Quality Improvement of Fresh-Cut Endive (<Emphasis Type="Italic">Cichorium endivia</Emphasis> L.) and Recycling of Washing Water by Low-Dose UV-C Irradiation

Superficial short-wavelength ultraviolet (UV-C) treatment (1.2 kJ/m²) of fresh-cut endive was combined with conventional cold (4 °C, 120 s) and innovative warm (45 °C, 120 s) water washing prior to and after irradiation in order to improve its microbial and sensory quality including physiological properties. UV-C doses applied exerted only minor physiological stress on the plant tissue, irrespective of the washing procedure as indicated by largely unaltered headspace gas compositions, chlorophyll fluorescence maximum quantum yields (F _v/F _m), and retention of chlorophylls and β-carotene. Independent of the washing procedure applied, phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD) activities were slightly inhibited by UV-C irradiation. As a result of UV-C irradiation, significantly improved microbiological and sensory quality was retained during the entire storage period, particularly, when applied after washing. Being applicable in organic fresh-cut production, UV-C represents a valuable alternative to chlorine application to washing water. The most efficient decontamination (2.1 log₁₀ units) of fresh-cut endive was achieved by combining warm water washing with subsequent UV-C irradiation. Furthermore, when UV-C lamps were integrated into the water tank of a continuous industrial washing machine, the microbial loads of the process water were also significantly lowered. Accordingly, in-line UV-C decontamination of process water may be instrumental in minimizing both fresh water consumption and the risk of cross-contamination.     

Chlorophyll Fluorescence Imaging for Monitoring the Effects of Minimal Processing and Warm Water Treatments on Physiological Properties and Quality Attributes of Fresh-Cut Salads

In this study, chlorophyll fluorescence imaging (CFI) was used to monitor plant stress induced by cutting of mini romaine lettuce (Lactuca sativa L. var. longifolia) and by cutting and washing of endive (Cichorium endivia L.) during storage. Regarding the more detailed study of endive fresh-cut salads, we additionally monitored respiratory activity, phenylalanine ammonia lyase (PAL) activity, contents of plant pigments, and cut edge browning. Determination of maximum quantum efficiency F _v/F _m was feasible through sealed consumer-sized film bags, thus, enabling the non-invasive monitoring of both fresh-cut salad types in the corresponding modified atmosphere during storage. Cutting of romaine lettuce provoked a partially reversible drop of F _v/F _m during the first 24 h. Subsequently, F _v/F _m of cut romaine strongly decreased with elapsing shelf life, whereas intact leaves exhibited only a slight decline. Regarding minimally processed endive, warm water washing progressively reduced F _v/F _m with increasing heat exposure, while respiratory activities and the content of accessory pigments remained unaffected. The heat-dependent decrease of F _v/F _m was correlated to the inhibition of the PAL activity. Mildly warm washing (40 °C, 120 s; 45 °C, 60 s) reduced PAL activities, while F_v/F_m remained widely unaffected and visual quality was only partially improved. However, warm water washing at elevated temperatures (45 °C, 120 s; 50 °C, 30–60 s) enabled maximum visual quality retention, accompanied by a significant decrease of F _v/F _m. CFI may represent a useful tool to monitor the stress conditions due to cutting and warm water treatments, hence, allowing the systematic improvement of fresh-cut produce.     

Effect of temperature and chlorination of pre-washing water on shelf-life and physiological properties of ready-to-use iceberg lettuce

The effects of cold and warm, chlorinated water as well as warm water without chlorination for pre-washing trimmed, cored iceberg lettuce heads was assessed regarding the shelf-life and physiological properties of the resulting ready-to-use (RTU) produce. On a pilot-plant scale, lettuce heads were shredded with or without pre-washing (50 °C, no chlorine; 4 and 50 °C, 200 mg/l free chlorine; 60 s). After shredding, lettuce was washed for 90 s (tap water, 4 °C), spin-dried, packaged in 200 g consumer-sized bags, and stored at 4 °C for ≤ 9 days. Samples were analyzed for their headspace O₂ and CO₂ levels, sensory properties, microbiological status, and phenylalanine ammonia-lyase (PAL) activity at regular intervals throughout processing and storage. Parallelly, instrumental color and texture measurements were performed. All pre-washing procedures of lettuce heads lowered the initial counts of total aerobic bacteria, pseudomonades, and Enterobacteriaceae by ≥ 1.63, ≥ 1.55, and ≥ 1.85 log₁₀ cfu/g, respectively, while the single-wash of shredded lettuce in tap water without any pre-washing resulted in significantly smaller reduction rates (0.23, 0.11, and 0.71 log₁₀ cfu/g, respectively). During storage, all pre-washing procedures had a persistent effect on bacterial counts of the RTU lettuce. Furthermore, all pre-washing procedures delayed vascular tissue browning at cut edges and retarded the decline in the overall visual quality of the samples. Whereas wound-induced PAL synthesis was reduced by the use of warm water (± chlorine), O₂ depletion and CO₂ evolution in the corresponding bags were slightly enhanced, thus proving that processing kept the food as a living tissue.Industrial relevanceReady to use fresh like produce is getting increasing attention and industrial relevance. The aim of this study was to specifically overcome problems associated with product heterogeneity. Interestingly, the use of warm tap water without chlorination as a pre-washing step proved as effective alternative to the application of cold chlorinated water without substantially compromising vitality and freshness of the product.     

