Characterization of Apples and Apple Cider Produced by a Guelph Area Orchard

Thermal stability of food-borne pathogens in apple cider is influenced by the composition of the product. As a preliminary step to determine the effect of pasteurization of apple cider on the survival of Escherichia coli O157:H7, a study was carried out to characterize apples and unpasteurized apple cider produced by a Guelph area orchard. Samples of commercial unpasteurized cider and the constituent apples were collected over 13 wk from August to November 1998, and unpasteurized laboratory cider was made from the individual apple varieties. pH, titratable acidity, turbidity, total microbial counts, total solids and °Brix for filtered and unfiltered samples were measured. The maximum, minimum, and average values for all unpasteurized commercial cider samples were found as follows: pH, 3.71, 3.17, and 3.43; titratable acidity, 93.47, 49.46, and 69.95 mL of 0.1 N NaOH/100 mL; total solids, 13.21, 10.93, and 11.90%; °Brix, 13.01, 11.17, and 12.02; turbidity, 238.1, 145.1, and 204.9 nephelometric turbidity units; and total plate count, 4.91, 2.61, 3.75 log cfu/mL. There were no significant differences (P>0.05) between filtered and unfiltered samples. In addition, in commercial unpasteurized cider, there were no significant differences (P>0.05) with respect to any of the factors with the time of processing. The composition of the unpasteurized laboratory cider made from individual apple varieties was dependent on the variety, but was generally within the ranges from the published literature values. McIntosh apples showed a significant (P\le0.05) decrease in titratable acidity with time of harvest. The results suggest that it is necessary to take the composition of commercial apple cider into account when developing thermal inactivation models for food-borne pathogens.     

Potential sources of microbial contamination in unpasteurized apple cider

A study was conducted to identify possible sources of microbial contamination and to assess the effect of good cleaning and sanitation practices on the microbial quality and safety of unpasteurized apple cider. Raw unwashed apples, washed apples, cleaning water, fresh cider, and finished cider samples were collected from five Ontario producers over 4 months and microbiologically tested. Total coliforms were found in 31, 71 and 38% of the unwashed apple, water, and washed apple samples, respectively. Escherichia coli was found in 40% of the water samples from one producer alone. The washing step was identified as a potential source of contamination, possibly due to water in the dump tanks seldom being refreshed, and because scrubbers, spray nozzles, and conveyors were not properly cleaned and sanitized. Higher total coliform counts (P < 0.0001) and prevalence (P < 0.0001) in fresh cider compared with those in unwashed apples and washed apples indicated considerable microbial buildup along the process, possibly explained by the lack of appropriate equipment sanitation procedures. Results showed that producers who had better sanitary practices in place had lower (P < 0.001) total coliform prevalence than the rest of the producers. Overall results show that good sanitation procedures are associated with improved microbial quality of fresh cider in terms of total coliforms and that operators who pasteurize and/or UV treat their product should still be required to have a sound good manufacturing practices program in place to prevent recontamination. Cryptosporidium parvum, an important pathogen for this industry, was found in different sample types, including washed apples, water, and fresh and finished cider.     

Influence of fruit variety, harvest technique, quality sorting, and storage on the native microflora of unpasteurized apple cider

