INFLUENCE OF 1-METHYLCYCLOPROPENE AND NATURESEAL ON THE QUALITY OF FRESH-CUT "EMPIRE" AND "CRISPIN" APPLES

Wounding during processing triggers physiological reactions that limits shelf life of fresh‐cut apples. Exposure of “Empire” and “Crispin” apples at harvest to the ethylene antagonist, 1‐methylcyclopropene (1‐MCP), on the maintenance of fresh‐cut quality was evaluated in combination with post‐cut dipping of NatureSeal^TM Efficacy of 1‐MCP on fresh‐cut physiology and quality depended on the storage duration and apple cultivar. Ethylene production of apple slices was inhibited by 1‐MCP but not by NatureSeal. Total volatiles produced by fresh‐cut apples were not affected by NatureSeal but by 1‐MCP when 1‐month stored “Crispin” apples were used. 1‐MCP influenced the quality attributes of fresh‐cut slices prepared from apples stored either 4 months in cold storage or 6 months in controlled atmosphere. Enzymatic browning and softening of the cut‐surface, TSS and total microbial growth were suppressed by 1‐MCP in “Empire” apples. The influence of 1‐MCP on quality attributes in “Crispin” apple slices was marginal.     

Effect of nano‐ZnO‐coated active packaging on quality of fresh‐cut ‘Fuji’ apple

A novel nanopackaging was synthesised by coating polyvinyl chloride (PVC) film with nano‐ZnO powder, and its effects on the preservation quality of fresh‐cut ‘Fuji’ apple were investigated at 4 °C for 12 days. Compared with the control (PVC film), nanopackaging significantly reduced the fruit decay rate (P < 0.05), as well as decreased the accumulation of malondialdehyde (MDA) from 74.9 nmol g^?1 in the control to 53.9 nmol g^?1 in the nanopackaging. Cutting caused an increase in ethylene level, suggesting wound‐induced ethylene production, which was suppressed in nanopackaging. Both the polyphenoloxidase and pyrogallol peroxidase activities were decreased in nanopackaging fruit. The initial appearance of apple slices was retained, and the browning index was prevented in nanopackaging samples, which was only 23.9, much lower than the control of 31.7 on day 12. These results indicated that nano‐ZnO active packaging could be a viable alternative to common technologies for improving the shelf‐life properties of ‘Fuji’ apples as a fresh‐cut product.     

Chitosan nanoparticle coatings reduce microbial growth on fresh‐cut apples while not affecting quality attributes

This study addressed the effects of chitosan‐based nanoparticles on microbiological quality, colour, polyphenol oxidase (PPO) and peroxidase (POD) and firmness of fresh‐cut ‘Gala’ apple slices during storage at 5 °C for 10 days. The treatments carried out were as follows: (i) slices pulverised with 110‐nm chitosan nanoparticles, (ii) slices pulverised with 300‐nm chitosan nanoparticles, (iii) 2 g L^?1 chitosan dissolved in 2% citric acid and (iv) noncoated samples. There was an increase in chroma and a proportional decrease in hue angle and lightness. Browning of the slices coated with conventional chitosan and control was slightly intense than those coated with chitosan nanoparticles of 110 and 300 nm. The PPO and PDO activities increased with time for all samples, with irrelevant difference among the treatments. Flesh firmness did not change for any treatment and period. Coatings with chitosan nanoparticles of 110 nm showed higher antimicrobial activity against moulds and yeasts, and mesophilic and psychrotrophic bacteria than the other treatments. No Salmonella, and total and faecal coliforms were detected. This investigation supports the potential use of chitosan nanoparticles as edible coatings in controlling microbial activity in fresh‐cut apples.     