Sanitizer treatments alleviate lignification of sliced few-flower wildrice (Zizania latifolia Turcz.)

To investigate the effects of sanitation processing on the lignification of few-flower wildrice (FFW), fresh-cut FFW was treated with water (control), 80 mg/L peroxyacetic acid (PAA), 100 mg/L ClO₂ or 50 mg/L H₂O₂, packed in polyethylene film bags and stored at 2 °C for 21 days. Firmness, lignin, cellulose, hemicellulose and lignin forming related enzymes activities were examined. Sanitizer treatments inhibited the increases of firmness, lignin and cellulose than the control. The changes of hemicelluloses did not show a difference between the control and PAA treatment. An increase in the activities of phenylalanine ammonia lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO), and a reduction in catalase (CAT) and superoxide dismutase (SOD) activities, were detected in the sliced FFW in the incompatible interaction. Compared with the control, sanitizers suppressed the activities of PAL, POD and PPO, but enhanced the activities of SOD and CAT during 21 days of storage. These enzymatic activities varied with different sanitizers. These results show that 80 mg/L peroxyacetic acid (PAA), 100 mg/L ClO₂ or 50 mg/L H₂O₂ sanitation processing can maintain tenderness, alleviate the lignification and fibrosis of fresh-cut FFW.     

Changes in appearance and natural microflora on iceberg lettuce treated in warm,chlorinated water and then stored at refrigeration temperature

The objective of this study was to determine the effect of warm, chlorinated water on the survival and subsequent growth of naturally occurring microorganisms and visual quality of fresh-cut iceberg lettuce. After dipping cut lettuce leaves in water containing 20 mg l⁻¹free chlorine for 90 s at 50°C, samples were stored at 5 or 15°C for up to 18 or 7 days, respectively. Populations of aerobic mesophiles, psychrotrophs, Enterobacteriaceae, lactic acid bacteria, and yeasts and molds were determined. The visual appearance and development of brown discoloration were monitored. Treatment of lettuce in warm (50°C) chlorinated water delayed browning of lettuce. Shelf life of lettuce stored at 5°C, as determined by subjective evaluation of color and general appearance, was about 5 days longer than that of lettuce stored at 15°C. Treatment in warm (50°) water, with or without 20 mg l⁻¹chlorine, and in chlorinated water at 20°C significantly (α= 0·05) reduced the initial population of mesophilic aerobic microflora by 1·73–1·96 log₁₀cfu g⁻¹. Populations increased, regardless of treatment, as storage time at 5°C and 15°C increased. The same trends were observed in populations of psychrotrophs and Enterobacteriaceae. Yeast populations increased slightly in lettuce stored at 5°C but were consistently about 3 logs lower than mesophilic aerobes. Populations of molds and lactic acid bacteria were less than 2 log₁₀cfu g⁻¹throughout storage at 5 or 15°C. Results suggest that heat (50°C) treatment may have delayed browning and reduced initial populations of some groups of micro-organisms naturally occurring on iceberg lettuce, but enhanced microbial growth during subsequent storage.     

