The effect of fatty acid content on water vapour and carbon dioxide transmissions of cellulose-based edible films

Water vapour and CO₂ transmissions of methyl cellulose (MC)-based edible films with varying amounts of the fatty acids, stearic acid (SA), palmitic acid (PA) and lauric acid (LA) were studied and the results were compared with those obtained for a film without added fatty acid. Water vapour transmission rate (WVTR), water vapour permeance (WVPN) and water vapour permeability (WVP) values of films were determined by measuring the amounts of water vapour transmitted through the film and then adsorbed on anhydrous CaCl₂ as a function of time, using a static method. A recently-developed static method which utilises ascarite to adsorb carbon dioxide transmitted through the film was employed for the determination of carbon dioxide transmission rate (CO₂TR), carbon dioxide permeance (CO₂PN) and carbon dioxide permeability (CO₂P) of films. Among the three fatty acids studied, SA was found to be the most effective in decreasing both the water vapour and the CO₂ transmissions of films. In general, it was observed that WVTR, WVPN and WVP values of films decreased with increasing fatty acid content in the film composition. CO₂ transmission parameters also decreased with increasing SA and PA contents but increased with increasing LA content of films.     

大麦醇溶蛋白/纳米TiO2可食性膜的制备与理化性质研究

本文以实验室自制的大麦醇溶蛋白为基材,以纳米TiO₂粒子为改性材料制备了可食性膜,并对其部分理化特性进行了深入研究。FTIR结果表明自制的蛋白粉在1654cm_-1、1545cm_-1及1452cm_-1处呈现典型的蛋白特征峰吸收;凯氏定氮结果表明其中蛋白含量高达92.63%;SDS-PAGE结果显示所制备的大麦醇溶蛋白主要包括大麦醇溶蛋白B组分(hordein B)及C组分(hordein C)。利用溶液浇铸法制备了大麦醇溶蛋白可食性膜以及大麦醇溶蛋白/纳米TiO₂可食性膜,并对两种膜的水蒸气透过率(透湿率)、透CO₂率、透O₂率、抗拉伸强度、断裂延伸率进行了对比研究。与大麦醇溶蛋白可食性膜相比,纳米TiO₂粒子的加入使得膜的平均透湿率降低了19.5%,平均透CO₂率、平均透O₂率分别提高了12.8%和17.1%,抗拉强度TS由313.91kPa提高至514.21kPa,断裂伸长率E由487%降低至221%。     

Potential Role of Pectate Lyase and Ca2+ in the Increase in Strawberry Fruit Firmness Induced by Short‐Term Treatment with High‐Pressure CO2

Postharvest treatment with high‐pressure CO₂ helps to control decay and increase firmness in strawberries. Increases in firmness occurred through modification of calcium binding to cell wall. However, the mechanism(s) involved in Ca²⁺ migration to pectic polymers and other physiological events associated with the maintenance of increased firmness are not clearly understood. The focus of this study was to find potential mechanism(s) that are associated with calcium movement, increases in firmness, or maintenance of firmness in strawberry fruit after high‐pressure CO₂ treatment. An increase in firmness was induced by high‐pressure CO₂ treatment, but not by high‐pressure N₂ treatment. This indicates that CO₂ stimulates a change in firmness. The increase in firmness induced by high‐pressure CO₂ seems to involve calcium efflux. Using membrane Ca²⁺‐dependent ATPase inhibitors sodium vanadate (250 μM) and erythrosin B (100 μM) delayed both the increase in firmness and calcium binding to wall polymers. Exogenous application of CaCl₂ (10 mM) enhanced the firmness increase of fruit slices only when they were exposed to high‐pressure CO₂. The activity of pectate lyase was downregulated by CO₂ treatment, but β‐galactosidase activity was not affected. The increase in strawberry firmness induced by high‐pressure CO₂ treatment primarily involves the efflux of calcium ions and their binding to wall polymers. These physiological changes are not induced by an anaerobic environment. The downregulation of wall‐modifying enzymes, such as pectate lyase, appeared to contribute to the maintenance of firmness that was induced by high‐pressure CO₂ treatment.     

Hydrogen and Calcium Ion Concentrations Affect Volume of CO2 Puffed Diced Green Bell Peppers

Diced green bell peppers were soaked in a solution of hydrochloric acid or calcium chloride, air-dried to 50% moisture, held in CO₂ at 5.8 MPa for 1, 3 or 5 min, and puffed by abruptly releasing the CO₂ pressure. Treatment with 1% CaCl₂ increased the size of puffed-dried products as compared to a control; however, HCl treatments did not. The treatment with 1 or 2% CaCl₂ reduced shrinkage as compared to the control. The 1% CaCl₂ treatment may have increased the CO₂ saturation rate.     