Apple variety, harvest, quality sorting, and storage practices were assessed to determine their impact on the microflora of unpasteurized cider. Seven apple varieties were harvested from the tree or the ground. The apples were used fresh or were stored at 0 to 4 degrees C for < or = 5 months and were pressed with or without quality selection. Cider yield, pH, Brix value, and titratable acidity were measured. Apples, postpressing apple pomace, and cider samples were analyzed for aerobic bacteria, yeasts, and molds. Aerobic bacterial plate counts (APCs) of ciders from fresh ground-picked apples (4.89 log CFU/ml) were higher than those of ciders made from fresh, tree-picked apples (3.45 log CFU/ml). Quality sorting further reduced the average APC to 2.88 log CFU/ml. Differences among all three treatment groups were significant (P < 0.0001). Apple and pomace microbial concentrations revealed harvest and postharvest treatment-dependent differences similar to those found in cider. There were significant differences in APC among apple varieties (P = 0.0001). Lower counts were associated with varieties exhibiting higher Brix values and higher titratable acidity. Differences in APC for stored and fresh apples used for cider production were not significant (P > 0.05). Yeast and mold counts revealed relationships similar to those for APCs. The relationship between initial microbial load found on incoming fruit and final cider microbial population was curvilinear, with the weakest correlations for the lowest apple microflora concentrations. The lack of linearity suggests that processing equipment contributed to cider contamination. Tree-picked quality fruit should be used for unpasteurized cider production, and careful manufacturing practices at cider plants can impact both safety and quality of the final product.     

Inactivation of different strains of Escherichia coli O157:H7 in various apple ciders treated with dimethyl dicarbonate (DMDC) and sulfur dioxide (SO2) as an alternative method

Escherichia coli has been identified as the causative agent in numerous foodborne illness outbreaks associated with the consumption of fresh apple cider. Apple cider has a pH which is normally below 4.0 and would not be considered a medium capable of supporting the growth of foodborne pathogens. The association of unpasteurized apple cider with foodborne illness due to E. coli O157:H7 has however, led to increased interest in potential alternative methods to produce pathogen free cider. Apple cider was prepared from eight different apple cultivars, inoculated with approximately 10⁶–10⁷ CFU of three strains of E. coli O157:H7 per ml (933, ATCC 43889, and ATCC 43895) and tested to determine the effectiveness of sulfur dioxide (SO₂) and dimethyl dicarbonate (DMDC). Bacterial populations for treated and untreated samples were then enumerated by using non-selective media. Eight different ciders were treated with DMDC (125 and 250 ppm) and SO₂ (25, 50, 75, 100 ppm). Greater than a 5-log reduction was achieved at room temperature with 250 ppm of DMDC and 50 ppm of SO₂ after the incubation time of 6 h and 24 h, respectively. Addition of DMDC and/or SO₂ may offer an inexpensive alternative to thermal pasteurization for the production of safe apple cider for small apple cider producers.     

UV INACTIVATION OF E. COLI O157:H7 IN APPLE CIDER: QUALITY, SENSORY AND SHELF-LIFE ANALYSIS

Increasing concern about food safety following contamination of unpasteurized apple cider with Escherichia coli O157:H7 reinforces the need for using the best technologies in apple cider production. Pasteurization of apple cider with ultraviolet irradiation (UV) is a low‐cost alternative to heat pasteurization for small processing operations. UV treatment efficacy applied to raw unpasteurized apple cider was examined through evaluation of physical parameters, exposure time and treatment dosage. A UV light processing system was used to treat apple cider. The apple cider received a calculated average dosage of 8777 µW‐s/cm ² per pass through the system. UV light (at 254.7 nm) was effective in reducing bacteria‐inoculated apple cider by an average of 2.20 logs per pass. In multiple passes, the 5‐log reduction mandated by the Food and Drug Administration was achieved. Sensory analysis yielded no significant differences between the UV‐treated and control apple ciders. Experiments with UV‐treated apple cider indicated a significant extension of product shelf life through inhibition of yeast and mold growth. For low throughput apple cider processing operations, this technology is a viable cost‐effective alternative.     

