响应面法优化桑葚酵素食用凝胶的制备工艺

以海藻酸钠、壳聚糖、桑葚酵素为原料,氯化钙为离子交联剂,制备酵素食用凝胶。通过单因素实验和Box-Behnken响应面法,研究海藻酸钠与壳聚糖质量比、交联时间、氯化钙浓度对酵素凝胶硬度、胶着性、咀嚼性等质构指标的影响。结果表明,酵素凝胶最佳的制备工艺为:海藻酸钠与壳聚糖质量比5:2.82、交联时间131 min、氯化钙浓度17.9 mg/mL。在此优化工艺条件下,测得酵素凝胶硬度为7.19 N、胶着性为6.60 N、咀嚼性为0.70 kgf。优化所得结果准确可靠,可为酵素功能性食品的进一步开发与利用提供理论依据和技术参考。     

Structure evolution of pullulan–alginate edible films during drying studied by low‐field NMR

The evolutions of spatial structure for pullulan, alginate, and pullulan–alginate blend aqueous solutions during drying were investigated by low‐field nuclear magnetic resonance. For pullulan solutions, during the first 1,320 min of drying, NMR signal intensity in profiles did not vary with position. Thereafter, the apparent shift of the air–pullulan interface began at 1,440 min, indicating the onset of progressive shrinkage of pullulan samples. Similar shrinkage phenomena were observed for alginate and pullulan–alginate blend solutions. In contrast, spatial structural heterogeneity was observed for alginate solution during drying time from 1,200 to 1,560 min, due to the formation of a skin layer near the air–alginate interface. Based on the change of polymer solutions during drying, two‐stage evaporation process was detected in the aqueous pullulan, alginate, and their blend solutions. Moreover, the evaporation rate of water during the second stage of drying was significantly lower than that of the first stage.

Practical applications

Edible films have emerged as an alternative to synthetic petroleum‐based polymers for food packaging. The evolutions of spatial structure of pullulan–alginate solutions during drying were studied by monitoring of their NMR profiles. Information shown in this study would provide some scientific basis for studying film‐forming mechanism of edible films and their applications in the food field.     

Physical and antibacterial properties of edible films formulated with apple skin polyphenols

Fruit and vegetable skins have polyphenolic compounds, terpenes, and phenols with antimicrobial and antioxidant activity. These flavoring plant essential oil components are generally regarded as safe. Edible films made from fruits or vegetables containing apple skin polyphenols have the potential to be used commercially to protect food against contamination by pathogenic bacteria. The main objective of this study was to evaluate physical properties as well as antimicrobial activities against Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica of apple skin polyphenols at 0% to 10% (w/w) concentrations in apple puree film-forming solutions formulated into edible films. Commercial apple skin polyphenol powder had a water activity of 0.44 and high total soluble phenolic compounds and antioxidant capacity (995.3 mg chlorogenic acid/100 g and 14.4 mg Trolox/g, respectively). Antimicrobial activities of edible film containing apple skin polyphenols were determined by the overlay method. Apple edible film with apple skin polyphenols was highly effective against L. monocytogenes. The minimum concentration need to inactive L. monocytogenes was 1.5%. However, apple skin polyphenols did not show any antimicrobial effect against E. coli O157:H7 and S. enterica even at 10% level. The presence of apple skin polyphenols reduced water vapor permeability of films. Apple skin polyphenols increased elongation of films and darkened the color of films. The results of the present study show that apple skin polyphenols can be used to prepare apple-based antimicrobial edible films with good physical properties for food applications by direct contact.     

海藻酸钠凝胶机制及其在食品中的应用研究进展

海藻酸钠作为一种天然多糖,具有良好的功能特性,在食品中得到普遍应用.生产实践中主要使用钙盐制备水凝胶,凝胶形成的网络结构可以提高食品特性.它的形成受到海藻酸钠的浓度、结合钙离子浓度、温度、pH值等因素的影响.海藻酸钠凝胶在食品应用领域中备受关注,尤其是在微囊化、可食性膜、质地改良等方面应用广泛.     