METHOD FOR MEASURING CO2 ABSORPTION IN CO2 and N2 PACKAGED FRESH MEAT1

Headspace gas composition of meat stored in modified atmosphere packaging (MAP) undergoes dynamic changes as a result of packaging film permeability, postmortem metabolic activity, CO₂ absorption in water and lipid, and bacteria growth and respiration. A combined analytical and experimental method was developed to investigate CO₂ absorption by packaged fresh meat in a gas-impermeable environment and during isothermal storage. the ideal gas law was used as a theoretical basis and a gas-impermeable and constant-volume chamber was constructed to evaluate the theoretical derivation. Changes in headspace pressure caused by dynamic interactions between beef and MAP atmospheres were monitored to predict concentration changes of CO₂ within the chamber. the proposed methodology for measuring CO₂ concentration changes was confirmed by gas analysis and proved valid for prediction of headspace CO₂ concentration changes in MAP gas-impermeable systems within the range of initial gas composition 20% to 100% CO₂ balanced with N₂, at temperatures ranging from 3 to 13C, and an initial headspace pressure of 155 kPa.     

An Edible Film of Lipids and Cellulose Ethers: Barrier Properties to Moisture Vapor Transmission and Structural Evaluation

An edible, composite film of lipid and cellulose ethers was developed and appraised as a barrier to moisture vapor transmission. The film was comprised of a matrix of methylcellulose, hydroxypropyl meth-ylcellulose and saturated C₁₆ and C₁₈ fatty acids, with a thin layer of white beeswax laminated to the surface. The edible film effectively retarded transport of moisture at water activities (a_w) up to at least 0.97 and maintained good barrier properties even when the a_w on the low-humidity side of the film was relatively high. The apparent activation energy for water vapor transmission through the edible film was 14.2 ± 2.5 kcal/mole. Electron microscopy revealed the importance of lipid morphology in determining moisture resistance lipid-base films.     

USE OF FLEXIBLE POLYMER MATERIAL FOR PACKAGING FRESH PEACHES

Fresh peaches (Prunus persica) were overwrapped in trays with 1 of 3 formulations of flexible polyvinyl chloride (PVC) film that differed in gas transmission rate or they were held in nonwrapped trays (controls). The CO₂ transmission rate at 0°C for PVC type III film was 280 mL/m^2. h (1 atmos); that of type II was 4 times greater and that of type I, about 5 times greater. The peaches were stored either 14 days at 0° or 7.5°C, or 7 days each at 0° and 7.5°C plus 2 days at 20°C to simulate retail display. The mean CO₂ levels were 10, 7.2 and 4.7% in packages that were wrapped with PVC III film and held at 7.5°, 0°/7.5° and 0°C, respectively. CO₂ in packages wrapped with PVC I or II was below 3% at each storage temperature. O₂ concentration remained about 4% in all packages. Weight loss was less and fruit was firmer among those packaged in PVC III than among nonwrapped controls at each of the 3 storage temperatures. Storage temperature had no effect on weight loss or of fruit held in PVC III film. External appearance of fruit packaged with the 3 types of film was significantly better than that of the controls. Internal appearance of the peaches was unaffected by any of the treatments. A microatmosphere favorable for fresh peaches can be maintained within packages overwrapped with polymer films that are selectively permeable to respiratory gases.     

氯化钙改性谷朊粉可食性复合膜的研究

本文研究了交联剂氯化钙对小麦谷朊粉复合膜性能的影响，应用综合评分法得出，氯化钙的最佳添加浓度为0．67％，此时综合得分为最高达120．99，在此条件下制得的复合膜，其拉伸强度提高了13．4％，水蒸气透过系数（WVP）降低了7．3％。应用氯化钙交联可以明显提高可食陛膜的强度，改善复合膜的机械幽抱。     

Effects of pH, CaCl2 and Soy Protein on [Ca2+] in Reconstituted Nonfat Dry Milk and on Rennet-Induced Coagulum Properties

Increasing CaCl₂ and lowering pH caused a significant increase in [Ca²⁺] in reconstituted nonfat dry milk (RNDM), while the addition of soy protein caused a significant reduction in [Ca²⁺]. Lowering pH greatly increased rennet-induced coagulum firmness in RNDM and slightly increased it in RNDM-soy protein mixtures. Added CaCl₂ increased coagulum textural parameters and syneresis in both systems. The extent to which these properties were increased was higher in RNDM than in the coagulum containing soy protein depending on the time after rennet addition and the amount of CaCl₂ added. The first increment of CaCl₂ added had the highest effect in improving textural properties and increasing syneresis.     

