Scale-up model of forced air-integrated gaseous chlorine dioxide for the decontamination of lowbush blueberries

Gaseous chlorine dioxide (ClO₂) is a promising sanitizer for frozen products because of its efficacy under nonthermal and waterless conditions. A major knowledge gap exists between laboratory trials and effectiveness at the industrial scale. To address this, a pilot study implementing a pallet-sized fumigation container (60 harvest totes) was designed for gaseous ClO₂. Fifty kilograms of blueberries were exposed to initial dose of 57.46 mg/L, representing a treatment of 2.35 mg/g of blueberries. Blueberries remained enclosed for 10 hr. Reduction of all viable cells, coliforms, yeasts, and molds were measured by plating treated samples on Tryptic Soy Agar, Violet Red Bile Agar, and Dichloran Rose Bengal Chloramphenicol Agar and compared to untreated controls. The results demonstrate that a significant reduction of 1.5 log CFU/g can be achieved against coliforms after ClO₂ exposure. Our findings demonstrate a cost-effective procedure that could be adapted to commercial processing.     

A simple instrument-free gaseous chlorine dioxide method for microbial decontamination of potatoes during storage

An instrument-free gaseous chlorine dioxide (ClO₂) method to control microorganisms on potatoes during storage was developed. Gaseous ClO₂ was generated by combining an equal amount of impregnated sodium chlorite and activating acids in a sachet without using any solution or equipment. After activation by mixing, the sachet was placed in the application area. The decontamination efficiency of ClO₂ on natural microbiota including total microorganisms, yeasts and molds, and inoculated Pseudomonas aeruginosa on potatoes was investigated. Different treatments using 2, 3, and 4 g of materials and various time intervals (2.5 and 5 h) to generate 16, 20, 24, 30, 32, and 40 mg/L of ClO₂ were evaluated. The results were effective for natural microbiota, showing over a 5 log CFU/potato reduction with a 4 g treatment after 5 h. For P. aeruginosa, there was almost a 6 log CFU/potato reduction after 5 h of the 4 g treatment. The lowest treatment tested (2 g at 2.5 h) showed reductions of 1.7, 1.9, and 2.3 log CFU/potato for total microorganisms, yeasts and molds, and P. aeruginosa, respectively. Gaseous ClO₂ did not affect the overall visual quality of the potato. The residue of ClO₂ decreased to <1 mg/L after 14 days for each treatment, indicating ClO₂ dissipates naturally over time.     

A pilot-scale evaluation of using gaseous chlorine dioxide for decontamination of foodborne pathogens on produce and low-moisture foods

Small-scale studies have shown that chlorine dioxide gas, ClO_2(g), was effective for decontamination of produce, nuts, and spices. This study conducted a pilot-scale evaluation to identify effective ClO_2(g) treatment parameters for commercial-scale applications. The gas was produced by a generator utilizing sodium chlorite and chlorine gas for decontamination of Shiga toxin-producing Escherichia coli (STEC), Listeria monocytogenes, and Salmonella inoculated on tomatoes, blueberries, baby-cut carrots, almonds, and peppercorns. Inoculated samples and 45 kg tomatoes in a 1,246-L treatment chamber were exposed to various ClO_2(g) concentrations (mg/L) and times 9 (hr) at 70–95% RH to determine the treatment effects on the pathogen reductions. Results showed that the treatment caused higher reductions on produce. A ClO_2(g) treatment of 1 mg/L-3 hr at 70% RH reduced 4.9–6.8, 5.1–5.6, and 4.2–6.3 log CFU/g of STEC, L. monocytogenes, and Salmonella, respectively, on produce, with the highest reductions on baby-cut carrots. For almonds and peppercorns, ClO_2(g) treatments under higher RH caused higher reductions. The treatment of 2 mg/L-9 hr or 3 mg/L-4 hr at 95% RH reduced >4.0 log of STEC and Salmonella on almonds, and 1 mg/L-5 hr at 85% RH achieved >5.0 log reductions on peppercorns. Applying moisture to the surfaces of almonds caused >4.0 log reductions using 1 mg/L-5 hr at 95% RH. This study identified effective ClO_2(g) treatment parameters for achieving >4.0 log reductions of common pathogens on tomatoes, blueberries, baby-cut carrots, almonds, and peppercorns and showed that ClO_2(g) generator is suitable for large-scale decontamination. These findings can be used for pilot-scale ClO_2(g) decontamination of these products and for testing using ClO_2(g) for commercial-scale decontamination trials.     