二氧化碳气调包装对鲜切结球莴苣贮藏品质和生理的影响

研究4℃、10% O2结合不同体积分数CO2(10%～50% CO2)处理对鲜切结球莴苣的主要品质和生理指标变化的影响。结果表明：高体积分数CO2导致了细胞膜通透性增加;10% O2＋30% CO2气体组合显著抑制了多酚氧化酶、过氧化物酶和过氧化氢酶的活性,延缓了组织的衰老和褐变,并较好地保持了鲜切结球莴苣中叶绿素、VC和还原糖含量。感官评价结果表明,在10% O2＋30% CO2气体组合条件下,鲜切结球莴苣贮藏15d仍具有商品价值。     

Effect of Water Jet Cutting and Moderate Heat Treatment on Quality of Fresh-Cut Red Oak Leaf Lettuce (Lactuca sativa L. var. crispa)

Fresh-cut red oak leaf lettuce was produced by six different processing lines in order to assess the effect of water jet cutting (nozzle diameter 0.1 mm, pressure 2,500 bar) versus blade cutting as well as washing with cold and warm water (4 and 45 °C, 120 s) prior to and after shredding, respectively. Throughout refrigerated storage (4 °C, 12 days), O₂ and CO₂ levels in the modified atmosphere of the consumer-sized sample bags were monitored, and fresh-cut products and process water were subjected to microbiological analysis. As further quality parameters, phenylalanine ammonia lyase (PAL) activity as well as levels of chlorophyll a and b, β-carotene and cyanidin 3-O-(6”-O-malonyl)-glucoside were determined by HPLC with diode array detection (HPLC-DAD) and HPLC coupled with diode array detection and tandem mass spectrometry (HPLC-DAD-MSⁿ) throughout storage. Additionally, visual appearance and cut edge browning were assessed by sensorial evaluation and stereo microscopy on storage day 8. Microbiological quality throughout commercial shelf life was best retained by warm water washing of shredded lettuce. Furthermore, moderate heat treatment significantly reduced PAL activity and cut edge browning without affecting pigment contents and vitality of the lettuce tissue. Additionally, warm water treatment significantly lowered the microbial load in the process water. Throughout storage, water jet cutting did not affect the microbial, physiological and sensorial fresh-cut lettuce quality compared to blade cutting using a newly sharpened blade, thus indicating a similar degree of wounding due to the cutting techniques applied. The application of a pre-washing step prior to shredding was found to be suitable to reduce the risk of cross-contamination in subsequent process steps.     

Nitric oxide prevents wound-induced browning and delays senescence through inhibition of hydrogen peroxide accumulation in fresh-cut lettuce

As a source of bioactive ingredients, lettuce is a preferable component of a healthy diet. In recent years the production of fresh-cut produce has become a fast growing business. However, the shreds are highly sensitive to wound-induced browning and premature senescence that substantially reduces the visual and sensory qualities and shortens the shelf life. To improve the fresh-cut quality, in this work, short pre-storage exposure of shreds from butterhead and iceberg lettuce to nitric oxide (NO) gas was applied. It was found that fumigation with 100 and 200 ppm NO for 1 or 2 h remarkably inhibited the browning of the cut surface and of other injured leaf areas; NO treatment delayed the senescence and substantially prolonged the shelf life upon storage at 4 °C and 12 °C. To obtain information on the physiological processes involved in the wound response, the generation of hydrogen peroxide (H₂O₂) and the occurrence of cell death were analyzed. The results revealed that the wounding stimulated the accumulation of H₂O₂ thus generating oxidative stress leading to cell death. A correlation between elevated H₂O₂ levels, cut surface browning, senescence and storability of the fresh-cuts was established. In comparison to mature leaves, younger leaves expressed a lesser susceptibility to wound-induced browning and the associated oxidative stress. Applied NO strongly inhibited the H₂O₂ accumulation which may explain its beneficial effects.Industrial relevanceWe demonstrate that short treatments with NO gas substantially inhibit wound-induced browning and largely improve the storability of fresh-cut lettuce. This offers an option for adopting NO treatments for optimization of the post-processing conditions. Implementation of reported findings into practice will offer innovative technological solutions for improvement of the post-harvest quality of fresh-cut lettuce applicable for the industry, distributors and retailers. Moreover, our findings indicate that the browning disorder is to a large extent dependent on the severity of the wound-induced oxidative stress and cell death occurrence. This discovery opens a possibility for the development of metabolic and morphological markers appropriate for the prediction of the quality and shelf life of fresh-cut lettuce with perspective for expanding the research and introducing the tests toward other perishable leafy vegetables.     