The effectiveness of ozone and acidulant treatments in extending the refrigerated shelf life of fresh-cut potatoes

Abstract: The objective of the study was to determine the effectiveness of acidulant dip treatments (with or without aqueous ozone) to reduce enzymatic browning and to extend the shelf life of fresh‐cut potato slices during refrigerated storage (4 °C) for 28 d. Potato slices subjected to aqueous ozone (2 ppm) had significantly (P≤ 0.05) higher L‐values and lower a‐values, but ozone did not appear to have any effect on aerobic plate counts (APCs) or polyphenol oxidase (PPO) activity. NatureSeal (NS) and sodium acid sulfate (SAS) were the most effective acidulant treatments in reducing browning (significantly [P≤ 0.05] higher L‐values, lower a‐values, and browning index values) regardless of ozone treatment. NS and SAS also had lower PPO activity compared to other treatments on days 0 and 28, and significantly (P≤ 0.05) lower APCs (≤2.00 log CFU/g) over refrigerated storage. Therefore, the SAS treatment was comparable to NS, a commercially available product, and showed promise as an effective antibrowning dip to reduce browning and spoilage in fresh‐cut potato products. Practical Application: A 1% SAS dip treatment which included 1% citric and 1% ascorbic acid was found to be an effective antibrowning dip for fresh‐cut potatoes along with NatureSeal®'s PS‐10, compared to other treatments. They were both effective in maintaining low microbial counts over refrigerated storage. Additionally, aqueous ozone washes (2 ppm) showed significant benefits to reduce browning; however, ozone did not affect microbial counts or PPO enzyme activity. Therefore, the SAS treatment could have potential use in the fruit and vegetable industry to reduce browning and spoilage in fresh‐cut potato products.     

Antibrowning and Antimicrobial Properties of Sodium Acid Sulfate in Apple Slices

ABSTRACT: There are few available compounds that can both control browning and enhance microbial safety of fresh‐cut fruits. In the present study, the antibrowning ability of sodium acid sulfate (SAS) on “Granny Smith” apple slices was first investigated in terms of optimum concentration and treatment time. In a separate experiment, the apple slices were treated with water or 3% of SAS, calcium ascorbate, citric acid, or acidified calcium sulfate for 5 min. Total plate count, color, firmness, and tissue damage were assessed during a 21‐d storage at 4 °C. Results showed that the efficacy of SAS in inhibiting browning of apple slices increased with increasing concentration. A minimum 3% of SAS was needed to achieve 14 d of shelf life. Firmness was not significantly affected by SAS at 3% or lower concentrations. Antibrowning potential of SAS was similar for all treatment times ranging from 2 to 10 min. However, SAS caused some skin discoloration of apple slices. When cut surface of apple slices were stained with a fluorescein diacetate solution, tissue damage could be observed under a microscope even though visual damage was not evident. Among the antibrowning agents tested, SAS was the most effective in inhibiting browning and microbial growth for the first 14 d. Total plate count of samples treated with 3% SAS was significantly lower than those treated with calcium ascorbate, a commonly used antibrowning agent. Our results suggested that it is possible to use SAS to control browning while inhibiting the growth of microorganisms on the apple slices if the skin damage can be minimized. Practical Application: Fresh‐cut apples have emerged as one of the popular products in restaurants, schools, and food service establishments as more consumers demand fresh, convenient, and nutritious foods. Processing of fresh‐cut apples induces mechanical damage to the fruit and exposes apple tissue to air, resulting in the development of undesirable tissue browning. The fresh‐cut industry currently uses antibrowning agents to prevent discoloration. However, the antibrowning solutions can become contaminated with human pathogens such as Listeria monocytogenes, and washing of apple slices with the contaminated solutions can result in the transfer of pathogens to the product. It would be ideal if an antibrowning compound prevented the proliferation of human pathogens in solutions and minimized the growth of pathogens during storage. The study was conducted to investigate antibrowning and antimicrobial properties of sodium acid sulfate (SAS) in comparison with other common antibrowning agents on Granny Smith apples. Results showed that among the antimicrobial agents we tested, SAS was the most effective in inhibiting browning and microbial growth for 14 d at 4 °C. However, SAS caused some skin discoloration of apple slices. Overall, SAS can potentially be used to inhibit tissue browning while reducing the microbial growth on apple slices. The information is useful for the fresh‐cut produce industry to enhance microbial safety of fresh‐cut apples while minimizing browning, thus increasing the consumption of the health benefiting fresh fruit.     