Gaseous chlorine dioxide technology for improving microbial safety of spices

In this study, black peppercorns and cumin seeds were inoculated with a five-serotype cocktail of Salmonella or its surrogate Enterococcus faecium NRRL B-2354. The inoculated samples (ca. 10⁷ CFU/g) were treated by ClO₂ gas at different gas concentrations (5, 10, and 15 mg/L) and relative humidities (60, 70, and 80%) at room temperature (25 °C) at five gas exposure times (60, 120, 180, 240, 300 min). More than 5-log reduction of Salmonella was achieved in both spices with 300 min of ClO₂ gas treatment at 15 mg/L and 80% RH. The corresponding values for E. faecium were 4.36 and 4.17 log CFU/g in black peppercorns and cumin seeds, respectively, which were significant lower than Salmonella (p < 0.05). Gas concentration, RH, and exposure time showed significantly positive linear associations with Salmonella inactivation. E. faecium appears a suitable surrogate for Salmonella and can be used for future process validations using comparable conditions.     

Surface pasteurization of fresh pomelo juice vesicles by gaseous chlorine dioxide

This study developed an in-package pasteurization method that released gaseous chlorine dioxide (ClO₂) triggered when moisture vapor from the fresh produce interacted with a ClO₂ precursor. The samples were placed in sealed containers (750 ml) containing mixtures (0.1–1.0 g) of sodium chlorite and citric acid powders (1:1) and treated for up to 15 min at 25°C. Our results showed that, production of gaseous ClO₂ was linearly correlated with the reaction time (R²>0.95) with mean concentrations in the range of 1.70 – 8.66 mg/L. The gaseous ClO₂ treatments for 15 min significantly reduced Escherichia coli and fungi populations on pomelo juice vesicles with reductions of 6 and 2 log CFU/g, respectively. Perchlorate and chlorite in samples were not detected, and chlorate was only detected when the mean ClO₂ concentration was over 4.09 mg/L. The treatments did not significantly affect total soluble solids, total acids, pectin and malondialdehyde contents, and color of pomelo juice vesicles. The contents of ascorbic acid, naringin, and limonin, and bitterness score decreased with the increase of mean ClO₂ concentrations. Overall, our results demonstrate an effective nonthermal approach for microbial inactivation while maintaining the quality of fresh pomelo juice vesicles.     

Antimicrobial efficacy of gaseous chlorine dioxide against Salmonella enterica Typhimurium on grape tomato (Lycopersicon esculentum)

The aim of this study was to investigate the effects of gas level and treatment condition on antimicrobial efficacy of ClO₂ gas against Salmonella enterica Typhimurium on grape tomato (Lycopersicon esculentum). Grape tomatoes were dip‐inoculated with inoculum of S. enterica Typhimurium TISTR 292 (ATCC 13311) (9.79 ± 0.39 log CFU mL^?1) and allowed to dry before treatments. The pre‐inoculated samples were exposed to 0.15–0.85 mg of ClO₂ gas, for up to 58 min. The treatments at 4 and 25 °C resulted in population reductions of S. enterica Typhimurium of up to 3.95 ± 0.22 and 7.37 ± 0.39 log CFU per fruit, respectively. The population reduction results were used to construct statistical models to predict efficacy of ClO₂ gas. The second‐order equations for treatments at 4 and 25 °C had R² of 0.87 and 0.95, respectively, and indicated that efficacy of ClO₂ gas was significantly influenced by ClO₂ gas level, exposure time and treatment temperature.     

Effects of Pseudomonas chlororaphis and gaseous chlorine dioxide on the survival of Salmonella enterica on tomatoes

Control of Salmonella enterica on tomatoes is important for food safety. The aim of this research was to evaluate the survival of Salmonella enterica serovars Montevideo (SM) and Typhimurium (ST) on tomatoes exposed to gaseous chlorine dioxide and Pseudomonas chlororaphis (Pc). Pc was applied to stem scars of tomatoes prior to inoculations with SM and ST. Tomatoes were treated with gaseous ClO₂ at 0.4 mg L^?1 for 2 and 4 h (90% R.H. 13 °C), respectively. At 4 h of ClO₂ treatment, SM and ST populations were reduced to 0.82 and <0.30 log CFU g^?1, respectively. Tomatoes treated with SM and ST had 5.42 and 5.37 log CFU g^?1 of Salmonella. Tomatoes treated with Pc + Salmonella count was 2.59 (treated) and 5.83 log CFU g^?1 (control). Salmonella survival was similar at 2 and 4 h of ClO₂ treatment. Application of ClO₂ and Pc may reduce contamination of tomatoes by Salmonella serovars.     

