Water Vapor Transmission Rates and Sorption Behavior of Chitosan Films

ABSTRACT: This study measured the water vapor transmission rates (WVTR) and moisture sorption of chitosan films over a range of water vapor pressures at 25 °C. Films of a constant thickness were made using chitosan with 3 levels of deacetylation. Films were tested at test relative humidity (RH) difference between RH values of 84%, 75%, 69%, 53%, 43%, 33%, 23%, 11%, and 0 at 25 °C using ASTM F1249-90 or ASTM E 96-80. The equilibrium moisture content in the films ranged from 3.7% to 31.8% (dry basis) corresponding to 11% to 84% RH. WVTRs of films increased with increase in water vapor pressure. The mean WVTR ranged from 6.7 to 1146 (g/m²/d) over the range of water vapor pressure from 2.68 (11% RH) to 19.9 mmHg (84% RH). The percentage of deacetylation of chitosan films and the viscosity of the cast solution did not have an effect on the WVTR properties of chitosan films.     

马铃薯泥和面对挂面品质的影响

使用马铃薯熟泥代替水和面制作小麦粉挂面、全麦粉挂面、糙米粉挂面、糙小米挂面、玉米粉挂面、白高粱挂面、红高粱挂面、豌豆粉挂面、甜荞粉挂面、苦荞粉挂面10种挂面,分析马铃薯熟泥对挂面的色泽、蒸煮品质、感官品质和质构品质的影响,探讨马铃薯熟泥提高挂面品质的作用.结果表明:使用马铃薯泥能够提高花色挂面的表面L*值,降低a*值,...     

基于DMA和DSC分析技术研究马铃薯泥面条特性

为深入探讨马铃薯泥、水和食盐添加量对马铃薯泥面条形成机理的影响,采用动态力学分析法和差式量热扫描法进行单因素实验并分析。结果表明,添加马铃薯泥可降低面条刚性、导致马铃薯泥面条吸热焓变的增加和非冻结水含量的下降,从而降低马铃薯泥面条的品质;水的添加量,增加非冻结水的含量,使马铃薯泥面条更加筋道,提高了面条的整体品质;面条中适当地添加食盐,有助于提高面条的弹性和粘性。     

甘薯泥对面团流变特性及馒头品质的影响

利用粉质仪、拉伸仪、质构仪和色差计研究甘薯泥对面团流变特性及馒头品质的影响。结果表明,随着甘薯泥添加量的增加,面团吸水率、面团形成时间、稳定时间及粉质指数逐渐降低,弱化度增加;面团的拉伸曲线面积、拉伸阻力、拉伸比增大,延伸度降低,且醒发时间越长,其变化趋势越大。与白面馒头相比,甘薯泥的加入使馒头的比容、感官评分降低,胶黏性增大,馒头的亮度下降,色泽变暗,馒头具有浓郁的甘薯香味。     

马铃薯泥面条制作工艺优化及品质分析

为保留马铃薯的风味和营养成分,提高面条品质,加快马铃薯主食化进程,采用马铃薯泥和小麦面粉复配制作马铃薯泥面条。以感官评分为评价指标,结合单因素实验和正交试验,进而得到较优的马铃薯泥面条加工工艺。结果表明,在马铃薯泥占比50%的条件下,面条的较佳加工工艺参数为:面团醒发温度20 ℃、醒发时间30 min。复配改良剂最佳配方为:谷朊粉添加量3%、魔芋粉添加量1%、单甘酯添加量1%。该条件下制作的马铃薯泥面条品质较好,感官评分达90.1分。研究表明,在小麦面粉中加入马铃薯泥,所制备面条品质降低,但适当的添加改良剂可在一定程度上提升马铃薯泥面条品质。     