Influence of Simulated Apple Cider Composition on the Heat Resistance of Escherichia coli O157:H7

In light of recent outbreaks involving Escherichia coli O157:H7 in unpasteurized apple cider, this study was undertaken to determine the effect of apple cider composition on the heat resistance of this pathogen, and to develop regression models to predict its inactivation under varying conditions of pH (2.82-4.06), titratable acidity (TA) (31.14-111.80), and Brix (8.86-15.32). Heating was conducted in capillary tubes submerged in a stirred oil bath, and viability was determined by plating on tryptic soy agar. A central rotatable composite design was used which consisted of 18 treatment combinations at each of three heating temperatures (52, 54 and 56°C). The time (min) for a 2-log reduction (cT_2D) and a 4-log reduction (T_4D) were calculated for each of the 54 treatment combinations by fitting a smoothing spline to the survival curve. Two regression models were developed to predict the effect of the factors on T_2D andT_4D , and regression coefficients of 0.95 and 0.90 were obtained, respectively. The effects of pH and TA on T_2D and T_4D were significant (P\le0.05) at all heating temperatures. Increasing Brix to 15 ° had a protective effect on E. coliO157:H7. The interaction between pH and TA was significant, as was the combined effect of Brix and pH. The combination of Brix and TA was not significant. The results support the use of a nonparametric model such as a smoothing spline for the analysis of survival curves when parametric models are not adequate.     

Verifying apple cider plant sanitation and hazard analysis critical control point programs: choice of indicator bacteria and testing methods.

The objectives of this study were (i) to evaluate the survival of coliforms, Escherichia coli, and enterococci in refrigerated apple cider; (ii) to develop simple and inexpensive presumptive methods for detection of these bacteria; (iii) to perform a field survey to determine the prevalence of these bacteria on apples and in apple cider; and (iv) based on our results, to recommend the most useful of these three indicator groups for use in verifying apple cider processing plant sanitation and hazard analysis critical control point (HACCP) programs. Eight of 10 coliform strains (5 E. coli, 1 Enterobacter aerogenes, and 2 Klebsiella spp.) inoculated into preservative-free apple cider (pH 3.4, 13.3(o) Brix) survived well at 4 degrees C for 6 days (< or = 3.0 log10 CFU/ml decrease). Of 21 enterococci strains (Enterococcus faecalis, E. faecium, and E. durans), only 2 E. durans and 3 E. faecium strains survived well. Simple broth-based colorimetric methods were developed that detected the presence of approximately 10 cells of coliforms or enterococci. In three field studies, samples of unwashed apples (drops and picked), washed apples, and freshly pressed cider were presumptively analyzed for total coliforms, E. coli, and enterococci using qualitative and/or quantitative methods. Drop apples were more likely than picked apples to be contaminated with E. coli (26.7% vs. 0%) and enterococci (20% vs. 0%). Washing had little effect on coliform populations and in one field study was associated with increased numbers. Total coliform populations in cider ranged from < 1 CFU/ml to > 738 most probable number/ml, depending on the enumeration method used and the sample origin. E. coli was not recovered from washed apples or cider, but enterococci were present on 13% of washed apple samples. The qualitative coliform method successfully detected these bacteria on apples and in cider. Based on its exclusively fecal origin, good survival in apple cider, and association with drop apples, we conclude that E. coli is the most useful organism for verifying apple cider sanitation and HACCP programs.     

Impact of apple processing modes on extracted juice quality: Pressing assisted by pulsed electric fields

The purpose of this study was to compare the effects of pulsed electric field (PEF) on apple juice characteristics (turbidity, polyphenolic content and antioxidant capacities). The pressing was used as a standard method for juice extraction. Experiments were carried out at a constant pressure (P = 3 bar) using a laboratory press cell. Two different methods for PEF application at 400 V/cm were investigated (PEF treatment of whole samples before cutting and PEF treatment of apple slices after cutting). PEF treatment resulted in increase of the juice yield from 44 g/100 g apple (untreated samples) to 58 g/100 g apple (treatment of whole apples) and 64 g/100 g apple (treatment of slices) after 30 min of pressing. The analysis of pH and conductivity showed no significant difference between untreated and PEF-treated samples. However, the total soluble matter content of juice increased after PEF treatment. The obtained turbidity and transmittance data evidence a noticeable improvement of juice clarity for PEF-treated samples. The PEF pre-treatment was accompanied by an increase of the content of polyphenols and intensification of the antioxidant capacities of juice. Most of these effects (juice clarity and content of antioxidants) were more pronounced for the whole treated apples as compared to untreated apples and PEF-treated apple slices. The evolution of apple browning before and after PEF treatment was more pronounced for whole samples. PEF treatment accelerates browning. The obtained data can contribute to the determination of an optimum time for PEF application. The results evidence that PEF-enhanced expression is promising for production of higher quality juices. PEF treatment of whole apples reduces the energy consumption and is advantageous for industrial applications as compared to the treatment of apple slices. PEF combined with pressing can become a good alternative to traditional process.     