Effect of 1‐methylcyclopropene on anthracnose rot caused by Colletotrichum acutatum and disease resistance in loquat fruit

BACKGOUND: Loquat (Eriobotrya japonica Lindl.) fruit are susceptible to fungal decay during postharvest storage at ambient temperature. The control of postharvest diseases of loquat is based primarily on the use of synthetic fungicides. To look for an alternative method for disease control, we investigated the effect of 1‐methylcyclopropene (1‐MCP) on controlling anthracnose rot caused by Colletotrichum acutatum of loquat fruit. RESULTS: 1‐MCP treatment significantly reduced decay incidence of loquat fruit. The treatment markedly inhibited accumulation of superoxide radicals and hydrogen peroxide and maintained higher superoxide dismutase, catalase and ascorbate peroxidase. Meanwhile, 1‐MCP treatment induced higher activities of two defense‐related enzymes—chitinase and β‐1,3‐glucanase—during 6 days' storage. Furthermore, the treatment inhibited increases in fruit firmness and internal browning index, and maintained higher extractable juice rate, total soluble solids and titratable acidity contents, thereby delaying the development of senescence. CONCLUSION: 1‐MCP was effective in reducing decay and might have enhanced the disease resistance in loquat fruit by increasing chitinase and β‐1,3‐glucanase, and maintained natural resistance by delaying senescence development. Copyright © 2010 Society of Chemical Industry     

1‐Methylcyclopropene affects the antioxidant system of apricots (Prunus armeniaca L. cv. Búlida) during storage at low temperature

BACKGROUND: Apricots (Prunus armeniaca cv. Búlida) were treated with 1 mL L^?1 1‐methylcyclopropene (1‐MCP) immediately after harvest and stored in air at 2 °C for 21 days. Antioxidant levels (ascorbic acid and carotenoids), enzymatic antioxidant activities (superoxide dismutase (SOD) and unspecific peroxidase (POX)) and total antioxidant capacity (trolox equivalent antioxidant capacity (TEAC)) were determined. The level of oxidative stress was also established by measuring ion leakage during storage. The changes in the antioxidant potential of apricots were related to the capacity of 1‐MCP to increase their commercial life. RESULTS: 1‐MCP‐treated fruits exhibited higher SOD activity, whereas POX activity was significantly higher only after 21 days at 2 °C. Treated fruits also exhibited better retention of ascorbate and carotenoids and higher TEAC during storage. In accordance with these observations, lower ion leakage values were detected in 1‐MCP‐treated apricots. CONCLUSION: Taken together, these results suggest that 1‐MCP conferred a greater resistance to oxidative stress. This, along with the reduction in ethylene production, could contribute to the increase in commercial life and nutritional value observed in 1‐MCP‐treated apricots. Copyright © 2010 Society of Chemical Industry     

Changes in browning‐related components of apple slices during different stages of instant controlled pressure drop‐assisted hot air drying (AD‐DIC)

The effect of instant controlled pressure drop‐assisted hot air drying (AD‐DIC) on browning‐related components in apple slices was studied. Results showed the AD temperature had no significant effect on colour index of final apple slices. The aspartic acid, glutamic acid, lysine, histidine, arginine, sucrose and dehydroascorbic acid (DHAA) in apple slices increased firstly during the AD process and then decreased during DIC process. The fructose, glucose, reduced ascorbic acid and major phenolic compounds reduced with the abrupt increase of 5‐hydroxymethylfurfural (5‐HMF) during AD‐DIC. There were significant correlations (P < 0.05) among moisture content (w.b.), water activity (a_w), water state, reduced ascorbic acid, DHAA, chlorogenic acid, procyanidin B₁, (+)‐catechin, (?)‐epicatechin and phlorizin during AD‐DIC. The colour difference showed that the major browning reaction of apple slices during the predrying process was enzymatic browning, while nonenzymatic browning played a crucial role on green‐red value (CIE a* value) during DIC.     

Slicing increases antioxidant capacity of fresh‐cut lotus root (Nelumbo nucifera G.) slices by accumulating total phenols

Slicing is an abiotic stress during fresh‐cut lotus root slices (FLS) preparation. To evaluate the potential ability of slicing to induce antioxidant capacity (AC) in FLS, fresh lotus roots were sliced into 0.4 cm thick slices and stored at 7 °C for 7 days using intact root segments as control. Results showed slicing induced 68.3% higher phenylalanine ammonia‐lyase (PAL) activity and parallel 130.5% more total phenol (TP) accumulation after 7 days storage compared to control. AC values in FLS assayed by FRAP and ABTS^●+ were 41.5% and 93.8% more than those in control samples at the end of storage, respectively. Such increases in AC values were mainly attributed to TP accumulation as a positive correlation existed between AC and TP. However, slicing significantly accelerated FLS browning by increasing the polyphenol oxidase (PPO) activity during storage. Nevertheless, FLS was still marketable with the maximum browning index of 1.9 after 7 days storage.     