Advances in Edible Coatings for Fresh Fruits and Vegetables: A Review

Edible coatings are an environmentally friendly technology that is applied on many products to control moisture transfer, gas exchange or oxidation processes. Edible coatings can provide an additional protective coating to produce and can also give the same effect as modified atmosphere storage in modifying internal gas composition. One major advantage of using edible films and coatings is that several active ingredients can be incorporated into the polymer matrix and consumed with the food, thus enhancing safety or even nutritional and sensory attributes. But, in some cases, edible coatings were not successful. The success of edible coatings for fresh products totally depends on the control of internal gas composition. Quality criteria for fruits and vegetables coated with edible films must be determined carefully and the quality parameters must be monitored throughout the storage period. Color change, firmness loss, ethanol fermentation, decay ratio and weight loss of edible film coated fruits need to be monitored. This review discusses the use of different edible coatings (polysaccharides, proteins, lipids and composite) as carriers of functional ingredients on fresh fruits and vegetables to maximize their quality and shelf life. This also includes the recent advances in the incorporation of antimicrobials, texture enhancers and nutraceuticals to improve quality and functionality of fresh-cut fruits. Sensory implications, regulatory status and future trends are also reviewed.     

Food preservative content reduction by controlling sorbic acid release from a superficial coating

In the aim to reduce the total amount of preservatives added in food, edible coating is used in the present study as surface retention of active agents to maintain a local high effective preservative concentration where microorganisms are intended to contaminate and/or grow, i.e. on coating surface. A food/anti-microbial coating system with sorbic acid as the active compound, agar gel as model food and wheat gluten (WG) or beeswax (BW) film as edible coatings was studied. A mathematical model able to describe the release kinetics of the anti-microbial agents from the edible coating into food products was developed and validated. It was used for estimating the local surface concentration in sorbic acid of coated model food. This surface concentration is an essential value for predicting microorganism growth but cannot be evaluated by experiments. In the case of WG coating, the surface concentration drops below 10% of the initial value after 1 h whereas in the case of the BW coating, the surface concentration remains above 75% even after one week of contact. Simulation realized using the estimated surface concentration and a simplified equation for the growth inhibition kinetics of Saccharomyces cerevisiae were compared to microbiological efficacy assessment. The calculated amount of sorbic acid required to maintain a 0.2% surface concentration during 23 days was 100 times lower when introducing the additive in a beeswax thin layer than directly in the core of the high moisture food or in a hydrophilic film such as wheat gluten.Industrial relevanceThe methodology presented in this study based on experimental measurements and mathematical predictions is of great interest for the rational design of anti-microbial coatings and could be used in industrial applications. Edible coatings are already used in commercial practice for their barrier properties (water barrier property for example to avoid remoistening or drying of cereal-based products, gas barrier properties for the coating of fresh fruits and vegetable, etc) or for food appearance improvement (brilliance of apples for examples could be improved using polysaccharide-based film). Edible coatings have proved to be suitable as vector of preservatives such as anti-microbial or anti-oxidants. By using such retention matrices, very small amount of additives is required since the preservative is concentrated at the product surface. The benefit of using anti-microbial edible coating for consumer health is consequently non-negligible and this aspect is more and more taken into account by food manufacturers. The use of active edible coatings at an industrial scale is expected to grow, in Europe, due to the European framework regulation (EC 2004/1935) which authorizes the concept of active packaging with intentional active agents' release.The efficacy of anti-microbial edible coating could be assessed through time-consuming experimental tests. But most of the time, the couple edible matrix/active compound suitable for one applicable won't be anymore suitable for another food product and empirical tests should be undertaken once more by the food manufacturer. By using an integrated approach such as the one presented in this work, based on mathematical model for predicting additive release kinetics, numerous experiments may be avoided, since once the preservative diffusivity values in the coating and the food are known, the numerical tool could be used to optimize the initial quantity of preservative to add in the coating, to predict the food shelf life as a function of coating thickness or coating concentration in preservative, etc. The data shown in this paper concerning wheat gluten- and beeswax-based films could be also added in data bases of industrial relevance for further commercial applications.The approach used in this study could be considered as an assistant and prediction tool that should (i) optimize food preservation and (ii) help manufacturers in elaboration of new food product and packaging.     