Tensile and water vapour properties of calcium‐crosslinked alginate‐cashew tree gum films

In this study, sodium alginate films were blended with cashew tree gum (CTG) and immersed in CaCl₂ solution. The influence of CTG concentration and immersion time in CaCl₂ on tensile properties, water vapour permeability and water solubility (WS) of alginate films was evaluated. Glycerol‐plasticized alginate/CTG films were cast on glass plates, which were then immersed in a 2% CaCl₂ solution to crosslink alginate. CTG concentration in the film solution and immersion time in CaCl₂ bath were varied according to a central composite design. Tensile strength, Young′s modulus, WS and water vapour barrier of the films were favoured by higher immersion times in CaCl₂ and lower CTG concentrations. The negative CTG effects on such properties have been attributed to competition between the polysaccharides for interactions with calcium ions, reducing crosslinking density and loosening the film structure. On the other hand, this loosening effect resulted in higher film flexibility at higher CTG concentrations.     

Prediction Equations for Gases in Flexible Modified-Atmosphere Packages of Respiring Produce are Different Than Those for Rigid Packages

Total pressure generally decreases in a sealed rigid package containing respiring produce, whereas total pressure is essentially constant and free volume decreases in a flexible package. We found that predicted O₂, CO₂, and N₂ partial pressures were different for similarly designed (same surface area, thickness, film permeabilities and produce mass) flexible and rigid packages at “quasi steady state” and steady state, respectively. Predicted O₂ and CO₂ partial pressures were slightly higher in a flexible package than in a rigid package and were a function of the film permeability ratio of N₂ to O₂ and of CO₂ to O₂. They also related to the ratio of product CO₂ production rate to O₂ uptake rate, target steady-state O₂ partial pressure, and respiration characteristics. Differences were slight for films such as low-density polyethylene.     

Evaluation of CO2 absorption and desorption rate in oysters (Cassostrea gigas) using the soluble gas stabilisation method

Soluble gas stabilisation (SGS) is a recently proposed method to extend the shelf life of food. However, no studies have determined the amount of carbon dioxide absorbed in food and particularly in oysters. Thus, the aim of this study was to determine CO₂ absorption and desorption rates in oysters during the solubilisation process. Cooked oysters were placed in the apparatus's chamber, CO₂ was injected into the chamber, and the SGS process started at different pressures, temperatures and gas/product (g/p) ratios. CO₂ absorption and desorption rates were obtained from data of CO₂ concentration in the chamber headspace and calculated by mathematical models. The results showed higher absorption rates under higher pressure, higher g/p ratio and lower temperature (0 °C). The concentration of CO₂ dissolved in the oysters was 21008.45 mg CO₂ kg product^?1. On the other hand, lower desorption rates occurred for the lowest pressure (200 kPa) and lowest gas/product ratio (1:1). For CO₂ desorption from oysters, it was observed that 10 min was enough to desorb a large amount of CO₂ under normal atmosphere.     

Effect of dietary modifications of calcium and magnesium on reducing solubility of phosphorus in feces from lactating dairy cows