Characterisation of Asturian cider apples on the basis of their aromatic profile by high-speed gas chromatography and solid-phase microextraction

Headspace solid-phase microextraction (SPME) coupled to high-speed gas chromatography with FID detector (HSGC-FID) and with quadrupole mass spectrometric detector (GC–MS) was employed to study the volatile compounds in Asturian cider apples. The optimised conditions used for characterisation of cider apple were: sample equilibration at 25 °C for 12 h, followed by PDMS–DVB fibre exposure to the headspace above the sample for 5 min and finally thermal desorption of the adsorbed substances in the injector port for GC analysis. The use of high-speed gas chromatography allowed the separation of 27 compounds in less than 8 min, reducing the analysis time in 80% compared to conventional gas chromatography. A simple, rapid and reliable method to analyze volatile compounds in cider apples has been developed. The aromatic profile of 59 apple samples included in eight apple varieties was analysed. The different apples were obtained from two consecutive harvests (2005 and 2006). The apples volatile compounds together with chemometric techniques such as principal components analysis (PCA), Bayesian analysis and linear discriminant analysis (LDA), allowed us to differentiate apples on the basis of the sweet or sharp category to which the cider apple variety belongs. Volatile compounds such as ethyl heptanoate, E-farnesene, ethyl butyrate and hexyl caprylate are closely related to cider apple cultivars of the sweet category, while propyl butyrate and butyl acetate are related to the sharp class.     

Polyphenol profiles of apple juices

Focusing on 17 constituents, the polyphenol profiles of juices freshly made from various dessert (n = 4) and cider apple cultivars (n = 7) as well as commercially available apple juices (n = 24) were investigated using high-performance liquid chromatography-photodiode array detection (HPLC-DAD) and (HPLC)-electrospray ionization-tandem mass spectrometry (ESI(neg)-MS/MS) analyses. Significant differences in the total polyphenol content as well as the profiles of the apple cultivars under study were observed. For dessert apples the total polyphenol content ranged from 154 to 178 mg/L, whereas for 'old' German cider apple cultivars 261-970 mg/L were determined. Boskoop showed the highest (970 mg/L) and Granny Smith the lowest (154 mg/L) polyphenol content of the freshly prepared samples under study. Hydroxycinnamic acids, with chlorogenic acid as dominating constituent, ranged from 57 to 68 mg/L as well as from 134-593 mg/L in juices made from dessert apples and that from cider apples, respectively. Dessert apple juices showed lower contents of dihydrochalcones (10-35 mg/L) and flavan-3-ols (50-95 mg/L) compared to that of cider apples (34-171 mg/L and 70-393 mg/L, respectively). Quercetin and its derivatives were found from 0.4-4 mg/L and 0.4-27 mg/L in juices made from dessert apples and that of cider apples, respectively. Compared with freshly made juices, lower contents of polyphenols were determined in the commercial samples under study. Amounts ranging from 110-459 mg/L, dominated by chlorogenic acid with concentrations from 53-217 mg/L, were determined. Information about cultivar-typical apple polyphenol content and profile is important for bioactivity studies and, consequently, essential for the development of consumer-relevant products with particular nutritional functionalities.     