可食膜的研究进展

可食膜是指由可食性材料形成的膜,主要通过防止气体、水汽和溶质等的迁移来保证食品的质量,延长食品的货架期。可食膜作为一种新型包装材料,具有绿色环保、生物降解、无毒无害、能够提高食品的保质期和提高食品的质量等优点,而且还具有营养价值。因此,近年来国内外对可食膜的研究越来越多,可食膜的应用范围也越来越广。我们日常生活中包装糖果使用的糯米纸、包装冰激凌使用的蛋筒、包装肉菜使用的豆腐皮和包装肉馅使用的肠衣等都是典型的可食性包装。根据可食膜的制备材料不同,本文对多糖类可食膜、蛋白质可食膜、脂质可食膜和复合型可食膜这几种常用的可食膜进行了综述,分别介绍了这几种可食膜的研究状况。并根据近几年来国内外研究进展,对可食膜在果蔬和肉类中的应用进行了叙述。     

Fungal Inactivation by Mexican Oregano (Lippia berlandieri Schauer) Essential Oil Added to Amaranth,Chitosan, or Starch Edible Films

ABSTRACT: Edible films can incorporate antimicrobial agents to provide microbiological stability, since they can be used as carriers of a wide number of additives that can extend product shelf life and reduce the risk of pathogenic bacteria growth on food surfaces. Addition of antimicrobial agents to edible films offers advantages such as the use of low antimicrobial concentrations and low diffusion rates. The aim of this study was to evaluate inhibition of Aspergillus niger and Penicillium spp. by selected concentrations of Mexican oregano (Lippia berlandieri Schauer) essential oil added to amaranth, chitosan, or starch edible films. Oregano essential oil was characterized by gas chromatography-mass spectrometry (GC/MS) analysis. Amaranth, chitosan, and starch edible films were formulated with essential oil concentrations of 0%, 0.25%, 0.50%, 0.75%, 1%, 2%, and 4%. Mold radial growth was evaluated inoculating spores in 2 ways: edible films were placed over inoculated agar, Film/Inoculum mode (F/I), or the edible films were first placed in the agar and then films were inoculated, Inoculum/Film mode (I/F). The modified Gompertz model adequately described growth curves. There was no significant difference (P > 0.05) in growth parameters between the 2 modes of inoculation. Antifungal effectiveness of edible films was starch > chitosan > amaranth. In starch edible films, both studied molds were inhibited with 0.50% of essential oil. Edible films added with Mexican oregano essential oil could improve the quality of foods by controlling surface growth of molds.     

Inactivation of Listeria monocytogenes on ham and bologna using pectin-based apple, carrot, and hibiscus edible films containing carvacrol and cinnamaldehyde