Oxidative behaviour of fresh‐cut ‘Fuji’ apples treated with stabilising substances

BACKGROUND: Although changes in the quality of fresh‐cut products treated with chemical stabilisers have been extensively described in the literature, very little is known about the physiology of these products. This work aims to describe the physiological aspect and particularly the effects of chemical preservatives on the oxidative behaviour of fresh‐cut apples. RESULTS: Immediately after treatment, the samples treated with the anti‐browning agents (ascorbic acid + cysteine) exhibited a sharp increase in H₂O₂ levels (a five‐fold increase when compared to the other samples) and peroxidative damage, especially at the beginning of the storage period (two‐fold increase after 1 day). In line with this result, peroxidase (POX) activity decreased by 50% during the first day of storage, but no significant changes in superoxide dismutase (SOD) and catalase (CAT) activities were found between the different samples. H₂O₂ accumulation was not attributed to the action of cysteine but to a specific action of ascorbic acid, which mainly acted as a pro‐oxidant under these conditions. CONCLUSION: The results presented in this work showed that ascorbic acid cause important oxidative damage in fresh‐cut Fuji apples. Alternatives are required to prevent detrimental loss of quality resulting from this oxidative action. Copyright © 2008 Society of Chemical Industry     

Amino acid composition and anti‐polyphenol oxidase of peptide fractions from sericin hydrolysate

Sericin hydrolysate (SH), prepared from enzymatic hydrolysis of sericin, was investigated for its antipolyphenol oxidase (PPO) properties. SH decreased PPO activity from both purified mushroom PPO and extracts from apple and eggplant, and retarded browning in fresh‐cut apple and eggplant. SH was a competitive inhibitor using catechol as a substrate. SH exhibited copper ion‐chelating power and reducing power abilities. Fractionation of SH using size exclusion chromatography resulted in four fractions, designated as F1, F2, F3 and F4, with PPO inhibition of 35.75%, 3.89%, 24.52% and 14.75%, respectively. Ser and Asp were major amino acids found in F1. Amino acid sequences in F1, as investigated by LC‐MS/MS using de novo sequencing, contained a high ratio of amino acids with chelating ability. Moreover, amino acids with reducing power ability and with antityrosinase ability were also identified in the sequences.     

Browning inhibition on fresh‐cut chestnut kernel by exogenous nitric oxide

The potential usage of nitric oxide (NO) as a powerful anti‐browning agent in fresh‐cut chestnut kernels was investigated. Chestnut kernels were dipped in 0, 1, 5 or 10 μm NO solutions for 10 min, respectively, and then stored at 20 °C. Changes of browning index and colour were evaluated, while content of total phenols, activities of polyphenol oxidase (PPO) and peroxidase (POD) and individual phenolic compounds were measured. The results showed that NO treatment delayed browning and lightness of chestnut kernels and 5 μm NO treatment had the best control effect compared with others. PPO and POD activities were inhibited and total phenolic content was increased in NO‐treated fruit, and 5 μm NO significantly increased the content of catechin, chlorogenic acid, syringic acid, phloretic acid and ferulic acid but inhibited that of tannic acid. However, it had no significant effect on caffeic acid.     

热处理结合γ-氨基丁酸对鲜切苹果生理特性和品质的影响

为提高鲜切苹果贮藏期的品质,本文以富士苹果为材料,研究了45 ℃水整果浸泡(2 min)、果实鲜切后γ-氨基丁酸(GABA)处理(1.5%,10 min)及热处理结合GABA对贮藏期间苹果切片品质的影响。结果表明:4 ℃贮藏8 d时,对照组苹果切片感官品质下降迅速,可溶性固形物和可滴定酸含量降低,L*值降低,BI值升高,褐变明显发生,多酚氧化酶(PPO)和过氧化物酶(POD)活性升高,DPPH自由基清除率下降,贮藏后期MDA大量积累。与对照相比,热处理、GABA处理及热处理结合GABA均获得较高的感官评分,抑制了果肉可溶性固形物和可滴定酸含量的下降,保持较高的L*值,减轻褐变的发生,提高了总酚含量,抑制了多酚氧化酶(PPO)和过氧化物酶(POD)活性上升,减少了抗氧化物质的损失,保持较高的DPPH清除率,并减轻了MDA积累,其中,以热处理结合GABA效果最好。     