Brewing of glucuronic acid-enriched apple cider with enhanced antioxidant activities through the co-fermentation of yeast (Saccharomyces cerevisiae and Pichia kudriavzevii) and bacteria (Lactobacillus plantarum)

Co-fermentation using yeast (Saccharomyces cerevisiae and Pichia kudriavzevii) and the bacteria (Lactobacillus plantarum) as starters isolated from spontaneous sourdough was conducted for the brewing of glucuronic acid (GlcA)-enriched apple cider. The concentration of GlcA in the apple cider co-fermented for 14 d with commercial S. cerevisiae and L. plantarum was 37.7 ± 1.7 mg/mL while a concentration of 62.8 ± 3.1 mg/mL was recorded for fermentation with P. kudriavzevii and L. plantarum, which was higher than the corresponding single yeast fermentation. The co-fermented apple cider revealed higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of 171.67 ± 0.79 µg trolox equivalents (TE)/mL using P. kudriavzevii and L. plantarum, compared to the control (143.89 ± 7.07 µg TE/mL) just using S. cerevisiae. Thus, the co-fermentation of S. cerevisiae and L. plantarum and P. kudriavzevii and L. plantarum provided a new strategy for the development of GlcA-enriched apple cider with enhanced antioxidant capacity.     

苹果酒中酚酸、黄烷-3-醇的检测

以小国光(Ralls)和富士(Fuji)及其所酿制的新鲜苹果酒为试验材料,采用反相高效液相色谱法测定分析苹果原汁、发酵中酒样和苹果成品酒中11种酚酸、5种黄烷-3-醇的含量。结果表明:苹果和苹果酒中存在4种酚酸(原儿茶酸、绿原酸、咖啡酸、对-香豆酸)、2种黄烷-3-醇(儿茶素和表儿茶素);不同品种的苹果原汁和苹果成品酒中酚类物质的含量都存在显著差异。其中,小国光苹果和小国光苹果酒中的酚类物质总含量较高;对于每个品种,绿原酸都是最主要的酚酸类物质,含量最高的黄烷-3-醇类物质都是表儿茶素。随着发酵过程的进行,苹果酒中酚类物质的含量有不同程度的增加。其增加趋势为S型曲线,即先平缓再较快再平缓。     

Microwave heating of apple mash to improve juice yield and quality

The effects of four heat treatments of apple mash on juice yield and quality were evaluated and compared to juice produced from unheated apple mash at 21°C. Fuji and McIntosh apple mashes were heated to bulk temperatures of 40°C, 50°C, 60°C and 70°C in a 2450 MHz microwave oven at 1500 W. Juice yield increased when mash was heated before pressing. Cider produced from the heated mashes had comparable pH, titratable acidity, and sensory characteristics to cider produced from room temperature mashes; however, total phenolic and flavonoid content of the juice increased with increasing mash temperature. Soluble solids and turbidity also increased as treatment temperature increased.     

Nonthermal inactivation and sublethal injury of Lactobacillus plantarum in apple cider by a pilot plant scale continuous supercritical carbon dioxide system

The objective of this study was to evaluate the efficacy of supercritical carbon dioxide (SCCO₂) for inactivating Lactobacillus plantarum in apple cider using a continuous system with a gas-liquid metal contactor. Pasteurized apple cider without preservatives was inoculated with L. plantarum and processed using a SCCO₂ system at a CO₂ concentration range of 0-12% (g CO₂/100 g product), outlet temperatures of 34, 38, and 42 °C, a system pressure of 7.6 MPa, and a flow rate of 1 L/min. Processing with SCCO₂ significantly (P < 0.05) enhanced inactivation of L. plantarum in apple cider, resulting in a 5 log reduction with 8% CO₂ at 42 °C. The response surface model indicated that both CO₂ concentration and temperature contributed to the microbial inactivation. The extent of sublethal injury in surviving cells in processed apple cider increased as CO₂ concentration and processing temperature increased, however the percent injury dramatically decreased during SCCO₂ processing at 42 °C. Structural damage in cell membranes after SCCO₂ processing was observed by SEM. Refrigeration (4 °C) after SCCO₂ processing effectively inhibited the re-growth of surviving L. plantarum during storage for 28 days. Thus this study suggests that SCCO₂ processing is effective in eliminating L. plantarum and could be applicable for nonthermal pasteurization of apple cider.     

