uptake and were less sensitive to cyanide than mitochondria isolated from freshly harvested peppers. Succinate enhanced state 2 and state 4 rates of oxygen uptake with exogenous NADH in the absence of cytochrome path inhibitors, but not state 3 rates by mitochondria isolated from either freshly harvested or cold-stored bell peppers. The sensitivity of NADH oxidation to cyanide was reduced by both malate and succinate in mitochondria from cold-stored bell peppers, whereas only succinate was effective in mitochondria from freshly harvested peppers. Mitochondria isolated from both freshly harvested peppers and those stored at 4 °C for 5 and 6 days produced superoxide in the absence of exogenous substrates. Superoxide production by mitochondria from freshly harvested bell peppers increased when the mitochondria were supplied with malate, succinate or NADH, but only NADH enhanced superoxide production by mitochondria from cold-stored peppers. Both succinate and malate reduced the production of superoxide by mitochondria isolated from cold-stored bell peppers. Succinate and malate as second substrates also reduced the production of superoxide with NADH by mitochondria from both freshly harvested and cold-stored bell peppers. Malonate, a competitive inhibitor of succinate dehydrogenase, was inhibitory to oxygen uptake and to superoxide production. Mitochondria isolated from cold-stored bell peppers converted succinate to pyruvate at 25 °C at considerably higher rates than those of mitochondria from freshly harvested bell peppers. Since pyruvate has been shown to activate the alternative oxidase and the presence of pyruvate is essential for continued alternative oxidase activity, we suggest that pyruvate limits superoxide production by enhancing the flow of electrons through the alternative path. A direct scavenging of superoxide by succinate, malate and pyruvate, however, cannot be ruled out.

Organoleptic impact of 2-methoxy-3-isobutylpyrazine on red bordeaux and loire wines. Effect of environmental conditions on concentrations in grapes during ripening.

The 2-methoxy-3-isobutylpyrazine content in grapes and red wines was assayed by stable isotope dilution gas chromatography-mass spectrometry, following vapor extraction and purification on a cation resin microcolumn. The threshold beyond which the green bell pepper character is marked in wines has been determined. From a comparison of the 2-methoxy-3-isobutylpyrazine concentrations of 50 red Bordeaux and Loire wines from different vintages and grape varieties (Cabernet Sauvignon, Cabernet franc, and Merlot) with the intensity of the green bell pepper character as perceived on tasting, the threshold value was estimated to be 15 ng/L. Statistical analysis of the 2-methoxy-3-isobutylpyrazine concentrations of 89 red Bordeaux wines showed that Cabernet wines were more commonly affected by this vegetative character. Changes in the 2-methoxy-3-isobutylpyrazine concentration as the grapes ripen are affected by the environmental and cultural conditions (soil, climate, training system, etc.). A very good correlation was shown between the breakdown of malic acid and 2-methoxy-3-isobutylpyrazine as the grapes ripened, irrespective of grape variety, type of soil, or weather conditions.

516 Does Diphenylamine Reduce Chilling Injury in Green Bell Peppers?

Diphenylamine has been used to reduce low-temperature-induced storage scald of apples for decades. Its effectiveness in reducing scald has been attributed to its antioxidant properties. Oxidative reactions have also been implicated in chilling injury of other commodities, including green bell peppers (Capsicum annuum L.). Diphenylamine was applied as a dip at rates of 500 to 2000 ppm to green bell peppers prior to storing them for 7 days at 1 °C. The development of sheet pitting, the most common visible symptom of chilling injury in bell peppers, was inhibited almost completely by diphenylamine. Diphenylamine, however, only slightly reduced the chilling-induced decrease in chlorophyll fluorescence ratios. Darkening of the vascular tissues of the calyxes and seed darkening, which are also symptoms of chilling injury, were not prevented by diphenylamine. Thus, diphenylamine either did not get into all of the sites of oxidative reactions or some of the manifestations of chilling injury are initiated by processes other than oxidative ones.

Preplant Slow‐Release Nitrogen Fertilizers Produce Similar Bell Pepper Yields as Split Applications of Soluble Fertilizer

Slow‐release N materials are used to reduce N leaching losses from sandy soils and extend N availability over a growing season. The objective of this research was to examine the effectiveness of preplant sulfur‐coated urea (SCU) and polyolefin resin‐coated urea (PCU) N fertilizers compared to split applications of soluble fertilizer on green bell pepper (Capsicum annuum L.) yield and quality. The 3‐yr experiment consisted of green bell peppers grown on 15‐cm raised beds utilizing plastic mulch and drip irrigation. Treatments were N source (preplant SCU, preplant PCU, and fertigated ammonium nitrate) and N rate (90, 135, 180, or 225 kg N ha−1). Ammonium nitrate (AN) was applied as a split application, with 20% preplant and 80% applied every‐other week in five equal applications. Other N sources were applied 100% preplant. A zero N control was also included. Collected data included plant height, leaf N content, and fruit yield and quality. In two of three years pepper yield was maximized at or near the Alabama recommended rate of 135 kg N ha−1. Nitrogen source rarely affected the partitioning of harvested peppers into grade groups. Adding N from any N source decreased percent nonmarketable yield (cull) and increased the percentage of marketable yield that was large (U.S. 1) peppers. There were few consistent differences in pepper yield or quality due to N source. Given cost considerations of drip application and N sources, slow‐release N materials may be a viable option for small‐scale growers not using drip application systems.

Effects of Ascorbic Acid-Rich Bell Pepper on Development of Bactrocera latifrons (Diptera: Tephritidae)

A survey of published nutritional data of ingredients currently used in larval diet for the fruit fly Bactrocera latifrons (Hendel) indicated low levels of ascorbic acid in the artificial diet in comparison to a preferred host (bell pepper, Capsicum annuum L.). Incorporation of various amounts of green bell pepper (fresh or dehydrated powder) into larval diet significantly affected larval development by increasing pupal recovery up to 21%, adult emergence up to 17.5%, and the overall growth index. Pupal weight remained similar to that of a control diet. An optimal amount of ascorbic acid phosphate (5 mg/g diet) in the diet also improved development, especially in terms of pupal recovery and adult emergence. Addition of ascorbic acid phosphate (>15 mg/g of diet) produced detrimental effects (lengthened the larval period, decreased the pupal recovery, reduced pupal weight and overall growth index). Substituting bell pepper for carrot powder in the standard B. latifrons larval diet or supplementing the standard diet with ascorbic acid phosphate would be beneficial for mass rearing of B. latifrons.