Suitability for minimal processing of non‐melting clingstone peaches

Clingstone non‐melting peach cultivars (Prunus persica L. Batsch) are used primarily for canning, but their processing as fresh‐cut products is also of interest. Four clingstone peach cultivars (‘Andross’, ‘Babygold 8′, ‘Calante’ and ‘Romea’) were evaluated for their suitability for minimal processing (washing, peeling and slicing) followed by storage for 9 days at 4 °C in a modified atmosphere using microperforated films. Romea cultivar, which has low polyphenol oxidase (PPO) enzymatic activity, proved to be the most suitable cultivar for minimal processing, given its lower degree of browning as well as the results from a sensory evaluation. Maturity indicators varied slightly during storage at a different degree depending on cultivars. We have found that PPO activity and browning potential are adequate indicators for surface browning in fresh‐cut non‐melting peaches.     

Effects of argon enriched low-oxygen atmospheres and of high-oxygen atmospheres on the kinetics of polyphenoloxidase (PPO)

Abstract: The reported benefits of enrichment of air atmospheres with argon or oxygen for control of enzymatic browning were investigated by determining the effects of these atmospheres on PPO kinetics. Kinetics of purified apple PPO and a commercially available mushroom PPO were studied in an in vitro model system. Enrichment with argon produced greater inhibitory effects than the current industry practice of enrichment with nitrogen. Km^app values (mM) for apple PPO in 3%O₂/97%Ar, 3%O₂/97%N₂, and air, were 133, 87, and 48, respectively. The data indicate that inhibition by both gases is competitive, and also support the hypothesis that the greater inhibitory effect of argon was proportional to the size of the Van der Waals radius of argon against nitrogen (1.91Å against 1.54Å). Much smaller inhibitory effects were observed in the presence of 80% O₂ (Km^app 57mM), and the nature of this inhibition was less clear. The results suggest that the benefits of argon enrichment may be relatively small, and may require critical enzyme, substrate, and gas levels to be successful. However, these benefits may be exploitable commercially in some fresh‐cut products, and may allow less anoxic atmospheres to be used. Practical Application: Control of enzymatic browning without sulfites continues to be a challenge in some fresh‐cut products. While sporadic benefits of these atmospheres in control of enzymatic browning have been reported, results have been inconsistent in commercial practice. The results suggest that the benefits of argon enrichment may be relatively small, and may require critical enzyme, substrate, and gas levels to be successful. However, these benefits may be exploitable commercially in some fresh‐cut products, and allow less anoxic atmospheres to be used.     

Oxidative behaviour of Blanquilla pears treated with 1‐methylcyclopropene during cold storage

The increasing use of 1‐methylcyclopropene (1‐MCP) to extend the commercial life of fruit constitutes an attractive way of improving packing house competitiveness. This compound prevents the effects of ethylene in a wide range of fruit and vegetables. However, despite the extensive literature relating to this action on ethylene, little is known about its other physiological effects. In this work, pears (Pyrus malus L cv Blanquilla) were treated with 100 ppb 1‐MCP immediately after harvest and stored in air for 5 months. Differences in oxidative stress and in antioxidant potential between controls and 1‐MCP‐treated fruits were established, determining the changes in the levels of hydrogen peroxide, ascorbate content and ionic leakage during storage. Activities of the H₂O₂‐generating enzyme superoxide dismutase (EC 1.15.11) and the H₂O₂‐scavenging enzymes catalase (EC 1.11.1.6), ascorbate peroxidase (EC 1.11.1.11) and unspecific peroxidase (EC 1.11.1.7) were also determined. 1‐MCP‐treated fruits exhibited lower levels of hydrogen peroxide, ascorbate and lower ionic leakage during storage. In accordance with this result, 1‐MCP‐treated fruits also exhibited higher enzymatic antioxidant potential. These results challenge the hypothesis that the beneficial effects of 1‐MCP on ripening were not exclusively due to its action on ethylene but also to an increase in antioxidant potential in pear. Copyright © 2004 Society of Chemical Industry     

