[Show abstract][Hide abstract] ABSTRACT: The effects of a waiting period at room temperature ( approximately 22 degrees C) before refrigerating fresh-cut watermelon, cantaloupe and honeydew pieces contaminated with Salmonella on survival of the inoculated pathogen were investigated. Whole cantaloupes, honeydew melons and watermelons were washed with water, and fresh-cut pieces from individual melons were prepared and inoculated with a five strain cocktail of Salmonella at 10(5)cfu/ml. Populations of aerobic mesophilic bacteria, yeast and mold and Pseudomonas spp. were higher for fresh-cut cantaloupe than for fresh-cut watermelon and honeydew immediately after preparation. Populations of Salmonella, aerobic mesophilic bacteria, yeast and mold and Pseudomonas ssp. in fresh-cut melons left at room temperature for up to 5h before refrigeration were significantly (P<0.05) higher than populations in fresh-cut melons stored at 5 degrees C immediately after preparation. Populations of Salmonella recovered in fresh-cut melon after inoculation with the cocktail of Salmonella strains averaged 2 log(10)cfu/g for all three types of melons. Populations in fresh-cut watermelon and honeydew pieces declined by 1 log when stored immediately at 5 degrees C for 12 days, while the populations in fresh-cut cantaloupe did not show significant (P>0.05) changes. Populations of Salmonella in fresh-cut melons stored immediately at 10 degrees C for 12 days increased significantly (P<0.05) from 2.0 to 3.0 log(10)cfu/g in watermelon, 1.9 to 3.0 log(10)cfu/g in honeydew and 2.0 to 3.6 log(10)cfu/g in cantaloupe pieces. Holding freshly prepared, contaminated fresh-cut melon pieces at 22 degrees C for 3h or more prior to refrigerated storage would increase the chances of Salmonella proliferation, especially if the fresh-cut melons were subsequently stored at an abusive temperature.
[Show abstract][Hide abstract] ABSTRACT: Fresh-cut cantalcupe has been recalled due to the possible presence of Listeria monocytogenes. Several studies have reported that naturally occurring microflora of vegetable surfaces may be antagonistic to pathogen attachment, growth or survival. To test this possibility for L. monocytogenes and cantaloupes, whole melon were treated with water, ethanol (70%) or chlorine (200 ppm) to reduce the native microflora on the melon surfaces. Treated or untreated melons were immersed in a six strain cocktail of L. monocytogenes (107 CFU/mL) for 10 min and then allowed to dry for 1 h inside a biosafety cabinet followed by storage at 5, 10 and 20C for 15 days. Fresh-cut pieces prepared from the treated or untreated melons and directly inoculated with L. monocytogenes (3.48 log CFU/g) were stored under the same conditions listed above. Populations of L. monocytogenes and five classes of native microflora were investigated. Growth of L. monocytogenes in sterile or nonsterile rind and fresh-cut homogenates was also studied. The population of L. monocytogenes recovered from inoculated (103 to 108 CFU/mL) whole melons given no disinfection treatment or washed with water was significantly less (P < 0.05) than that recovered from melons treated with chlorine or EtOH. In general, populations of L. monocytogenes declined on the surface of treated and untreated whole melons and on fresh-cut pieces over the 15 days storage period at the temperatures tested. However, the decline in pathogen populations was less rapid in the presence of reduced populations of native microflora. Higher populations of L. monocytogenes were attained in sterile tissue homogenates than in nonsterile homogenates. Addition of yeast and mold to sterile rind homogenates was highly inhibitory to growth and survival of the pathogen. The results of this study indicate that native microflora of whole cantaloupe inhibited attachment to rind surfaces as well as survival and growth of L. monocytogenes on cantaloupe surfaces and homogenized fresh-cut pieces. Thus, L. monocytogenes recontamination of melons having a reduced level of native microflora following application of a disinfection treatment may be a food safety concern.