Quality of Atlantic Mackerel (Scomber scombrus L.) Fillets during Modified Atmosphere Storage

Sensory, physical, biochemical and microbial quality were investigated in mackerel fillets stored under CO₂ modified atmosphere packaging (MAP) at -2°C for 21 days. Packaging gas composition remained constant during storage. An experienced sensory panel found seaweedy and cucumber-like odors (raw) decreased whereas sourness corresponded with lactic acid bacteria increase. Both sensory (raw) fillet ‘yellowness’ and Hunter ‘b’ values increased. Visual (cooked) moistness and expressible fluid decreased but no difference was found in cooking losses. Small increases in total volatile base-nitrogen and trimethylamine-nitrogen paralleled aerobic plate counts; ethanol increased linearly. Coliforms, yeasts and molds were detected at < 10 CFU/g. CO₂ MAP storage at – 2°C can maintain Grade 1 shelf-life extension for ≥ 21 days     

Development of Chlorine Dioxide Releasing Film and Its Application in Decontaminating Fresh Produce

A feasibility study was conducted to develop chlorine dioxide (ClO₂)‐releasing packaging films for decontaminating fresh produce. Sodium chlorite and citric acid powder were incorporated into polylactic acid (PLA) polymer. Films made with different amounts of PLA (100 and 300 mg), percentages of reactant (5% to 60%), and ratios of sodium chlorite to citric acid (1:2 or 2:1) were prepared using a solvent casting method. The release of ClO₂ from the resultant films was activated by moisture. Increase of reactants in the films produced more ClO₂ while higher PLA content in the films resulted in less release of ClO₂. The ratio of sodium chlorite to citric acid and activation temperature (22 °C compared with 10 °C) did not affect the ClO₂ release from the films. Antimicrobial efficacy of ClO₂ released from the films was evaluated using grape tomato as a model food. The results indicate that the films were activated by moisture from tomatoes in the package and the released ClO₂ reduced Salmonella spp. and Escherichia coli O157:H7 inoculated on the tomatoes to undetectable levels (<5 colony forming units (CFU)/tomato), achieving more than 3 log reduction. The film‐treated tomatoes did not show significant changes in color and texture as compared to controls during storage at 10 °C for 21 d. This study demonstrated the technical feasibility for development of gaseous ClO₂‐releasing packaging system to enhance microbial safety and extend shelf life of fresh produce.     

Effects of plasma-activated water on microbial growth and storage quality of fresh-cut apple

Fresh-cut ‘Fuji’ apples were immersed for 5 min in plasma-activated water (PAW) generated, by plasma generated with sinusoidal voltages at 7.0 kHz with amplitudes of 6 kV, 8 kV, and 10 kV, designated PAW-6, PAW-8, and PAW-10, respectively. The control group was soaked in distilled water for 5 min instead of PAW. The results indicated that the growth of bacteria, molds, and yeasts was inhibited by PAW treatments during storage at 4 ± 1 °C, especially the microbial inactivation with PAW-8, which was the most efficient. PAW-8 reduced the microbial counts by 1.05 log₁₀CFU g⁻¹, 0.64 log₁₀CFU g⁻¹, 1.04 log₁₀CFU g⁻¹ and 0.86 log₁₀CFU g⁻¹ for aerobic bacteria (aerobic plate counts), molds, yeasts and coliforms on day 12, respectively. In addition, the bacterial counts of fresh-cut apples treated with PAW were <5 log₁₀CFU g⁻¹, which did not exceed to the existing China Shanghai local standard (DB 31/2012–2013) during 12 days of storage. PAW treatments reduced superficial browning of fresh-cut apples without affecting their firmness and titratable acidity. In addition, no significant change was observed in antioxidant content and radical scavenging activity between the PAW-treated and control groups. It is suggested that PAW is a promising method for preservation of fresh-cut fruits and vegetables, which is usually beneficial to the quality maintenance of fresh-cut fruits and vegetables during storage.     