Unintentional movement of P from dairy cow manure to off-farm locations has been an environmental concern for some time. The objective of this study was to evaluate the effects of increasing the dietary concentration and solubility of Ca and the dietary concentration of Mg on lactation performance and solubility of fecal P from lactating dairy cows receiving diets formulated to the same concentration of P (0.38% of dry matter). Eight dietary treatments were evaluated in a 2 × 2 × 2 factorial arrangement involving 2 dietary sources of Ca (CaCO₃ having a moderate solubility of Ca vs. CaCl₂ having an excellent solubility of Ca) and 2 dietary concentrations of Ca (average of 0.64 and 0.95% of dry matter) and Mg (0.25 and 0.4% of dry matter). Twenty-four multiparous cows in mid lactation were fed the 8 diets in three 21-d periods. Dry matter intake and milk production were measured daily, and milk composition was measured on the last 6 milkings of each period. Fecal samples were collected twice a day during the last 5 d of each period, composited within cow, dried at 55°C, and subjected to 10 successive water extractions, and soluble P, Ca, and Mg were determined. Excretion of fecal P (g/d) was correlated positively with intake of P but not with intake of Ca or Mg. A smaller proportion of fecal P was extracted when dietary concentration of Ca increased (37.5 vs. 47.7%) and when CaCl₂ instead of CaCO₃ was fed (40.3 vs. 44.9%). Feeding more Mg reduced water-soluble P in feces but only when CaCO₃ and not CaCl₂ was fed. Increasing the amount of soluble Ca in the diet produced a relatively stable Ca-phosphate compound (hydroxylapatite) in ashed fecal samples, whereas feeding less soluble Ca resulted in a more soluble P phase (Mg-substituted whitlockite). Energy-dispersive X-ray elemental spectroscopy in conjunction with scanning electron microscopy showed spatial association between Ca-Mg and P. A reduction of approximately 5 g of soluble P/cow per d was detected when dietary concentration of Ca increased from an average of 0.64 to 0.95% of dry matter. Supplemental CaCO₃ would be a preferred source of Ca over CaCl₂ because cows fed CaCO₃ tended to produce more 4% fat-corrected milk, more milk fat, and milk with a greater concentration of fat and protein. Current prices would also favor feeding CaCO₃ over CaCl₂. Increasing dietary intakes of Ca and Mg beyond current recommendations may increase formation of insoluble phosphate complexes (Ca-P rather than Ca-Mg-P associations), which result in decreased solubility of P in dairy-cow feces and reduce losses of P from agricultural areas where feces are applied.     

Optimization of processing of fresh‐cut pear

BACKGROUND: Successful processing of pears to render fresh‐cut fruits requires a thorough knowledge of their sensitivity to browning reactions, their respiratory metabolism, and their behaviour under modified atmosphere packaging. RESULTS: First, three different varieties of pear (Williams, Conference, Passacrassana) that had reached their commercial ripening stage were evaluated for suitability for minimal processing. Two antioxidant treatments were tested (treatment 1: 2% ascorbic acid + 1% citric acid + 1% CaCl₂; treatment 2: 2% ascorbic acid + 0.01% 4‐hexylresorcinol + 1% CaCl₂) to decide which one was the most effective against enzymatic browning. Finally, a modified atmosphere packaging was designed after two previous tests: measurement of respiratory activity of the peeled and cut pear at three temperatures (4, 15 and 25 °C); and evaluation of fruit tolerance to three different atmospheric compositions (21% O₂ + 10% CO₂; 2% O₂ + 0% CO₂; 2% O₂ + 10% CO₂). CONCLUSIONS: Conference pear was found to be the most suitable variety. Among the antioxidant treatments the one consisting of ascorbic acid, 4‐hexylresorcinol and CaCl₂ was proven to be the most effective against browning. The samples were packaged in a modified atmosphere with a composition of 10% O₂ + 10% CO₂ + 80% N₂. Copyright © 2008 Society of Chemical Industry     

Mechanical and physical properties of calcium-treated gellan films

The physicochemical properties of Ca²⁺-treated gellan films plasticized with glycerol were investigated as a function of CaCl₂ concentration (0–20%, w/w) in an aqueous soaking solution. Films were examined based on their mechanical properties, water vapor permeability (WVP), swelling index (SI), thickness and opacity. The SI was lower for Ca²⁺-treated films relative to a control, however, above 13% (w/w) CaCl₂ no differences in SI were found. At 13% (w/w) CaCl₂, tensile and puncture strengths reached a maximum. Tensile elongation, puncture deformation, film thickness and WVP were lower for CaCl₂-treated films than untreated, however, all increased with CaCl₂ concentration. Opacity of gellan films increased with the Ca²⁺-treatment relative to the untreated film, however declined as CaCl₂ concentration increased. In general, Ca²⁺-treated gellan films were stronger, acted as better water vapor barriers, swelled less when in contact with water, and became less pliable and transparent.     

Physical and mechanical properties of water resistant sodium alginate films

Properties of sodium alginate films were modified using two different methods of CaCl₂ treatment, i.e. the direct addition of CaCl₂ into film making solution (mixing films) and the immersion of alginate films into CaCl₂ solutions (immersion films), and their treatment effects on tensile strength (TS), percentage elongation at break (E), water vapor permeability (WVP), and water solubility (WS) of the films were investigated. TS and E of the mixing films were not changed considerably, but those of the immersion films changed considerably with significant (P<0.05) increase in TS and decrease in E. WVP of the immersion films decreased significantly (P<0.05), but that of the mixing films did not decreased. Water resistance measured by WS was not improved with the mixing films, but the alginate films became water resistant when they treated by immersing in higher than 2 g/100 ml CaCl₂ solutions. Water adsorption by the films also decreased in the immersion films. Swelling ratio (SR) of the immersion film decreased with temperature without affecting WS of the films.     