[Show abstract][Hide abstract] ABSTRACT: The influence of chlorine or hydrogen peroxide treatment on populations of Escherichia coli 25922 on the external surface of inoculated cantaloupe was investigated. Surface treatment with 70% EtOH, followed by immersion in 108 CFU/mL E. coli inoculum deposited an average of 4.4 log10CFU/cm2 cell population on the cantaloupe surface. The efficncy of washing inoculated cantaloupe was dependent on storage interval between inoculation and treatment. Dipping the cantaloupes in solutions containing 1000 mg/L chlorine or 5% peroxide for 5 min, within 24 h of inoculation, caused a 2 log10 CFU/cm2 reduction of the indigenous surface microflora and a 3–4.0 log10 CFU/cm2 reduction in E. coli. The efficacy was less when the interval between inoculation and treatment exceeded 24 h. Chlorine appeared in be a better antimicrobial agent than hydrogen peroxide against F. coli ATCC 25922 inoculated on cantaloupe surfaces while hydrogen peroxide was better in reducing surface microflora of cantaloupe.
[Show abstract][Hide abstract] ABSTRACT: Growth of Listeria monocytogenes on the surface of fresh peeled potatoes, treated with sulfite or a commercial browning inhibitor (CBI), packaged under vacuum and stored at 4,15 and 28°C was determined. At 4°C, L. monocytogenes did not grow in all treated potatoes even after 21 days. At 15°C, L. monocytogenes grew to 7 log10 CFU/g within 12 days in the potatoes treated with sulfite or CBI. At 28°C, L. monocytogenes population was greater than 3 log10 CFU/g by 24 h in all samples regardless of treatment. Sulfites or a CBI appeared to provide a measure of safety in pre-peeled potatoes packaged under vacuum when kept at proper refrigeration temperatures.
[Show abstract][Hide abstract] ABSTRACT: Fresh tomatoes repeatedly have been associated with major outbreaks of salmonellosis; however, efforts to disinfect them with chlorine or other sanitizing agents have had only mixed success. Our objective was to determine whether hydrogen peroxide (H2O2) treatments would be more efficacious than conventional methods in disinfecting tomatoes containing human pathogens and, at the same time, be noninjurious to quality. Tomatoes were dip inoculated with Escherichia coli NRRL B-766 or a Salmonella cocktail and then held for 0, 24, or 48 h at 4 or 24 °C prior to treatment. Treatments included 200 ppm chlorine (Cl2) at 20 °C for 3 min, water at 20 °C for 3 min or at 60 °C for 2 min, 1% H2O2 at 20 °C for 15 min or at 60 °C for 2 min, and 5% H2O2 at 60 °C for 2, 3, or 5 min. In tomatoes held 48 h postinoculation, the chlorine treatment was only marginally more effective than an equivalent water rinse in reducing the target bacterial population, while the hot water and 1% H2O2 treatments achieved reductions no greater than 1.3 logs. However, application of 5% H2O2 at 60 °C resulted in larger reductions. Efficacy of all treatments decreased as the time interval between inoculation and treatment increased. Greater reductions could not be achieved with 5% H2O2 at 60 °C by increasing the contact time or addition of surfactants, and these treatments caused some quality loss.
[Show abstract][Hide abstract] ABSTRACT: Treatments to control discoloration of minimally processed mushrooms were investigated. Whole or sliced mushrooms were immersed in browning inhibitor solutions and evaluated for color change during storage. Browning was more intense in first break mushrooms than in second, and in unwashed mushrooms compared to washed. However, washing sometimes induced purple discolorations, associated with bacterial lesions. Other discolorations were induced by hypochlorite, 4-hexylresor-cinol, and acidic dips. The most effective treatment was a combination of sodium erythorbate, cysteine, and EDTA at pH 5.5. Addition of preservatives to browning inhibitor dips did not improve storage life. However, dipping in 5% hydrogen peroxide prior to application of browning inhibitors significantly increased shelf-life.
[Show abstract][Hide abstract] ABSTRACT: Treatment of pre-peeled potatoes with heated ascorbic acid (AA)/citric acid (CA) solution to extend shelf-life was investigated. Potatoes were abrasion or high pressure steam peeled, heated for 5–20 min in 1% AA + 2% CA at 45–55°C cooled, and then dipped for 5 min in browning inhibitor (BI) solution containing 4% AA +1% CA +1% sodium acid pyrophosphate. Combined treatment inhibited potato discoloration for 14 days at 4°C compared to 3–6 days with BI treatment alone. Raw material and treatment conditions were selected to minimize graying and textural abnormalities encountered with some treatments. Treatment with heated AA/CA may be an alternative to use of sulfites to control browning in pre-peeled potatoes.