Effect of mash maceration and ripening stage of apples on phenolic compounds and antioxidant power of cloudy juices: A study using chemometrics

The effects of different enzymatic preparations on total phenolic content, phenolic profile (HPLC), and ferric reducing antioxidant power (FRAP) of cloudy juices from Lis Gala and Fuji Suprema apples varieties, at three ripening stages (unripe, ripe and senescent) were investigated using Principal Component Analysis and Hierarchical Cluster Analysis. The commercial preparations enzymatic (Ultrazym^® AFPL; Pectinex^® Ultra Clear; Pectinex^® SMASH XXL; Panzym^® YieldMASH) increased the total phenolic compounds and ferric reducing capacity of the cloudy juice from unripe and ripe Lis Gala (respectively by 67 and 49% for unripe apples, and 28 and 33% for ripe apples) and unripe Fuji Suprema apples (23 and 55%), while for the ripe Fuji Suprema apples only Pectinex^® Ultra Clear and Panzym^® YieldMASH had this effect. No significant (p > 0.05) was observed on senescent stage, whatever the enzymatic preparation. Enzymatic preparations could increase phenolic compounds concentration and antioxidant capacity of cloudy apple juice, but this effect depended on the maturity of the apples.     

Effect of processing treatments on the characteristics of juices and still ciders from Ontario‐grown apples

Recent interest in the commercial production of cider in Ontario, Canada revealed a lack of information on cider prepared from apples grown in North America. A study was conducted using locally grown culinary and dessert varieties of apples, since there is a lack of true cider varieties grown in Ontario. Four processing methods (treatments) were evaluated with respect to their effect on juice and cider characteristics; the chemical and microbiological characteristics of the juices and still ciders are reported. Sulphite addition to the juice at the time of juice extraction had no effect on the characteristics evaluated. Storage of fruits at 13 °C until they showed signs of shrivelling or senescence decreased juice yield and affected titratable acidity and pH levels of juices and ciders. Freezing fresh apples and thawing prior to processing produced juices that did not undergo keeving and had higher mould and yeast populations; methanol was present in juices and ciders from thawed apples. The significant effects of storage and freezing on apple juice characteristics should be taken into account when considering a delay in the processing of apples for cider production. © 2003 Society of Chemical Industry     

STORAGE QUALITY OF PASTEURIZED AND UV TREATED APPLE CIDER

Two studies were conducted to assess the effect of hot-fill pasteurization at 63C and UV irradiation at 14 mJ/cm² on the quality and shelf-life of apple cider packaged under controlled conditions with minimal packaging contamination, and under pilot plant conditions resembling commercial operations. The processed cider was stored at 7C for up to 14 weeks in the first study and 4 weeks in the second. Microbiological, chemical and sensory tests were conducted weekly on cider samples. There were no significant differences among the fresh processed ciders with regard to taste and preference. All treatments achieved a reasonable reduction in microbial counts, although hot-fill pasteurization provided longer shelf-life. There were significant changes in pH, titratable acidity, soluble solids and turbidity of samples during storage. Hot-fill at 63C is a comparable alternative to flash pasteurization at 71C for 6 s for the production of safe quality cider at small cider mills.     