果胶酶酶解预处理对马铃薯泥干燥特性及生粉加工特性的影响

为提高马铃薯生粉的干燥效率,考察了果胶酶酶解预处理不同时间(60~180min)对马铃薯泥热风干燥特性及制备的酶解马铃薯生粉(pectinase-treated native potato flour,PNPF)理化性质和加工特性的影响。结果表明:果胶酶酶解处理降低了马铃薯泥果胶含量和初始含水量,提高了薯泥干燥速率,干燥时间缩短了6.32%~7.81%;果胶酶酶解预处理制备的生粉中果胶、灰分、蛋白质含量显著降低,直链淀粉、支链淀粉和总淀粉含量显著提高,淀粉相对结晶度和生粉碘蓝值降低;同时酶解预处理制备的生粉与未处理生粉相比,具有较高的溶解度和溶胀度,持油性显著降低,持水性提高了40.49%~49.58%,冻融析水率降低了26.23%~62.11%,其中酶解预处理180min制备的生粉(PNPF180)冻融稳定性提升幅度最大;糊化特性分析结果表明,PNPF峰值温度降低,峰值时间缩短,崩解值上升,最终黏度和回生值下降。果胶酶酶解预处理可改善马铃薯泥热风干燥特性,缩短干燥时间,同时显著改善马铃薯生粉基本理化性质及加工特性。     

The Effect of Freezing Conditions on the Quality of Freeze-Chilled Reconstituted Mashed Potato

Freeze-chilling involves freezing and frozen storage of food products followed by thawing and chilled retail display. The objective of this trial was to examine the effect of different freezing conditions (−30 °C, −60 °C, −90 °C) on selected quality parameters of freeze-chilled reconstituted potato flakes. Lowering the freezing temperature reduced the time required for freezing, gave a softer product and led to a reduction in drip loss. Freeze-chilling resulted in a firmer product and a higher drip loss compared to chilling alone. There was no difference in vitamin C content or in taste panel acceptability between the chilled and the freeze-chilled products.     

纳米纤维素材料氧气与水蒸气阻隔性能的研究现状

纳米纤维素主要来源于植物纤维,具有比表面积高、强度高、密度低、透明性高、热膨胀低等特点,其特有的形态结构和表面性能使得纳米纤维素材料可以形成致密的网络结构进而提供优良的阻隔性能。本综述就纯纳米纤维素膜、纳米纤维素复合材料以及纳米纤维素涂布纸基材料重点讨论了纳米纤维素材料氧气与水蒸气阻隔性能的研究现状,以探讨纳米纤维素应用于包装材料的可能性。     

高直链玉米淀粉-壳聚糖复合膜透气透水性能研究

本文以高直链玉米淀粉(HACS)和壳聚糖(CS)为基本材料,甘油为增塑剂,甲基纤维素(MC)为增强剂制备可食性复合膜,研究了高直链玉米淀粉与壳聚糖的配比、甘油的添加量以及甲基纤维素的添加量对复合膜的透气透水性能的影响.结果表明,HACS:CS为2:1时,膜的CO2透过量和O2透过量最低,水蒸气透过量(WVT)也处于较低...     

Mathematical Model for Perforation Effect on Oxygen and Water Vapor Dynamics in Modified-Atmosphere Packages

A mathematical model was developed to study the influence of film perforations on O₂ concentration and relative humidity in the atmosphere in a package containing fresh fruits. The model included equations describing fruit respiration and transpiration as well as permeation of oxygen and water vapor through the perforated film. Closed-system experiments with mango fruit revealed a linear dependence of respiration rate on O₂ concentration. The model allowed analytical computation of the time course of in-package O₂ concentration and relative humidity, and the results were in good agreement with experimentally measured values. Perforations had a much more pronounced effect on O₂ concentration than on relative humidity. The model enabled practical predictions for designing modified-atmosphere packaging.     

Sensory and Texture Properties of Mashed Potato Incorporated with Inulin and Olive Oil Blends

The effect of adding different ratios of inulin and extra virgin olive oil blends, formulated without (MPA) and with cryoprotectants (MPB), on texture properties of fresh mashed potatoes and frozen/thawed mashed potatoes was studied. Inulin and extra virgin olive oil behaved like soft fillers, but inulin was associated with increased fibrousness and extra virgin olive oil with increased creaminess. In the total dataset and frozen mashed potatoes, frozen/thawed mashed potatoes, and MPA subgroups, component 1 was a contrast between mechanical and surface textural attributes, whereas in MPB samples component 1 was determined by geometrical attributes. Addition of inulin at 30 g/kg and extra virgin olive oil at 45 g/kg is recommended.     