[Show abstract][Hide abstract] ABSTRACT: Treated potato samples were evaluated for browning by tristimulus colorimetry and for browning inhibitor uptake by HPLC. Treatment effectiveness was greatly improved by reducing pH to 2.0 with phosphoric acid to inhibit endogenous acid phosphatase and by using combinations of ascorbic acid (AA), AA-2-phosphate and AA-2-triphosphate to provide for gradual release of AA at treated surfaces. Treatment with dips containing the AA-2-phosphates extended storage life of potato dice and pre-peeled potatoes by 5-7 days over that obtained with conventional browning inhibitor formulations but induced some leakage at cut surfaces.
[Show abstract][Hide abstract] ABSTRACT: Browning could be prevented in McIntosh apple juice by the addition of at least 200 ppm chitosan, irrespective of the chitosan product tested, followed by filtration with diatomaceous earth filter aid. Chitosan at 1000 ppm was required to prevent browning in juice from ripe Bartlett and Bosc pears. Juice from very ripe Bartlett pears did not respond to chitosan treatment. Chitosan addition interfered with the prevention of browning in apple and pear juice by centrifugation.
[Show abstract][Hide abstract] ABSTRACT: The influence of recipe and raw material on the pH of home-canned peppers was investigated. Acidification levels specified in typical recipes were compared with those found in similar commercial products having acceptable pH values. Green and red peppers representing 12 varieties were analyzed for pH, acidity, and response to acidulation in the raw state and after canning with and without added vinegar. Hungarian Wax and Sweet Cherry peppers were more highly buffered than the other cultivars analyzed, requiring the addition of 1 tbsp vinegar (5% acidity) per pint jar of canned product to reduce the pH to or below 4.6. No less than that quantity of vinegar should be added.
[Show abstract][Hide abstract] ABSTRACT: The effects of emulsifying agents (EA) on the stability of aqueous dispersions of ascorbyl palmitate (AP), laurate (AL), and decanoate (AD), and on the effectiveness of these compounds as browning inhibitors in apple juice were investigated. The stability of 1.14 mM AP, AL or AD, dispersed in simulated juice, was greatly improved by the addition of hydrophilic EA's such as Tween 60. More lipophilic EA's also were effective in stabilizing AL and AD dispersions. However, the addition of EA's to these browning inhibitors failed to improve their effectiveness in juice and, in the case of Tweens, had a detrimental effect. These results are attributed to the solubilization or activation of bound polyphenol oxidase.
[Show abstract][Hide abstract] ABSTRACT: Alternative procedures for the disposal of waste calcium bisulfite cherry processing brine were investigated. SO2 concentrations in waste brine can be reduced to several hundred ppm by neutralization with lime and filtration or sedimentation to separate precipitated CaSO3. Lower SO2 concentrations can be achieved by oxidation with H2O2. Anaerobic storage of sludge and supernatant from neutralized brine may produce objectionable odors. Brine to be disposed in deep wells should be pretreated by neutralization and sedimentation. Substitution of Ca(H2PO4)2· H2O for CaCl2 in brine formulations to eliminate chloride from processing waste was not feasible.
[Show abstract][Hide abstract] ABSTRACT: Ascorbic acid-2-phosphate (AAP) and ascorbic acid (AA) were infiltrated into apple and potato tissue to control browning. Apple tissue absorbed more AAP and AA than potato under similar conditions. AAP hydrolysis by endogenous acid phosphatase (APase) yielded AA which accumulated or became oxidized to dehydroascorbic acid, depending on the rate of hydrolysis and browning tendencies of samples. APase activity varied greatly with commodity, method of sample preparation and sample pH. Variation in the ability of AAP to inhibit browning in different products could be explained by these factors.
[Show abstract][Hide abstract] ABSTRACT: Recycling was evaluated as a means of alleviating pollution from cherry processing brines. Brines were reclaimed by filtration, treatment with activated carbon, and addition of SO2 and lime. Cherries processed with reclaimed brine were similar in composition, color, and firmness to controls. The capacity of the reclamation system was estimated. Reclaimed brine became discolored if iron exceeded 30–40 ppm. SO2 losses were higher in full strength brines than in weaker brines. Brined cherries repacked in water lost more SO2 than did brined controls and became discolored during storage. Maraschino cherries prepared from water-packed cherries were less firm than controls. Design and engineering studies based on these data are in progress.