Evaluation of wash treatments for survival of foodborne pathogens and maintenance of quality characteristics of fresh-cut apple slices

A commercial and three experimental wash treatments for fresh-cut apple slices were evaluated for their ability to affect survival of foodborne pathogens and to maintain quality characteristics measured instrumentally and by sensory analysis. For each apple variety (Fuji and Granny Smith), instrumental firmness, cut surface color, and sensory scores for firmness and flavor of fresh-cut apple slices treated with the commercial and experimental wash solutions were similarly maintained during storage (6 days at 5°C). Prior to their use with apple slices, all three experimental wash solutions reduced the survival of Salmonella serovar Typhimurium and Vibrio cholera by 5 logs or more and the experimental solution at pH 2.0 also reduced survival of Escherichia coli O157:H7, Listeria monocytogenes and Shigella flexneri by at least 5 logs, whereas the commercial wash solution had antibacterial activity only against V. cholera. During treatment of apple slices, the wash solutions changed compositionally over time as indicated by a decrease in conductivity, increases in soluble solids content and osmolality, and changes in pH; and they lost their antibacterial activity. Keeping microbial safety in view, wash solutions should not be reused on multiple batches of sliced apples. Instead, alternative washing strategies that maintain the antimicrobial properties of the wash solutions need to be developed for fresh-cut apple slices.     

Comparative study on cloudy apple juice qualities from apple slices treated by high pressure carbon dioxide and mild heat

Qualities of cloudy apple juices from apple slices treated by high pressure carbon dioxide (HPCD) and mild heat (MH) were evaluated. Temperatures were from 25 to 65 °C, time 20 min, and pressure 20 MPa. Polyphenol oxidase (PPO) was completely inactivated by HPCD and its minimal residual activity (RA) by MH at 65 °C was 38.6%. RA of pectin methylesterase (PME) with HPCD was significantly lower than MH and its minimum was 18%. L value of cloudy apple juice from HPCD-treated apple slices was significantly greater than that from MH-treated apple slices, however, b value, browning degree (BD) and turbidity were lower. And no differences in a value, total soluble solids, pH and conductivity were observed. After 7-day storage at 4 °C, HPCD caused no BD alteration but a significant turbidity loss. MH increased BD at 55 and 65 °C, and led to turbidity loss from 35 to 65 °C. The turbidity was not well related to RA of PME.Industrial relevanceCloudy apple juice is one of the popular fruit juices, and it requires strict processing treatment conditions to protect its quality, especially to prevent enzymatic browning and cloud loss. HPCD is one promising novel non-thermal technique and is likely to replace or partially substitute thermal processes. This study analyzed the effect of HPCD as a pretreatment means on qualities of cloudy apple juice, including inactivating enzymes which are crucial to quality control. Available data provided in this study will benefit the fruit juice industry.     

Dual effectiveness of sodium chlorite for enzymatic browning inhibition and microbial inactivation on fresh-cut apples

The dual effectiveness of sodium chlorite for browning inhibition and microbial inactivation on fresh-cut apples was investigated and compared to other anti-browning and antimicrobial agents. Results indicate that sodium chlorite significantly (P < 0.001) inhibited the browning reaction of fresh-cut Red Delicious apples stored at 5 °C for 14 days. This treatment also significantly reduced polyphenol oxidase activities. Treatments with acidified sodium chlorite, calcium chloride, or calcium ascorbate exhibited strong inhibition on apple browning during the early storage, these treatment effects diminished after 7 days in storage. Combining calcium chloride with sodium chlorite further significantly (P < 0.001) improved the firmness of apple slices, and browning inhibition during storage. Additionally, treatments with acidified sodium chlorite, sodium chlorite, or the combination of sodium chlorite and calcium chloride significantly (P < 0.001) reduced Escherichia coli populations on fresh-cut apples by 3.0, 3.6, and 3.9 log cfu g⁻¹ over the water control. The dual effectiveness of sodium chlorite to inhibit enzymatic browning and inactivate E. coli may allow this compound to achieve a prominent role in improving the quality and safety of products in the fresh-cut apple and other food industries.