壳聚糖涂膜对鲜切苹果贮藏品质的影响

为研究壳聚糖涂膜对鲜切苹果贮藏品质的影响,将鲜切寒富苹果分别用质量分数0.5%、1.0%、1.5%的壳聚糖浸泡3 min后沥干,用0.11 mm厚度的PE保鲜膜包装后置于4 ℃冷库中贮藏,每2 d测定与成熟衰老相关的生理生化指标。结果表明,适当质量分数的壳聚糖涂膜可保持苹果切块的感官品质、延缓营养物质下降、抑制微生物的繁殖,对鲜切苹果有较好的护色效果;壳聚糖涂膜也能较好地抑制多酚氧化酶活性,提高过氧化物酶活性。在研究的3 种质量分数中,1.0%壳聚糖处理对鲜切苹果的保鲜效果最好,能在4 ℃冷库12 d贮藏期中维持鲜切苹果的较好品质。     

Controlled release of thymol from zein based film

Active packaging materials, able to release antimicrobial compounds into foodstuffs, can be used in order to inhibit or slow down bacterial growth during storage. Zein-based mono and multilayer films were loaded with spelt bran and thymol (35% w/w) to obtain edible composite polymeric materials. Various composite systems were developed to control the release of thymol. In particular, the thickness of the layers and the biodegradable fibres amount were varied. Results highlight that thymol release rate decreased with the increase of the film thickness for both mono and multilayer films, without spelt bran addition. Conversely, a significant increase of thymol release rate with the increase of the bran concentration is recorded for both mono and multilayer films.Industrial relevanceIn recent years, food safety is an important area of concern to the food industry. This fact requires packaging to be an integral part of the preservation concept. Consequently additional antimicrobial activity from the packaging material can aid in shelf life extension. The present work is focused on the development of controlled release systems based on zein incorporated with an active compound, thymol and natural fibres. Release rate of thymol from the developed mono and multilayer films, as affected by layers thickness and fibres amount, was evaluated.     

Nanofibre-based bilayer biopolymer films: enhancement of antioxidant activity and potential for food packaging application

This study aimed to enhance the antioxidant property of biopolymer film without the incorporation of external agents. The active bilayer film with improved antioxidant activity has been developed by electrospinning zein, a prolamine of corn as nanofibre (average diameter of 286 nm) on solvent cast chitosan film. Zein nanofibres exhibited a slight increase in antioxidant activity as compared to solvent cast zein film. But, zein nanofibre coating on chitosan films significantly improved its antioxidant activity from 12.41% to 44.17%. The developed bilayer films were evaluated for its ability to prevent browning in minimally processed apple slices and compared with those of chitosan and zein films plasticised with polyethylene glycol. Higher surface to volume ratio and better affinity of zein nanofibres in the bilayer film helped enhance its anti-browning ability. Thus, zein nanofibre-coated chitosan bilayer films can be used as an effective anti-browning packaging material for the packing of minimally processed fruits.     

Quality of Fresh-cut Apple Slices as Affected by Low-dose Ionizing Radiation and Calcium Ascorbate Treatment

ABSTRACT: Although ionizing radiation effectively inactivates food-borne bacterial pathogens in fresh-cut fruits and vegetables, it may adversely affect product quality. In this study, the effects of calcium ascorbate (CaA) and ionizing radiation on quality of 'Gala' apple slices under modified atmosphere packaging were investigated. 'Gala' apple slices, treated with water or 7% CaA followed by either nonirradiation (0 kGy) or irradiation at 0.5 and 1.0 kGy, were stored at 10°C for up to 3 wk. The titratable acidity, pH, firmness, ascorbic acid content, color, and microflora population were measured weekly throughout storage. Irradiation did not affect titratable acidity and pH of sliced apples. Fruit slices softened during irradiation and storage, but this decrease in firmness during storage was reduced by the CaA treatment. Although the ascorbic acid content of apple slices treated with CaA decreased rapidly during storage, the ascorbic acid content was always higher in those treated samples than in the apple slices treated with water. Irradiation decreased both L * and hue values of apple slices. Hue values decreased during the entire storage period while L * increased during the 1st wk of storage, then decreased between 1 to 3 wk of storage. CaA increased L * and hue values of apple slices, suggesting CaA reduced browning, even in irradiated samples. The microflora population of apples slices was not affected by CaA, and CaA treatment did not alter the reduction in microflora by irradiation. The combination of CaA and irradiation enhanced microbial food safety while maintaining quality of fresh-cut apple slices.     