Microbiological Evaluation of Navy Bean Protein Concentrate and Its Blend With Retail Ground Beef

A protein concentrate (NPC), obtained by alkali extraction of navy beans, was used as a model medium for microbial growth. Only three among eight bacterial cultures (Pediococcus spp, Pseudomonas spp and Streptococcus spp) grew better on mediums with NPC than on the control nutrient broth. Retail ground beef with and without 5%, 10%, and 15% NPC was wrapped with plastic film and stored up to 6 days at 4°C. Aerobic plate count, psychrophiles, coliforms, yeasts and molds were determined at 0, 3, and 6 days. All levels of NPC added to ground beef had a significant influence on aerobic plate count and coliforms. Growth of psychrophiles and yeasts and molds was not affected by NPC. Lactobacillus spp was a dominant part of the microflora of all samples.     

Shelf Life of Vacuum- or Nitrogen-Packed Pastrami: Effects of Packaging Atmospheres, Temperature and Duration of Storage on Microflora Changes

Numbers of lactobacilli, psychrotrophs and anaerobes in either vacuum- or nitrogen-packed pastrami increased significantly as storage temperature was increased above -4°C or duration extended beyond 7 days at 0, 3 and 7°C. Few significant differences observed in their numbers were attributed to types of packaging but numbers of yeasts and molds decreased significantly in nitrogen-packed samples, particularly at 7°C. Growth of coliforms to log 4.5 per gram occurred at 7°C in both packaging treatments. The initial psychrotrophs consisted of Brochothrix (51–54%), Lactobacillus (40–42%) and Pseudomonas spp. (6.6–9.0%) but Lactobacillus spp. represented 80–92% at 49 days.     

Microbial decontamination of black peppercorns by simultaneous treatment with cold plasma and ultraviolet C

An intervention technology employing simultaneous ultraviolet (UV)-C and cold plasma (CP) treatments was developed to inactivate indigenous mesophilic aerobic bacteria in black peppercorns. At higher UV intensity of UV-CP treatment and water activity of black peppercorns, microbial inactivation levels increased up to 0.6 and 1.7 log CFU/g, respectively. Using a response surface analysis, optimum CP voltage and treatment time for inactivating indigenous bacteria in black peppercorns by UV-CP treatment were predicted to be 10.3 kV and 22.1 min, respectively; these inactivated indigenous bacteria and Bacillus tequilensis spores by 3.4 log CFU/g and 1.7 log spores/g, respectively, with minimal increase in temperature (4.5 ± 1.2 °C). The bacterial inactivation rate (3.4 log CFU/g) achieved by UV-CP treatment was higher than the sum (2.7 log CFU/g) of the inactivation rates of individual UV and CP treatments. UV-CP treatment did not alter the color of black peppercorns and shows potential for application in non-thermal microbial decontamination of black peppercorns.Industrial relevanceThis study has developed a novel system for non-thermal microbial inactivation in black peppercorns using simultaneous UV-C and CP treatment (UV-CP treatment). UV-CP treatment was effective in inactivating indigenous bacteria in black peppercorns, including Bacillus tequilensis spores, and had an additive effect on microbial inactivation. The efficacy of treatment in microbial inactivation increased with higher water activity of black peppercorns. The bacterial inactivation efficacy was also influenced by the UV intensity and treatment time. The results of this study demonstrated that UV-CP treatment has the potential to be employed as a non-thermal technology to disinfect black peppercorns and possibly other spices, without affecting their color.     

Evaluation of chlorine dioxide gas release rates from dry precursors intended for applied technologies under disparate conditions and their effects on Salmonella enterica,Escherichia coli O157:H7, and Listeria monocytogenes

The diverse food safety issues facing developed countries require innovations to current food safety intervention technologies and chemistries. Several innovations have been made to highly efficacious treatments, such as chlorine dioxide (ClO₂). However, many of the innovations stop short of evaluating actual yield, practical feasibility, or basic chemistry of the technology. In this study, our aim was to evaluate ClO₂ precursors, sodium chlorite and citric acid, under disparate but applicable conditions. First, we modeled production of ClO₂ from the powdered precursors with three different masses, sample ID 1, 2, and 3, at room (18 °C) and refrigeration (2 °C) temperatures. Second, we investigated the effects of a water reservoir on ClO₂ production. Third, we assessed collection method issues that may impact reported ClO₂ values. Finally, we evaluated the precursor's efficacy against three common foodborne pathogens: Salmonella spp., Escherichia coli O157:H7, and Listeria monocytogenes on a glass surface between 15- to 60-min treatment times. Over 25 h the precursors produced between 1.87- to 37.76- and 0.87- to 4.19-mg ClO₂ under 18 and 2 °C, respectively, demonstrating that low temperatures reduced ClO₂ reported yield. Peak rates of production at 18 °C were estimated to be 3.51 mg/h, 3.83 mg/h, and 4.78 mg/h for sample ID 1, 2, and 3, respectively. Modeling the rate of production indicated that sample IDs had significantly (p < 0.0065) different rates of production, with sample ID 1 having the quickest production rate. Under 2 °C, these rates were <1 mg/h of all masses tested and did not follow the same production pattern observed at 18 °C. Under controlled conditions, availability of a water reservoir significantly increased ClO₂ production by >15 fold. We also determined that the reservoir placement could affect reported ClO₂ concentrations. At the same time, ClO₂ was able to reduce all three pathogens in <45 min by >6-log₁₀ CFU/carrier and performed significantly better at refrigeration temperature compared to room temperature.     