Edible films can be used as wrapping material on food products to reduce surface contamination. The incorporation of antimicrobials into edible films could serve as an additional barrier against pathogenic and spoilage microorganisms that contaminate food surfaces. The objective of this study was to investigate the antimicrobial effects of carvacrol and cinnamaldehyde, incorporated into apple, carrot, and hibiscus-based edible films against Listeria monocytogenes on contaminated ham and bologna. Ham or bologna samples were inoculated with L. monocytogenes and dried for 30 min, then surface wrapped with edible films containing the antimicrobials at various concentrations. The inoculated, film-wrapped samples were stored at 4 °C. Samples were taken at day 0, 3, and 7 for enumeration of surviving L. monocytogenes by plating on appropriate media. Carvacrol films showed better antimicrobial activity than cinnamaldehyde films. Compared to control films without antimicrobials, films with 3% carvacrol induced 1 to 3, 2 to 3, and 2 to 3 log CFU/g reductions on ham and bologna at day 0, 3, and 7, respectively. Corresponding reductions with 1.5% carvacrol were 0.5 to 1, 1 to 1.5, and 1 to 2 logs, respectively. At day 7, films with 3% cinnamaldehyde reduced L. monocytogenes population by 0.5 to 1.5 and 0.5 to 1.0 logs on ham and bologna, respectively. Inactivation by apple films was greater than that by carrot or hibiscus films. Apple films containing 3% carvacrol reduced L. monocytogenes population on ham by 3 logs CFU/g on day 0 which was 1 to 2 logs greater than that by carrot and hibiscus films. Films were more effective on ham than on bologna. The food industry and consumers could use these films to control surface contamination by pathogenic microorganisms. PRACTICAL APPLICATION: Antimicrobial edible, food-compatible film wraps prepared from apples, carrots, and hibiscus calyces can be used by the food industry to inactivate Listeria monocytogenes on widely consumed ready to eat meat products such as bologna and ham. This study provides a scientific basis for large-scale application of edible fruit- and vegetable-based antimicrobial films on foods to improve microbial food safety.     

Characterization of Edible Active Coating Based on Alginate–Thyme Oil–Propionic Acid for the Preservation of Fresh Chicken Breast Fillets

Chicken meat presents serious problems of processing and storage. Edible coatings are used commercially to improve the shelf life of fresh foods. The aim of this study is to develop an effective antimicrobial edible coating to improve the shelf life and safety of fresh chicken meat. The effect of propionic acid and thyme essential oils as antimicrobial and antioxidant compounds incorporated into alginate‐based edible coating was evaluated. Physical, antimicrobial and sensorial analyses were performed in coated and uncoated samples. Sensorial analysis showed no significant differences between coated and uncoated samples, which do not influence the buying decisions of consumers. The pH of the meat surface, color and sensorial analysis changed during storage time, showing similar behavior between coatings, the principal parameters to determine the shelf life of this product were weight loss and microbiological deterioration, where coatings had different behaviors. The selected coating increased the shelf life by about 33% with the lowest dehydration.     

含精油可食性抗菌膜研究进展

可食性抗菌膜是目前食品包装领域研究的重要方向,含精油可食性抗菌膜是其研究的热点之一。本文介绍含精油的可食性食品包装膜中精油的主要成分及其抗菌特性,概述此类膜的一般制备技术,对含精油膜抗菌的抗菌性能测试方法进行归纳,就精油对可食性膜抗氧化性、机械性能、渗透性及其他理化性能的影响作重点阐述,最后分析含精油可食性抗菌膜可能存在的问题,并预测其发展前景。     

Moisture Loss and Lipid Oxidation for Precooked Ground-Beef Patties Packaged in Edible Starch-Alginate-Based Composite Films

Edible films of starch‐alginate (SA), starch‐alginate‐stearic acid (SAS), SA‐tocopherol, SAS‐tocopherol, tocopherol‐coated SA film, and tocopherol‐coated SAS film were evaluated for their effectiveness in maintaining quality of precooked beef patties stored at 4 °C. Patty weight loss, moisture loss, 2‐thiobarbituric acid‐reactive substances value, the formation of hexanal, pentane, and total volatiles of samples differed with film composition. SAS‐based films were more effective (P < 0.05) in controlling moisture loss than lipid oxidation. Tocopherol‐treated films were more effective (P < 0.05) in inhibiting lipid oxidation than were nontocopherol films. Most of the tested edible films were not as effective as polyester vacuum bags in retarding moisture loss and lipid oxidation.     