Extraction of sesame seed oil using supercritical CO2 and mathematical modeling

In this work, extraction of sesame oil from sesame seeds using supercritical CO₂ was carried out. The effect of operating parameters such as pressure, temperature, and supercritical CO₂ flow rate and particle size on extraction yield were investigated. An increase in the pressure and the supercritical CO₂ flow rate improved the extraction yield and also shortened the extraction time. The extraction yield increased as the particle size decreased depending on decreasing intraparticle diffusion resistance. The maximum extraction yield obtained was about 85% (relative to Soxhlet extraction by hexane) at 50 °C, 350 bar, 2 mL CO₂/min, 300–600 μm of particle size. Some extraction curves were modeled with two mathematical approaches as shrinking core model and broken and intact core model. The evaluation of model parameters showed that shrinking core model, however, is better than broken and intact cell model.     

Impact of Thermal and Chemical Pretreatments on Physicochemical,Rheological, and Functional Properties of Sweet Potato (Ipomea batatas Lam) Flour

The impact of thermal and chemical pretreatments on the physicochemical, rheological, and functional properties of sweet potato flour was investigated. The chemical pretreatment consisted in dipping peeled sweet potatoes in 1 % (w/v) calcium chloride (CaCl₂), while the thermal pretreatment was achieved by blanching them in tap water at 90 °C for 1 min. Composition in flour moisture, protein, fat, non-reducing sugars, and starch was determined using standard methods. Particle size, color, gelatinization, and rheological properties were analyzed. The water absorption index (WAI) and water solubility index (WSI), as well as the swelling capacity (SC) and sorption isotherms, were determined. The reducing sugar content of sweet potato flour was slightly higher in CaCl₂-pretreated (SSPCaCl₂) samples than that in blanched (SSPB) and control (SSP) samples. However, the lightness of the SSPB sample was lower than that of the SSPCaCl₂ and SSP samples. SSPCaCl₂ sample had the higher value of enthalpy of gelatinization and elasticity modulus G′. The SC was higher in blanched samples. A slight increase in the constant of water binding energy (C _BET) was observed after the CaCl₂ treatment and a marked increase for the blanched sample. Owing to the differences induced by blanching and CaCl₂ pretreatments, CaCl₂-pretreated flour samples are more suitable for bread-making processes and can also be used in food formulations.     

Study the kinetics and thermodynamics conditions for CO2 hydrate formation in orange juice concentration

In this study, for concentration of orange juice, two laboratory systems were used; one for CO₂ hydrate formation at high-pressure system, another for formation of THF hydrate at atmospheric pressure system. In the high-pressure system, the kinetic parameters of CO₂ hydrate formation in orange juice were investigated in comparison with pure water, in constant temperature and volume. Also the effect of the initial pressure (20, 30 and 35 bar), temperature (2, 3 and 4 °C) and brix (10, 13 and 16) were investigated on hydrate formation conditions. The results showed that, with increasing the pressure and lowering temperature, the initial rate of formation CO₂ hydrate is increased and the relaxation time is decreased. With increasing the brix, the initial rate of CO₂ hydrate formation is decreased and the relaxation time is increased. The maximum relaxation time of 1230 s was reached at 20 bar, 4 °C and 16 brix. It was determined that the content of orange juice plays as an inhibitor in hydrate formation. In the atmospheric system, the effect of brix (7, 10, 13, 16 and 20) on kinetics of THF hydrate formation was investigated in orange juice. After the separation of the formed crystals, the secondary brix was measured; the highest concentration in the initial brix of 7 was obtained about 200%., with increasing the brix, the induction time was increased, while it had no effect on the relaxation time.     

APPLE QUALITY AS INFLUENCED BY METHOD OF CaCl2 APPLICATION1

Pressurized CaCl₂ treatment of apple fruits enhanced storage quality of both ‘Golden Delicious’ and ‘Lord Lambourne’ apples. Calcium dip treated apples were similar in storage quality to untreated apples. Apple fruits that were pressure treated with CalCl₂ were firmer than calcium dip treated or untreated apples. Calcium treatment, either pressure or dip treated, reduced pH and total browning. Quality parameters were influenced more by CaCl₂ at the first harvest than in a subsequent harvest.