Efficacy of chlorine dioxide gas as a sanitizer for tanks used for aseptic juice storage

An aseptic tank model system was used to study the efficacy of chlorine dioxide (ClO₂) gas as a potential sanitizing agent for commercial epoxy-lined juice storage tanks. Selected spoilage micro-organisms (Lactobacillus buchneri, Leuconostoc mesenteroides, Eurotiumspp.,Penicilliumspp,Candidaspp. andSaccharomyces cerevisiae) were surface inoculated on to epoxy-coated stainless steel strips, placed in the model tank and subjected to different ClO₂gas treatments. The varied treatment conditions consisted of 2–14 mg l⁻¹ClO₂gas, 50–98% relative humidity, 5–120 min exposure time, and temperatures ranging from 9–31°C.L. buchneriwas used as the target micro-organism and was found to be most resistant to selected ClO₂gas treatments, followed byL. mesenteroides, followed by the yeasts and molds studied. Inactivation ofL. buchneriandL. mesenteroidesincreased with greater concentration of ClO₂gas, higher holding temperature, higher relative humidity, and more exposure time. Under the conditions of this study, all the selected micro-organisms could be completely inactivated, resulting in a sterilized surface. The recommended treatments for assuring sterility were 10 mg l⁻¹ClO₂gas for an exposure time of 30 min coupled with (a) high relative humidity (>90%) and holding temperatures between 9 and 28°C, or (b) high holding temperatures (25–28°C) and relative humidity above 69%.     

Inactivation of Bacillus cereus Spores on Red Chili Peppers Using a Combined Treatment of Aqueous Chlorine Dioxide and Hot‐Air Drying

The effect of a combined treatment using aqueous chlorine dioxide (ClO₂) and hot‐air drying to inactivate Bacillus cereus spores on red chili peppers was evaluated. Ten washed and dried pepper samples, each comprising half of a single pepper (Capsicum annuum L.), were inoculated with B. cereus spore suspension. The inoculated samples were washed with sodium hypochlorite (NaOCl; 50, 100, or 200 μg/mL) or ClO₂ (50, 100, or 200 μg/mL) solution for 1 min and then air‐dried (25 ± 1 °C, 47 ± 1% relative humidity), which was followed by drying with hot air at 55 °C for up to 48 h. The spore populations on the samples were enumerated and their a_w and chromaticity values were measured. The spore numbers immediately after treatment with NaOCl and ClO₂ were not significantly different. A more rapid reduction in spore numbers was observed in the samples treated with ClO₂ than those treated with NaOCl during drying. A combined treatment of ClO₂ and hot‐air drying significantly reduced the spore populations to below the detection limit (1.7 log CFU/sample). B. cereus spores on chili peppers were successfully inactivated by washing with ClO₂ solution followed by hot‐air drying whereas the pepper color was maintained.     

Combined effects of chlorine dioxide, drying, and dry heat treatments in inactivating microorganisms on radish seeds

We determined the combined effectiveness of ClO₂ (200 and 500 μg/ml, 5 min), air drying [25 °C, 40% relative humidity (RH), 2 h], and mild dry heat (55 °C, 23% RH, up to 48 h) treatments in killing total aerobic bacteria (TAB), Escherichia coli O157:H7, and molds and yeasts (MY) on radish seeds. A 5.1-log reduction in the number of TAB was achieved on radish seeds treated with 200 or 500 μg/ml ClO₂ followed by air drying for 2 h and dry heat treatment for 48 h or 24 h, respectively. When radish seeds were treated with 200 and 500 μg/ml ClO₂, air dried, and heat treated for 12 h and 6 h, respectively, the initial population of E. coli O157:H7 (5.6 log CFU/g) on seeds was reduced to an undetectable level (<0.8 log CFU/g). However, the pathogen was detected in 5-day-old sprouts. The reduction of MY (1.2-1.0 log CFU/g) on radish seeds under similar experimental conditions was not changed significantly during subsequent heat treatment up to 48 h. Results show that treating radish seeds with 500 μg/ml ClO₂, followed by air dried at 25 °C for 2 h and heat treatment at 55 °C for 36 h achieved a >5-log CFU/g reduction of TAB and E. coli O157:H7. These observations will be useful when developing effective strategies and practices to enhance the microbiological safety of radish sprouts.     