Edible Films and Coatings as Carriers of Living Microorganisms: A New Strategy Towards Biopreservation and Healthier Foods

Edible films and coatings have been extensively studied in recent years due to their unique properties and advantages over more traditional conservation techniques. Edible films and coatings improve shelf life and food quality, by providing a protective barrier against physical and mechanical damage, and by creating a controlled atmosphere and acting as a semipermeable barrier for gases, vapor, and water. Edible films and coatings are produced using naturally derived materials, such as polysaccharides, proteins, and lipids, or a mixture of these materials. These films and coatings also offer the possibility of incorporating different functional ingredients such as nutraceuticals, antioxidants, antimicrobials, flavoring, and coloring agents. Films and coatings are also able to incorporate living microorganisms. In the last decade, several works reported the incorporation of bacteria to confer probiotic or antimicrobial properties to these films and coatings. The incorporation of probiotic bacteria in films and coatings allows them to reach the consumers’ gut in adequate amounts to confer health benefits to the host, thus creating an added value to the food product. Also, other microorganisms, either bacteria or yeast, can be incorporated into edible films in a biocontrol approach to extend the shelf life of food products. The incorporation of yeasts in films and coatings has been suggested primarily for the control of the postharvest disease. This work provides a comprehensive review of the use of edible films and coatings for the incorporation of living microorganisms, aiming at the biopreservation and probiotic ability of food products.     

响应面试验优化玉米淀粉-壳聚糖可食膜的制备工艺

通过响应面法优化玉米淀粉、壳聚糖和甘油的质量分数来制备可食膜,以机械性能（伸长率、抗拉强度）和透湿性（water vapor permeability,WVP）为评价指标,得出二次响应预测模型。结果表明：玉米淀粉、壳聚糖和甘油的质量分数分别为3.71%、0.95%和0.64%时,抗拉强度最大;3 种物料质量分数分别为3.82%、0.50%和1.00%时,伸长率最大;3 种物料质量分数分别为3.52%、0.52%和0.50%时,WVP最小。综合考虑,玉米淀粉、壳聚糖和甘油质量分数分别为3.50%、0.50%和0.67%时,可食膜的性能最优。     

Bioactive edible films for food applications: mechanisms of antimicrobial and antioxidant activity

Abstract

In order to improve the quality of food and to extend their shelf life, a new generation of active edible films is being especially intended after the incorporation of organic acids, enzymes, antimicrobial proteins, phenolic compounds, or other functional ingredients such as probiotics, flavors, vitamins and nutraceuticals. These active compounds have different mechanisms of action related to their structure, their concentration, the nature of micro-organism targeted, the process of encapsulation or incorporation in the biopolymer film-networks. The application of the active films by direct contact or indirect contact via the head space also affects the bioactivity of these compounds. This article critically reviews the published work on active edible-films and their applications for food preservation. The classes of active compounds and their action mechanisms are firstly discussed. Then, an extended overview on their effect on model food (simulants) or on real food during storage was also addressed. Edible films offer two main advantages over the direct incorporation of the antimicrobial or antioxidant agents into the bulk food: 1) to control the diffusion of active compounds at the surface of the food and 2) to reduce the amount of preservatives added in the food.     

Review characterization of edible films formulated with sodium alginate and low-methoxyl pectin in osmotic dehydration applications

The aim of this work was to evaluate the behaviour of two edible films (sodium alginate and low-methoxyl pectin) under different osmotic conditions (solutions: sucrose, glucose syrup and maltodextrin; concentrations: 40 °Brix and 60 °Brix; temperature 40 °C and processing times: 0.5, 1 and 2 h). From the experimental water loss and solid uptake kinetics, effective diffusion coefficients and the dehydration performance ratio were obtained. The microstructural characteristics of the osmodehydrated films were also analysed using pear as a food matrix. The results showed that films osmodehydrated with maltodextrin and glucose syrup solutions presented higher dehydration performance ratio values than those osmodehydrated with sucrose. A reduction in the thicknesses of edible coatings was observed. The best formulation was sodium alginate 2% and calcium lactate 5% according to the microstructural analysis and structural integrity for at least up to 16 h of osmotic dehydration.     