[Show abstract][Hide abstract] ABSTRACT: SUMMARY– Explosion puffed dehydrated potatoes may develop a characteristic off-flavor during puffing. An objective method, based on the analysis of headspace vapor by GLC, was developed to measure peak heights of components associated with this off-flavor. Ground potatoes and an internal standard, ethylbutyrate, were added to boiling water, and the mixture was equilibrated for 10 min at 98°C. A vapor sample was then withdrawn and analyzed chromatographically on a Carbowax 20M packed column at 100°C using an inlet splitter. Heights of peaks corresponding to 2-methylpropanal plus acetone, 2-methylbutanal plus 3-methylbutanal, hexanal, and ethylbutyrate were determined and peak ratios calculated. The method was found to be precise, accurate, and rapid. Comparisons of a number of potato samples by sensory evaluation and the objective method showed that the intensity of the off-flavor is associated with the heights of the 2-methylpropanal plus acetone and 2-methylbutanal plus 3-methylbutanal peaks.
[Show abstract][Hide abstract] ABSTRACT: The feasibility of acidifying home canned tomatoes was determined. Citric acid, lemon juice, or vinegar were added at three concentrations to tomatoes which were canned by the raw pack method. The pH of low acid products was lowered effectively by acidulation with lg citric acid monohydrate or 1 tbsp lemon juice per pint. Vinegar was less effective than the other acidulants and also contributed an off-flavor at all levels. Acidulants equilibrated more rapidly when added to filled jars rather than to empty jars before filling. Alternative acidulation recommendations were compared by use of data derived from canning studies and from measurements of the response of high pH raw tomatoes to acidulation.
[Show abstract][Hide abstract] ABSTRACT: SUMMARY– Headspace vapor components previously associated with the intensity of an off-flavor in explosion puffed dehydrated potatoes were added to potatoes lacking the off-flavor to determine the flavor contribution of these compounds. 2-Methylpropanal produced a characteristic wet fur flavor note while 2- and 3-methylbutanal modified this flavor and contributed burnt flavor notes. While these flavor notes resembled some elements of the puffing off-flavor, the total off-flavor at its normal intensity could not be simulated by combinations of these compounds in potato at realistic concentrations. Acetone, which is also present in the headspace vapor of explosion puffed dehydrated potatoes, was found as a major headspace component of fresh boiled potatoes. This compound and smaller amounts of 2- and 3-methylbutanal were produced in overcooked fresh potatoes which lacked the puffing off-flavor.
[Show abstract][Hide abstract] ABSTRACT: The relationship between aroma and volatile composition of McIntosh apples was investigated. Significant correlations were found between aroma qualities determined organoleptically by a trained panel and by GLC. Unripe apples contained low levels of all volatiles and exhibited grassy and green aroma notes. C-6 aldehydes correlated with overall aroma intensity, ripeness, and fruity and aromatic notes. Esters correlated with a cheesy aroma note. Overripeness correlated with esters and total peaks in unstored but not in stored apples. The GLC peak groups which previously were found to correlate with physical and chemical properties related to maturity in unstored McIntosh apples also correlated with aroma.
[Show abstract][Hide abstract] ABSTRACT: Reflectance procedures were developed to measure the extent of enzymatic browning at cut surfaces and in the raw juice of apple and pear fruits. Reflectance L and a measurements, made at transversely cut surfaces of plugs bored from fruit halves, were linear or bilinear with log time and related to the extent of browning in six apple cultivars. With apple and pear juices, tristimulus values changed linearly with time in samples undergoing browning. Differences between initial and final tristimulus values were better indices of browning than the slopes of time curves. The suitability of these procedures for evaluating the effectiveness of browning inhibitors was demonstrated with SO2 and ascorbic acid treatments.
[Show abstract][Hide abstract] ABSTRACT: Novel browning inhibitors were evaluated in raw apple juice and on the cut surface of apple plugs, using quantitative measurements of color changes during storage to assess treatment effectiveness. Ascorbic acid-2-phosphate (AAP) and -triphosphate (AATP) showed promise for cut surfaces but were ineffective in juice. Ascorbic acid-6-fatty acid esters showed anti-browning activity in juice. Cinnamate and benzoate inhibited browning in juice but induced browning when applied to cut surfaces. Combinations of β-cyclodextrin with ascorbic acid (AA), AAP or ascorbyl palmitate were effective in juice but not on cut surfaces. Combinations of AA with an acidic polyphosphate were highly effective with both juice and cut surfaces.