Quality of chilled ready-to-bake pizza stored in air and under modified atmospheres: Microbiological and sensory attributes

Modified atmosphere packaging (MAP) studies on microbiological and sensory analysis were conducted to extend the shelf life of ready-to-bake pizza stored at 7±1°C. The gas combinations used were: atm1: air (control), atm2: CO₂ (100%), atm3: N₂ (100%), atm4: 50% CO₂/50% N₂. Total plate count (TPC), yeasts/molds (Y/M), coliforms, lactic acid bacteria (LAB), psychrotrophs, and anaerobic spore formers were estimated at time intervals of 0, 5, 10, 15, and 20 days. TPC and LAB of pizza samples (atm1) reached 7.10 and 8.14 log CFU/g after 10 days of storage, respectively. Coliforms, psychrotrophs, and Y/M were significantly higher (p<0.05) for pizza samples stored in atm1 than other storage conditions of MAP. Finally, counts of anaerobic spore formers were low (<3 log CFU/g) irrespective of the packaging conditions throughout the entire storage period. It was concluded that among the 4 atmospheres examined, atm2 (100% CO₂) was the best, followed by atm4>atm3>atm1 respectively, in descending order. MAP conditions under this study may extend shelf life of pizza to considerable amount of time.     

Physiology and Microbiological Quality of Fresh-cut Mango Cubes as Affected by High-O2 Controlled Atmospheres

Preliminary study showed that among 40‐ to 100‐kPa O₂ atmospheres, 60‐kPa O₂ reduced the respiration of fresh‐cut ‘Carabao’ mango cubes the most when held at 5 °C or 13 °C for 42 h. Therefore, the effects of 60‐kPa O₂ on the physiology and microbial quality of fresh‐cut ‘Carabao’ and ‘Nam Dokmai’ mango cubes were determined and compared with those held in air. The high‐O₂ atmosphere reduced the respiration rate of ‘Carabao’ mango cubes stored at 5 °C but stimulated the rate after 2 d of storage at 13 °C. Browning of ‘Carabao’ cubes was accelerated by 60‐kPa O₂ at 13 °C. With ‘Nam Dokmai’ cubes, the high O₂ had no effect on respiration rate, browning, and incidence of water‐soaked appearance at 5 °C and 13 °C. The high O₂ did not affect texture or ascorbic acid content of ‘Carabao’ and ‘Nam Dokmai’ mango cubes at either temperature. Counts of lactic acid bacteria and molds were below the detection level (2.4 log colony‐forming units [CFU]/g) during storage at both temperatures. However, 60‐kPa O₂ stimulated the growth of mesophilic aerobic bacteria on ‘Carabao’ cubes and yeasts of ‘Nam Dokmai’ cubes at 13 °C. The increased microbial count may have been due to the higher pH of cubes stored in 60‐kPa O₂ at 13 °C than at 5 °C or in air. Within ‘Nam Dokmai’ mango cubes, the predominant genera in mesophilic aerobic bacteria were Enterobacter, Klebsiella, and Pantoea and in the yeasts were Candida, Cryptococcus, and Rhodotorula. These results indicate that 60‐kPa O₂ is not desirable for mango cubes when held at 13 °C.     

Aciduric and Heat Resistant Microorganisms in Apple Juice and Cider Processing Operations

Site visits to 15 apple juice or cider facilities were conducted in New York State. Washed apples, pulp, press juice, final product, and other samples, when appropriate, were sampled aseptically. Samples were plated on acidified potato dextrose agar, before and after heating at 70°C for 1-2 hr. For unheated samples, molds predominated in fruit, yeasts and molds in pulp, and yeasts in press and final juice samples. Average counts were 2.8 × 10⁴, 7.3 × 10⁴, 1.7 × 10⁵, and 1.4 × 10⁵/g, respectively. Heat resistant yeasts, molds, and bacteria were isolated frequently, generally at a level of less than 1 per log.