曲酸、抗坏血酸及柠檬酸对鲜切苹果褐变的影响

以鲜切苹果为试材,分别用曲酸、抗坏血酸和柠檬酸浸泡3 min,于4℃存放9 d,对鲜切苹果的硬度、色泽、总酚、可溶性醌、多酚氧化酶活性、维生素C等指标进行分析。结果表明,3种有机酸对鲜切苹果的硬度和多酚氧化酶的影响差异不显著(P>0.05),而对褐变、总酚和维生素C影响差异显著(P<0.05)。综合来看,3种有机酸均对鲜切苹果褐变都有抑制效果,而曲酸明显优于柠檬酸和抗坏血酸,说明曲酸是一种潜在的鲜切苹果保鲜和护色剂。     

Effect of Natural Antibrowning Agents on Color and Related Enzymes in Fresh-Cut Fuji Apples as an Alternative to the Use of Ascorbic Acid

ABSTRACT:  Polyphenoloxidase (PPO) and peroxidase (POD) were evaluated in fresh-cut Fuji apple slices and the effect of the individual or combined use of ascorbic acid, 4-hexylresorcinol, N-acetylcysteine, and glutathione on their respective activities was determined. Additionally, color changes during storage at 4 °C were measured throughout 14 d of storage. PPO activity increased with storage time and was inhibited by the individual use of N-acetylcysteine and glutathione. POD activity in the apple slices was effectively inhibited by the combined use of ascorbic acid with any of the other antibrowning agents. On the other hand, an individual treatment with 1% N-acetylcysteine helped in maintaining the color of fresh-cut apples during 14 d of storage, whereas the use of ascorbic acid was not enough to prevent color deterioration of the apple slices from the 1st day of storage. The results obtained corroborated the effectiveness of other natural antibrowning agents over the traditional use of ascorbic acid in the control of the enzymatic browning in the fresh-cut fruit industry.     

Quality and antioxidant capacity of fresh‐cut apple wedges enriched with honey by vacuum impregnation

The effect of vacuum impregnation (VI) of fresh‐cut apple wedges with honey, in presence and absence of a browning inhibitor on physicochemical, sensory and antioxidant properties over 7 days of storage at 2–4 °C was studied. Infusion of wedges with honey resulted in very little weight change indicating loss of internal water and ingress of honey carbohydrates into the wedges, hence the correlation coefficients with soluble solids content (r = ?0.91) and dry matter (r = ?0.77). Water infused samples showed the highest water uptake resulting in an increase in weight of 30%. Browning (P < 0.001) and firmness (P < 0.001) of apple wedges were the quality parameters most affected by VI. Samples dipped in browning inhibitor prior AS1 showed slightly better performance than undipped wedges with regard to browning and firmness. Total phenol content and antioxidant activity were significantly (P < 0.001) lower for honey infused apple wedges.     

Impact of Mixtures of Different Fresh‐Cut Fruits on Respiration and Ethylene Production Rates

Packaging and storage of fresh‐cut fruits and vegetables are a challenging task, since fresh produce continue to respire and senesce after harvest and processing accelerates the physiological processes. The response on respiration and ethylene production rates of fresh produce to changes in O₂ and CO₂ concentrations and temperature has been extensively studied for whole fruits but literature is limited on processed and mixed fresh‐cut fruits. This study aimed to investigate the effects of mixing various proportions of fresh‐cut fruits (melon chunks, apple slices, and pineapples cubes) on respiration and ethylene production rates and to develop predictive models for modified atmosphere packaging. The experiment was designed according to a simplex lattice method and respiration and ethylene production rates were measured at 10 °C. Results showed that single component pineapple cubes, apple slices, and melon chunks, in this order, had significant constant coefficients (P = 0.05) and the greatest impact on respiration rate while the interactive binary and tertiary coefficients were insignificant. For ethylene production rates, single component apple slices, melon chunks, and pineapple cubes, and their 3‐component mixtures, in this order, had significant constant coefficients (P = 0.05) while binary coefficients were insignificant. Mathematical models were developed and validated; the cubical model was the best to describe the influence of proportion of fruit on respiration and ethylene production rates, however, considering simplicity the linear part of the model is recommended to quantify respiration and ethylene production rates of mixed fresh‐cut fruits.