Exogenous salicylic acid inhibits browning of fresh-cut Chinese water chestnut

The potential usage of salicylic acid (SA) as a powerful anti-browning agent in fresh-cut Chinese water chestnut (CWC) was investigated. The fresh-cut CWC were dipped for 1 min in solutions of 0, 1, 2 or 4 mM SA, then placed in trays over-wrapped with plastic films, and finally stored at 4 °C. Changes in color, eating quality, and disease incidence were evaluated, while activities of phenol-associated enzymes, polyphenol oxidase (PPO), peroxidase (POD) and phenylalanine ammonia lyase (PAL), and concentrations of total soluble solid, titratable acidity and ascorbic acid were measured. SA treatment delayed discoloration, maintained eating quality with higher content of the quality attributers, and reduced activities of or delayed the increases in activities of PPO, POD and PAL in fresh-cut CWC. However, SA had no significant inhibition of the activities of PPO and POD in an in vitro test, indicating that the beneficial effect of SA was indirect. Further research is needed to elucidate the inhibition of the surface browning of the fresh-cut CWC by SA.     

高浓度二氧化碳气调包装通过调节酚代谢抑制鲜切莲藕的酶促褐变

鲜切莲藕褐变的主要原因是酶促褐变,高浓度CO_2气调包装(Modified-atmosphere packaging,MAP)可以有效延缓鲜切果蔬褐变,而苯丙氨酸解氨酶(L-phenylalanine ammonia-lyase,PAL)、多酚氧化酶(Polyphenol oxidase,PPO)和过氧化物酶(Peroxidase,POD)的编码基因是引起果蔬褐变的主要基因。然而,高浓度CO_2 MAP对鲜切莲藕片PAL、PPO、POD酶及其编码基因表达的影响却鲜有报道。本文分析了100%CO_2MAP对鲜切莲藕贮藏过程中褐变度、总酚含量、PAL、PPO和POD酶活性及其编码基因表达的影响。结果表明:100%CO_2 MAP对延缓鲜切莲藕褐变有较好效果,且100%CO_2 MAP贮藏期间鲜切莲藕PAL、PPO和POD酶活性随褐变程度的增加而同步变化。此外,Nn PAL1,Nn PPOA和Nn POD2/3的表达变化与PAL,PPO和POD酶活性的变化及褐变相一致,说明高浓度CO_2 MAP可能通过下调Nn PAL1,Nn PPOA和Nn POD2/3的表达来延缓鲜切莲藕褐变。     

Influence of ultrasound treatment in combination with modified atmosphere on microorganisms and quality attributes of fresh-cut lettuce

The influence of ultrasound (US) treatment in combination with modified atmosphere packaging on microbial loads and quality attributes of fresh-cut lettuce was investigated during storage at 4 °C for up to 15 days. Fresh-cut lettuces were sonicated for different durations (0, 5, 10 and 15 min) by US (20 kHz, 226 W cm⁻²) and then packed in active modified atmosphere packaging (MAP). Results showed that US treatment combined with modified atmosphere effectively inhibited growth of bacteria, mold and yeast during storage. The US treatment for 10 min combined with MAP reduces mass losses and colour change, inhibits POD and PPO activities, conserves ascorbic acid and chlorophyll contents and maintains water distribution in fresh-cut lettuce. These results illustrated that US treatment combined with modified atmosphere was an effective preservation method to improve storage quality of fresh-cut lettuce.     

Thermal inactivation kinetics parameters of browning enzymes in starfruit (Averrhoa carambola L.) juice

This study aimed to evaluate the thermal inactivation kinetics of polyphenol oxidase (PPO) and peroxidase (POD) in starfruit juice. It followed the Malaysia Food Regulations 1985 and CODEX STAN 247-2005. Glucose, fructose and sucrose were the main sugars in starfruit juice. The total soluble solids, pH, titratable acidity, and total phenolics content of the starfruit juice produced were 8.13 ± 0.25 °Brix, 3.80 ± 0.05, 0.43% ± 0.02% malic acid, and 93.67 ± 4.96 mg GAEL⁻¹, respectively. Thermal inactivation kinetics of PPO and POD followed the first-order kinetic model. The decimal reduction time at 83.6 °C (D_83.6) of PPO and POD was 198.48 and 98.4 s, respectively, while the thermal resistance constant (z value) of PPO and POD was 12.8 and 5.4 °C, respectively. In conclusion, PPO might be a suitable signal for thermal processing on starfruit juice since it has higher heat resistance than POD.     