Antioxidant properties of apple slices stored in starch-based films

The aim of this study was to evaluate the antioxidant properties of apple slices stored in edible starch films enriched with white and green tea extracts. All results were compared to that obtained for apple slices stored in polyethylene films. The use of starch films, as carrier of antioxidants, prolonged the storage life and improved quality of fresh-cut apples at the end of storage; however, deteriorated their lightness and increased their browning. Apple slices coated in starch films enriched with tea extracts exhibited higher antioxidant properties than those without these additives, as well as those in polyethylene films.     

壳聚糖涂膜对鲜切苹果品质的影响

以山东红富士苹果为原材料,研究了不同浓度复合的壳聚糖、抗坏血酸及柠檬酸对鲜切苹果的外观和内部品质的影响。采用L9(34)正交实验设计,测定了贮藏过程中各组鲜切苹果的腐烂率、色泽、pH、可滴定酸、还原性糖等指标的变化情况。根据模糊权重法对贮藏4d的鲜切苹果外观和内部品质进行了综合评定。结果表明:选用2.0%柠檬酸、1.0%壳聚糖配制涂膜液和0.5%抗坏血酸溶液作为护色液,对鲜切苹果具有良好的保鲜效果。     

Examination of bacteriophage as a biocontrol method for salmonella on fresh-cut fruit: a model study

The preparation and distribution of fresh-cut produce is a rapidly developing industry that provides the consumer with convenient and nutritious food. However, fresh-cut fruits and vegetables may represent an increased food safety concern because of the absence or damage of peel and rind, which normally help reduce colonization of uncut produce with pathogenic bacteria. In this study, we found that Salmonella Enteritidis populations can (i) survive on fresh-cut melons and apples stored at 5 degrees C, (ii) increase up to 2 log units on fresh-cut fruits stored at 10 degrees C, and (iii) increase up to 5 log units at 20 degrees C during a storage period of 168 h. In addition, we examined the effect of lytic, Salmonella-specific phages on reducing Salmonella numbers in experimentally contaminated fresh-cut melons and apples stored at various temperatures. We found that the phage mixture reduced Salmonella populations by approximately 3.5 logs on honeydew melon slices stored at 5 and 10 degrees C and by approximately 2.5 logs on slices stored at 20 degrees C, which is greater than the maximal amount achieved using chemical sanitizers. However, the phages did not significantly reduce Salmonella populations on the apple slices at any of the three temperatures. The titer of the phage preparation remained relatively stable on melon slices, whereas on apple slices the titer decreased to nondetectable levels in 48 h at all temperatures tested. Inactivation of phages, possibly by the acidic pH of apple slices (pH 4.2 versus pH 5.8 for melon slices), may have contributed to their inability to reduce Salmonella contamination in the apple slices. Higher phage concentrations and/or the use of low-pH-tolerant phage mutants may be required to increase the efficacy of the phage treatment in reducing Salmonella contamination of fresh-cut produce with a low pH.     

Apple Wraps: A Novel Method to Improve the Quality and Extend the Shelf Life of Fresh-cut Apples

A novel method was developed to extend the shelf life and improve the quality of fresh-cut produce. Edible coatings and films were made from apple puree with various concentrations of fatty acids, fatty alcohols, beeswax, and vegetable oil. Apple pieces were coated with solutions or wrapped in preformed films. Changes in moisture content and color were measured during storage. Increasing concentrations of lipids significantly improved the moisture barrier properties of films. Water vapor permeability varied from 69 to 325 g mm/kPa d m². Apple-based wraps significantly reduced moisture loss and browning in fresh-cut apples. Color was preserved for 12 d at 5 °C. Wraps were significantly more effective than coatings.     