玉米磷酸酯淀粉秸秆纤维素可食膜的制备及物理性能

以玉米磷酸酯淀粉（corn distarch phosphate,CDP）和玉米秸秆纤维素（corn straw cellulose,CSC）为主要基材制备可食膜。研究CDP与CSC质量比、羧甲基纤维素（carboxymethyl cellulose,CMC）质量浓度、丙三醇（glycerol,Gly）质量浓度对可食膜物理性能抗拉强度（tensile strength,TS）、断裂伸长率（elongation at break,EAB）、水蒸气透过系数（water vapour permeability,WVP）和透光率的影响。在此基础上以可食膜的物理性能综合分为响应值,采用响应面法优化制备工艺参数。结果表明：最佳工艺条件为CDP-CSC质量比8.5∶1.5、CMC质量浓度0.8 g/100 mL、Gly质量浓度1.0 g/100 mL,此条件下可食膜物理性能综合分最高为0.683,对应可食膜的TS为19.75 MPa、EAB为46.89%、WVP为1.167×10－12 g/（cm•s•Pa）、透光率为41.86%,比未添加CSC的CDP膜物理性能综合分提高27.14%。通过扫描电子显微镜、X射线衍射和傅里叶变换红外光谱分析对可食膜进行结构观察和表征,表明CDP/CSC可食膜表面较平整,结构致密,各基质相容性好。     

Physical and Antioxidant Characterization of Edible Films Added with Red Prickly Pear (<Emphasis Type="Italic">Opuntia ficus-indica</Emphasis> L.) cv. San Martín Peel and/or Its Aqueous Extracts

The aim of this research was to investigate the effect of the addition of peel powder and/or its aqueous extract on physical and antioxidant characteristics of carboxymethyl cellulose (CMC) edible films. Prickly pear peel powder and aqueous extract (2 and 4%) were characterized in color, bioactive compounds (betalains and total phenolic compounds), antioxidant capacity and reducing power. Edible films were prepared with CMC, glycerol, varying the dissolution medium (0, 2, or 4% aqueous extract from prickly pear peel) and peel powder (0, 1, or 2%) using a face-centered central composite design. Physical, mechanical, bioactive compounds, and antioxidant capacity properties were investigated in edible films. Prickly pear peel powder presented 58.8 ± 0.08 mg of betacyanins/100 g, 53.8 ± 0.2 mg of betaxanthins/100 g, 967.8 ± 20 mg Gallic acid equivalent (GAE)/100 g for total phenolic compounds, an antioxidant capacity equivalent to 420.9 ± 4.9 mg GAE/100 g and a reducing power of 879.1 ± 115.9 mg ascorbic acid equivalent (AAE)/100 g. High concentration of aqueous extract and peel powder in CMC films increased the bioactive compounds content, antioxidant capacity and reducing power. Films mechanical properties were not affected by the aqueous extract; nevertheless, were strongly affected by the peel powder. Response surface methodology was used to optimize edible films formulation with high antioxidant characteristics, being the optimal formulation 1.7% of peel powder plus 3.3% of aqueous extract. This study may be the base for exploitation of prickly pear peel as source of bioactive compounds with antioxidant capacity for their use in edible coatings.     

Edible films with anti‐Listeria monocytogenes activity

Edible films based on wheat gluten, gelatin and brea gum were prepared with incorporation of ca. 500 UA cm^?2 of enterocin with anti‐Listeria monocytogenes action, synthesised by Enterococcus faecium CRL1385. The analyses of the different edible films revealed that they did not show any significant changes in their functional and physicochemical features after the enterocin incorporation (P value < 0.05). Gelatin and brea gum films had a higher solubility in water than wheat gluten films. Listeria cell growth were not inhibited by edible matrices per se; while a similar inhibition to that of free enterocin was observed in gelatin films after 2 h and remained unchanged for the duration of the assay. Wheat gluten films showed a lower enterocin–matrix interaction and a limited bactericidal action was observed for 2 h, after which the activity disappeared. In contrast, brea gum was found to interact with the enterocin molecule inhibiting its anti‐Listeria activity. Edible gelatin and wheat gluten films with enterocin can be potentially used to control Listeria monocytogenes contamination in food products.