Efficacy of neutral electrolyzed water (NEW) for reducing microbial contamination on minimally-processed vegetables

Consumption of minimally-processed, or fresh-cut, fruit and vegetables has rapidly increased in recent years, but there have also been several reported outbreaks associated with the consumption of these products. Sodium hypochlorite is currently the most widespread disinfectant used by fresh-cut industries. Neutral electrolyzed water (NEW) is a novel disinfection system that could represent an alternative to sodium hypochlorite. The aim of the study was to determine whether NEW could replace sodium hypochlorite in the fresh-cut produce industry. The effects of NEW, applied in different concentrations, at different treatment temperatures and for different times, in the reduction of the foodborne pathogens Salmonella, Listeria monocytogenes and Escherichia coli O157:H7 and against the spoilage bacterium Erwinia carotovora were tested in lettuce. Lettuce was artificially inoculated by dipping it in a suspension of the studied pathogens at 10(8), 10(7) or 10(5) cfu ml(-1), depending on the assay. The NEW treatment was always compared with washing with deionized water and with a standard hypochlorite treatment. The effect of inoculum size was also studied. Finally, the effect of NEW on the indigenous microbiota of different packaged fresh-cut products was also determined. The bactericidal activity of diluted NEW (containing approximately 50 ppm of free chlorine, pH 8.60) against E. coli O157:H7, Salmonella, L. innocua and E. carotovora on lettuce was similar to that of chlorinated water (120 ppm of free chlorine) with reductions of 1-2 log units. There were generally no significant differences when treating lettuce with NEW for 1 and 3 min. Neither inoculation dose (10(7) or 10(5) cfu ml(-1)) influenced the bacterial reduction achieved. Treating fresh-cut lettuce, carrot, endive, corn salad and 'Four seasons' salad with NEW 1:5 (containing about 50 ppm of free chlorine) was equally effective as applying chlorinated water at 120 ppm. Microbial reduction depended on the vegetable tested: NEW and sodium hypochlorite treatments were more effective on carrot and endive than on iceberg lettuce, 'Four seasons' salad and corn salad. The reductions of indigenous microbiota were smaller than those obtained with the artificially inoculated bacteria tested (0.5-1.2 log reduction). NEW seems to be a promising disinfection method as it would allow to reduce the amount of free chlorine used for the disinfection of fresh-cut produce by the food industry, as the same microbial reduction as sodium hypochlorite is obtained. This would constitute a safer, 'in situ', and easier to handle way of ensuring food safety.     

真空浸渍辅助L-半胱氨酸处理对贮藏期鲜切马铃薯的护色作用

为研究L-半胱氨酸(L-cysteine,L-cys)对鲜切马铃薯的抗褐变机制,以鲜切马铃薯为研究对象,采用真空浸渍技术辅助0.7 g/L的L-cys溶液处理鲜切马铃薯,分析贮藏期鲜切马铃薯褐变指数(browning index,BI)、多酚氧化酶活性(polyphenol oxidase,PPO)、过氧化物酶活性(peroxidase,POD)、苯丙氨酸解氨酶活性(phenylalanineammonialyase,PAL)、总酚含量及抗氧化活性的变化。结果表明,在贮藏期,试验组鲜切马铃薯BI值、PPO活性、POD活性、PAL活性均显著低于对照组(p<0.05)。试验组总酚含量在贮藏0~6 d,显著低于对照组(p<0.05),但贮藏后期则显著上升(p<0.05)。另外,两组鲜切马铃薯抗氧化活性在贮藏期,均呈先上升后下降趋势。因此,结果表明,L-cys处理可以抑制鲜切马铃薯酶活性,从而延缓鲜切马铃薯在贮藏期间的褐变。     

Gamma irradiation inhibits browning in ready-to-cook (RTC) ash gourd (Benincasa hispida) during storage