Highly stable, edible cellulose films incorporating chitosan nanoparticles

The need for biodegradable polymers for packaging has fostered the development of novel, biodegradable polymeric materials from natural sources, as an alternative to reduce amount of waste and environmental impacts. The present investigation involves the synthesis of chitosan nanoparticles-carboxymethylcellulose films, in view of their increasing areas of application in packaging industry. The entire process consists of 2-steps including chitosan nanoparticles preparation and their incorporation in carboxymethylcellulose films. Uniform and stable particles were obtained with 3 different chitosan concentrations. The morphology of chitosan nanoparticles was tested by transmission electron microscopy, revealing the nanoparticles size in the range of 80 to 110 nm. The developed film chitosan nanoparticles-carboxymethylcellulose films were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis, solubility tests, and mechanical analysis. Improvement of thermal and mechanical properties were observed in films containing nanoparticles, with the best results occurring upon addition of nanoparticles with 110 nm size in carboxymethylcellulose films. PRACTICAL APPLICATION: Carboxymethylcellulose films containing chitosan nanoparticles synthesized and characterized in this article could be a potential material for food and beverage packaging applications products due to the increase mechanical properties and high stability. The potential application of the nanocomposites prepared would be in packaging industry to extend the shelf life of products.     

蜂蜜对苹果酶促褐变的抑制及有效成分分析

作者以防止新鲜苹果切口的褐变为目标,比对不同食品配料组成的复配成分,发现蜂蜜作为涂膜材料可以有效延缓鲜切苹果片的褐变。将鲜切苹果片浸泡在质量分数0.1 g/g的椴树蜂蜜水溶液中,8 d后其仍能维持新鲜的色泽;探究了蜂蜜对苹果多酚氧化酶（polyphenol oxidase, PPO）抑制的动力学,发现蜂蜜对苹果PPO起非竞争性抑制作用,酶活抑制能力来自蜂蜜的抗氧化、清除自由基（相关系数r>0.6）能力;进一步分析蜂蜜成分与酶活抑制率的关系,发现蜂蜜中蛋白质与多酚（r值分别为0.79、0.63）是蜂蜜发挥抗褐变作用的重要成分。     

New strategies for minimally processed cactus pear packaging

This work presents a preliminary study on the packaging procedures to prolong the shelf life of minimally processed cactus pears. In particular, different packaging strategies were tested by combining coating and hydro-gels to different polymeric materials. Monitoring headspace gas concentrations, viable cell load of main spoilage microorganisms, sensory characteristics and weight loss, the quality decay in each packaging system was assessed. Results showed that the immersion of fresh-cut fruit into both hydro-gels strongly reduced the shelf life, most probably due to water migration from the surrounding hydro-gel to the crop. On the contrary, the coating prolonged the shelf life of the minimally processed fruit to about 13 days, corresponding to an increase of about 40%, compared to the control sample. Results also suggested that the barrier properties of the selected films did not affect greatly the quality of the coated fresh-cut produce.Industrial relevanceThe market of ready-to-eat fruit has grown rapidly in recent years. As a consequence, there is an emergent call for finding new preservation strategies to prolong the shelf life of minimally processed food, without compromising human and environmental safety. The results of this work dealing with minimally processed cactus pears represented an interesting goal with potential industrial applications. In fact, this paper combined the effectiveness of a natural coating applied to fresh-cut fruit to the performance of a bio-based polymeric packaging film.     

Postharvest Quality of Fresh-Cut Carrots Packaged in Plastic Films Containing Silver Nanoparticles