Vitamin C Stability during Preparation and Storage of Potato Flakes and Reconstituted Mashed Potatoes

High performance liquid chromatography with electrochemical detection was used to follow losses of L-ascorbic acid (AsA) in the processing and serving of fortified mashed potatoes. Cumulative losses of AsA were: 56% for adding AsA to freshly mashed potatoes at 251 ppm (wet basis); 82% drum-drying the potatoes; 82% storing the flakes 4.3 months at 25°C., and 96% reconstituting mashed potatoes and holding them 30 min on a steam table. The mashed potatoes at the point of ingestion would contain 10 ppm AsA (wet basis), and one serving size (100g) would provide 2% of the adult RDA. Fortification with equivalent levels of magnesium L-ascorbate 2-mono-phosphate (AsMP) or sodium L-ascorbate 2-polyphosphate (AsPP) gave overall cumulative losses of 20 or 32%, respectively. Such reconstituted mashed potatoes contained 201 ppm and 171 ppm AsA respectively, and one serving would provide about 33% of the RDA of vitamin C.     

不同温湿度对奶粉包装膜水蒸气透过率的影响

主要研究了不同温度(25~38℃)和湿度(RH35%~90%)对奶粉包装膜的水蒸气透过率的影响。试验结果表明,该奶粉包装膜在一定相对湿度时,水蒸气透过率随温度的升高而升高;在一定温度时,水蒸气透过率随相对湿度的升高而升高;温度越高,相对湿度越大,该奶粉包装膜的水蒸气透过率越大。     

壳聚糖/蜂蜡改善纸基材料水蒸气和氧气阻隔性能研究

围绕壳聚糖(CS)和蜂蜡(Wax)在改善纸基材料气体(水蒸气和氧气)阻隔性能方面开展研究,探讨了蜂蜡添加量及其与壳聚糖的复合方式(共混和分层)对纸基材料阻隔性能和涂层热稳定性能的影响。结果表明,涂布纸的水蒸气透过量随蜂蜡添加量的增加而降低,当蜂蜡添加量为15%时,在50%RH (相对湿度)条件下,分层涂布纸和共混涂布纸的水蒸气透过量分别降至21.87和24.13 g/(m²·d),与纯壳聚糖涂布纸相比,分别降低了80.3%和78.2%,分层涂布纸与共混涂布纸的水蒸气透过量差异不大;在75%RH条件下,分层涂布纸(163.69 g/(m²·d))和共混涂布纸(242.24 g/(m²·d))的水蒸气透过量与纯壳聚糖涂布纸相比,分别降低了79.4%和69.5%,而与共混涂布纸相比,分层涂布纸的水蒸气透过量降低了32%。共混涂布纸和分层涂布纸的氧气透过量随着蜂蜡添加量的增加而增大,当蜂蜡添加量为15%时,分层涂布纸和共混涂布纸的氧气透过量仍低至70.19和101.75 cm³/(m²...     

NaCl添加量及pH对马铃薯泥品质特性的影响

该试验以蒸制熟化的马铃薯泥为对象,利用电子眼、应变控制流变仪、物性测试仪、扫描电子显微镜、激光共聚焦显微镜、X-射线衍射仪、核磁共振分析系统等,研究NaCl添加量（0%、0.5%、1.0%,m/m,以薯泥计）及pH（6、7、8）对马铃薯泥色泽、流变学特性、质构特性及微观结构等的影响规律。结果表明：随NaCl添加量的增加,马铃薯泥弹性由81.86%减小到79.40%、硬度由551.72 g增大到784.28 g,网络结构受到一定的破坏。随pH的增加,与pH为6时相比,马铃薯泥的弹性由81.44%减小到75.96%、硬度呈先降低后升高的趋势,稳定性减弱;当pH为6时,马铃薯泥弹性最大（81.44%）,硬度较小（528.84 g）,形成了致密的凝胶网络结构。综上所述,在不添加NaCl、pH为6时,马铃薯泥具有最佳的加工特性。该研究可为采用NaCl及调节pH制备适用于主食及休闲食品加工的高品质马铃薯泥提供理论依据。     

Permeability and Diffusivity of d-Limonene Vapor in Polymeric Sealant Films

The permeability (P) and Diffusivity (D) of d-limonene vapor in nine polymeric sealant films were measured and compared at a vapor concentration of 0.719 mg/L over the range 25–45°C. The sorption of d-limonene (q_s) was determined by a temperature programmed desorption (TPD) method. Equations to predict P and D for the different films were derived as a function of q_s or temperature (T_mp) of differential scanning calorimeter measured melting points (DSCmp) of the films. Results indicated a tendency of test films with smaller values of q_s and higher T_mp to have higher barriers against loss of d-limonene due to absorption.     