Inhibition of browning in gamma irradiated (2 kGy) RTC ash gourd during storage (10 °C, 12 days) was investigated. Irradiation resulted in a significant increase in the content of α-resorcylic acid that was correlated with decreased PPO activity. Nature of the PPO inhibition was found to be of mixed and reversible type with K_i, 0.09 mM; K_is, 27.33 mM and IC₅₀ of 25 mM. During storage, the non-irradiated control samples exhibited increased oxidation of leached phenolic compounds at the surface as a consequence of changes in tissue micro-structure compared to the irradiated samples. Unlike control samples that exhibited enhanced PAL activity, quinone formation and browning, no increase in PAL activity and browning was noted in the irradiated samples during storage. Browning inhibition in stored radiation-processed (2 kGy) RTC ash gourd was thus proposed to be a synergistic effect of decreased quinone formation and reduced enzyme (PPO and PAL) activities.Industrial relevanceThe present study demonstrates the feasibility of gamma irradiation for browning inhibition in ready-to-cook (RTC) ash gourd during storage. Use of gamma irradiation for optimizing the post-processing conditions for improved visual appeal and storability of the fresh-cut produce in food industry is thus recommended. The possible use of alpha resorcylic acid as a natural browning inhibitor in fruits and vegetables is also of industrial relevance. The various approaches proposed in the study can be utilized by the food industry for maintaining visual quality of fresh-cut produce during storage thereby improving marketability of such produce.     

Effectiveness of organic acid,ozonated water and chlorine dippings on microbial reduction and storage quality of fresh‐cut iceberg lettuce

BACKGROUND: The comparative effects of organic (citric and lactic) acids, ozone and chlorine on the microbiological population and quality parameters of fresh-cut lettuce during storage were evaluated. RESULTS: Dipping of lettuce in 100 mg L⁻¹ chlorine solution reduced the numbers of mesophilic and psychrotrophic bacteria and Enterobacteriaceae by 1.7, 2.0 and 1.6 log₁₀ colony-forming units (CFU) g⁻¹ respectively. Treatment of lettuce with citric (5 g L⁻¹) and lactic (5 mL L⁻¹) acid solutions and ozonated water (4 mg L⁻¹) reduced the populations of mesophilic and psychrotrophic bacteria by 1.7 and 1.5 log₁₀ CFU g⁻¹ respectively. Organic acid dippings resulted in lower mesophilic and psychrotrophic counts than ozonated water and chlorine dippings during 12 days of storage. Lactic acid dipping effectively reduced (by 2.2 log₁₀ CFU g⁻¹) and maintained low populations of Enterobacteriaceae on lettuce for the first 6 days of storage. No significant (P > 0.05) changes were observed in the texture and moisture content of lettuce samples dipped in chlorine, organic acids and ozonated water during storage. Colour, β-carotene and vitamin C values of fresh-cut iceberg lettuce did not change significantly (P > 0.05) until day 8. CONCLUSION: Lactic and citric acid and ozonated water dippings could be alternative treatments to chlorine dipping to prolong the shelf life of fresh-cut iceberg lettuce. Copyright © 2007 Society of Chemical Industry     

鲜切雷竹笋冷藏过程中木质化机理的研究

研究鲜切雷竹笋在4℃冷藏条件下苯丙氨酸解氨酶(PAL)、过氧化物酶(POD)和多酚氧化酶(PPO)活力及丙二醛(MDA)、多酚、木质素含量的变化规律,探讨其木质化机理。结果显示：在冷藏过程中,PAL、POD活力、MDA含量呈先上升,后下降的趋势;PPO活力在前6d缓慢上升,第15天开始下降;多酚含量在冷藏前6d急剧下降,后缓慢上升,第12天又开始下降;木质素含量不断增加,基部为5%～26%,中部为3%～24%,尖部为2%～22%。结果表明：在冷藏期内,PAL、POD活力大幅度增加,是导致鲜切雷竹笋木质化的关键酶;酚类物质作为木质素合成的前体物质,参与木质素的合成;MDA可能参与鲜切雷竹笋的木质化进程,但需进一步验证;木质素含量从基部向尖部逐渐降低,木质化进程是从基部向尖部推进的。     

Effects of heat treatment on the quality of fresh-cut Chinese water chestnut

A heat treatment to inhibit browning and maintain the quality of fresh‐cut Chinese water chestnut was developed. Slices of Chinese water chestnut, cv. Guilin, were immersed in boiling water for 30 s, placed into film‐wrapped trays and then stored at 4 °C for up to 12 days. Changes in browning, eating quality and disease incidence were measured. The effect of heat treatment on the content of total phenolics and activities of phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD) was also evaluated. The heat treatment effectively prevented browning associated with PAL, PPO and POD activities and total phenolic content and delayed the decrease in eating quality, which is associated with reduced total soluble solids, titratable acidity and ascorbic acid, compared with fresh‐cut Chinese water chestnut. Inhibition of browning by heat treatment without microbial growth was achieved for 12 days of storage at 4 °C. These results showed that heat treatment effectively maintained the quality of fresh‐cut Chinese water chestnut.