Active food packaging containing antimicrobial additive goes beyond traditional functions of packaging, once it can extend food shelf life maintaining its quality, safety and reducing postharvest losses by controlling food spoilage. Among several antimicrobial additives employed in polymeric films for packaging, metallic nanoparticles outstand due to its facility for synthesis, low-cost of production, and intense antimicrobial properties. In this work, extruded plain films of low-density polyethylene (LDPE) containing silver nanoparticles (AgNPs) embedded in SiO₂ and TiO₂ carriers (namely MS and MT, respectively) were produced and used as active packaging for maintaining the physicochemical and microbiological quality of carrots (Daucus Carota L. cv. Brasília). The neat (LDPE) and composite films containing MS and MT were characterized by scanning electron microscopy and permeability to oxygen and used for packaging fresh-cut sliced carrots stored at 10 °C for 10 days. After the storage time, the physicochemical properties of carrots were characterized, while the antimicrobial properties of films and AgNP migration were investigated. Our results revealed that both MT and MS packages showed antimicrobial activity even for films containing low concentration of AgNP. In addition, AgNP antimicrobial activity demonstrated to be carrier-dependent, once MT-LDPE showed improved performance compared to MS-LDPE. Regarding the physicochemical properties of packaged carrot, lower soluble solids and weight loss and higher levels of ascorbic acid were observed for carrots packaged with MT-LDPE films (compared to MS-LDPE), leading to a better postharvest quality conservation. Such differences observed in physicochemical properties of carrots are related to the distinct antimicrobial and film permeability properties for each composite film. In addition, under the conditions employed in this study, AgNP migration from the packages to fresh-cut carrot was not observed, which is highly desirable for food packaging safety, indicating the potential of such active packages for food preservation application.     

Development of user-friendly software for design of modified atmosphere packaging for fresh and fresh-cut produce

There is a wealth of published information on modified atmosphere packaging (MAP) but a lack of systematic treatment of the data in order to develop knowledge management systems that can provide information to users on which films to use for particular purposes and targets. This paper reports the development of user-friendly software for MAP design of fresh and fresh-cut produce. The software can select suitable packaging materials and define the amount of product to be packed or the area of the film that should be available for gas exchange. Two databases have been built in the software, which include recommended gas composition for 38 products, 75 respiration rate models, and permeability data for 27 polymeric films. This software was successfully tested for some products and an example for mango and Galega kale is described.Industrial relevanceThe PACKinMAP software selects the best possible film type for the given type of fresh or fresh cut fruit/vegetable. A manufacturer can type in a specific food product, such as a golden delicious apple, and the software will tell him the ideal type of packaging material according to the supplier or the retailer's needs. The software has also been found to simulate the package for any type of real-life distribution temperature history thus testing the ability of the package to withstand abuse.     

EFFECT OF PE/AG2O NANO‐PACKAGING ON THE QUALITY OF APPLE SLICES

ABSTRACT

Effects of low‐density polyethylene (LDPE) packaging and nano‐structured silver‐polyethylene (PE/Ag₂O) packaging on the overall sensory quality, color, weight and solute loss of fresh‐cut apples stored at 5 and 15C were studied in this research. Results showed that, compared with normal LDPE packaging, the PE/Ag₂O packaging helped to maintain the freshness of apple slices. Nano‐structured PE/Ag₂O bag delayed apple browning and decreased the weight loss of apple slices during storage. In addition, it can also prevent apple slices from microbial spoilage. As a result, the quality of apple slices saved at 5C in PE/Ag₂O bag was acceptable in 12 days, while those held in LDPE bag showed some deterioration in 6 days. Furthermore, considering the potential health risk resulting from silver leak, the safety of PE/Ag₂O bag was evaluated, and the result indicated an acceptable safety for food packaging.

PRACTICAL APPLICATIONS

Types of nano‐structured bags are recently commercialized for food packaging in many countries, but few documents report their performance in quality maintenance. This study indicates that nano‐structured PE/Ag₂O bag is effective in maintaining the freshness of apple slices with extended shelf‐life. Results of this work may be useful for promoting the acceptance and application of similar nano‐packaging in the quality maintenance of fresh‐cut products.     

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.     