浸水处理对鲜切马铃薯抗氧化能力的影响

分别将鲜切马铃薯片以不同的料液比1∶1、1∶2、1∶3、1∶4(g/mL)放入水中分别浸泡0、5、10、15、30 min后置于5℃下贮藏1 d～12 d,研究浸水处理时间和料液比对鲜切马铃薯抗氧化能力的影响。结果表明,与其他浸水处理时间相比,浸水15 min能显著(P0.05)抑制鲜切马铃薯的褐变速度,而料液比对鲜切马铃薯的褐变速度无显著影响。进一步的抗氧化能力试验表明15 min浸水处理能够降低脂氧合酶(lipoxygenase,LOX)活性和丙二醛(malondialdehyde,MDA)含量,提高超氧化物歧化酶(superoxide dismutase,SOD)的活性以及Mn-SOD和Fe-SOD表达量,增加脯氨酸含量以及吡咯啉-5-羧酸合成酶(pyrroline-5-carboxylate-synthetase,P5CS)和吡咯啉-5-羧酸还原酶(pyrroline-5-carboxylate-reductase,P5CR)的表达量,增强鲜切马铃薯的抗氧化能力,从而维持鲜切马铃薯在贮藏期间的感官品质并延长货架期。     

酶解马铃薯泥对馕质构和风味的影响

将不同比例的马铃薯泥(MP)、α-淀粉酶酶解马铃薯泥(α-AMP)和β-淀粉酶酶解马铃薯泥(β-AMP)分别与小麦粉复配制作馕,对比分析了不同类型马铃薯泥对馕质构和风味的影响.结果表明,随着MP或α-AMP添加量增加,馕内部的气孔逐渐减少,其质构品质变差;而添加β-AMP的馕内部保留了均匀气孔,添加10％或15％β-A...     

乙醇熏蒸处理对鲜切莲藕片褐变和活性氧代谢的影响

褐变是导致鲜切莲藕品质劣变的重要因素,本文选用150μL/L乙醇熏蒸处理鲜切莲藕2 h,研究乙醇对其酶促褐变和活性氧代谢的影响。结果表明,经过10℃下贮藏12 d后,与对照组相比,乙醇处理后的鲜切藕片褐变度降低了6.49%,L*值提高了21.44%。乙醇处理也能通过抑制苯丙氨酸解氨酶和多酚氧化酶活力来抑制鲜切莲藕酚类物质的合成及氧化。在贮藏末期,对照组的可溶性醌含量是乙醇处理组的1.15倍。此外,乙醇处理可有效维持过氧化氢酶和过氧化物酶活性和抗坏血酸含量。经过12 d的贮藏后,乙醇处理后的鲜切莲藕的O₂^-·生成速率和H₂O₂积累分别是对照组的87.69%和79.17%。综上,乙醇熏蒸处理可能通过抑制酚类物质代谢,提高抗氧化能力,从而延缓鲜切莲藕褐变的发生。     

壳聚糖/聚乙烯醇改善纸基材料的水蒸气和氧气阻隔性能研究

研究了壳聚糖和聚乙烯醇在改善纸基材料水蒸气(极性气体)和氧气(非极性气体)阻隔性能上的应用效果,探讨了壳聚糖/聚乙烯醇不同质量比和不同复合方式(共混和分层)对纸基材料水蒸气和氧气阻隔性能、机械性能和涂层稳定性的影响。结果表明,随着壳聚糖和聚乙烯醇质量比的降低,纸基材料的水蒸气阻隔性能逐渐增强,同时氧气阻隔性能逐渐降低;壳聚糖/聚乙烯醇分层涂布纸的水蒸气和氧气透过量均低于壳聚糖/聚乙烯醇共混涂布纸。当壳聚糖和聚乙烯醇的质量比为1∶1时,壳聚糖/聚乙烯醇分层涂布纸的水蒸气透过量和氧气透过量分别为9.36 g/(m~2·d)和31.93cm~3/(m~2·d);与纯壳聚糖涂布纸相比,水蒸气透过量降低了约92%,与壳聚糖/聚乙烯醇共混涂布纸相比,水蒸气透过量降低了约68%,氧气透过量降低了约67%。