Perspectives for chitosan based antimicrobial films in food applications

Recently, increasing attention has been paid to develop and test films with antimicrobial properties in order to improve food safety and shelf life. Active biomolecules such as chitosan and its derivatives have a significant role in food application area in view of recent outbreaks of contaminations associated with food products as well as growing concerns regarding the negative environmental impact of packaging materials currently in use. Chitosan has a great potential for a wide range of applications due to its biodegradability, biocompatibility, antimicrobial activity, non-toxicity and versatile chemical and physical properties. Thus, chitosan based films have proven to be very effective in food preservation. The presence of amino group in C2 position of chitosan provides major functionality towards biotechnological needs, particularly, in food applications. Chitosan based polymeric materials can be formed into fibers, films, gels, sponges, beads or even nanoparticles. Chitosan films have shown potential to be used as a packaging material for the quality preservation of a variety of food. Besides, chitosan has widely been used in antimicrobial films to provide edible protective coating, in dipping and spraying for the food products due to its antimicrobial properties. Chitosan has exhibited high antimicrobial activity against a wide variety of pathogenic and spoilage microorganisms, including fungi, and Gram-positive and Gram-negative bacteria. The present review aims to highlight various preparative methods and antimicrobial activity including the mechanism of the antimicrobial action of chitosan based films. The optimisation of the biocidic properties of these so called biocomposites films and role of biocatalysts in improvement of quality and shelf life of foods has been discussed.     

Physical Characterization and Pork Packaging Application of Chitosan Films Incorporated with Combined Essential Oils of Cinnamon and Ginger

Combinations of essential oils (EOs) can be an effective approach to reinforce their antimicrobial effects. In this sense, incorporation of two EOs into edible films may have supplementary utilizations in food packaging. Chitosan films containing combined EOs of cinnamon and ginger (1:1) at levels of 0.00, 0.05, 0.20, and 1.00% were developed and preliminarily characterized in the current study. The effect of the resulting materials on the antimicrobial and antioxidant properties of pork was then investigated during refrigerated storage (4 °C) over 9 days. Results showed that the presence of EOs markedly increased the thickness and opacity of the chitosan films, but did not modify the film solubility and water vapor permeability. When applied to the preservation of pork slices, these films were effective in retarding total microbial growth, increases in pH as well as lipid oxidation. The highest antioxidant and antimicrobial activities were observed in chitosan films incorporated with 1.00% EOs. These results suggest that chitosan-EO films have potential for application in pork packaging.     

Different packaging strategies for fresh-cut 'barattiere' melon cultivar (cucumis melo L.)

Optimising packaging for minimally processed 'Barattiere' melon cultivar ( Cucumis melo L.) is addressed in this work. Melon slices were dipped in water solution containing ascorbic acid (1%) and calcium chloride (0.2%). Dipped and untreated fresh-cut produce was packaged in four different polymeric materials (two biodegradable films, a commercially available multilayer film (MLF) and polypropylene), before storing at 5 °C. During storage, headspace gas composition, microbial quality, pH and mass loss were monitored for a period of 2 weeks. Results suggest that film characteristics strongly influenced gas concentrations in the headspace, microbial growth and weight. Among the tested packaging materials, the MLF seemed to delay significantly the detrimental phenomena involved in quality acceptance, even if clearly anaerobic atmospheres were recorded. The biodegradable films, combined with a dipping pre-treatment, could represent a good compromise between film performance and environmental impact.     

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.     

Polyphenoloxidase inactivation by light exposure in model systems and apple derivatives

The effect of UV-C and visible light on the enzyme polyphenoloxidase was studied in model systems and food. Enzyme inactivation under non thermal conditions was achieved following both UV-C and visible light exposure. UV-C light promoted enzyme inactivation in the entire range of irradiance and exposure time tested whilst visible light was effective only at high doses since lower intensity treatments were associated to enzyme activation. Polyphenoloxidase inactivation upon UV-C light exposure occurred as a consequence of protein aggregations other than those derived from thermal denaturation.The possibility to apply UV-C light exposure to achieve enzymatic stability of clear apple juice and fresh-cut apple slices was studied. Polyphenoloxidase inactivation in apple juice occurred to the detriment of natural occurring phenols which independently underwent photo oxidation. However, UV-C light exposure for few min prevented enzymatic browning during storage of refrigerated apple slices. The latter resulted comparable to the untreated apple slices from the sensory point of view.

Industrial relevance

Light irradiation is very effective in promoting polyphenoloxidase inactivation. UV-C light treatment has a good potential of successful application to achieve enzymatic stability in fresh-cut vegetables under non thermal conditions.