Fabrication of hydrophobic and high-strength packaging films based on the esterification modification of galactomannan.

There is an increasing interest in substituting current packaging films with biologically-derived films without compromising mechanical properties and hydrophobicity. In this work, the esterified galactomannan (E-GM) films with good hydrophobicity, excellent oxygen barrier performance and high tensile mechanical strength were synthesized using anhydride esterification method prior to film formation. The hydrophobicity, mechanical properties, barrier properties, thermal stability and ultraviolet absorption of the prepared films were determined to fully investigate the features of galactomannan-based films. The results indicated that GM films can be successfully obtained by esterification. Compared to neat GM film, E-GM-1.5 film (acetic anhydride to GM of 1.5:1) achieved the highest degree of esterification (0.05), hydrophobicity (107°) and mechanical strength (92.0 MPa). In addition, the esterified GM films had lower toxicity for macrophages cells. The prepared E-GM films may provide more opportunities for further advancement and applications in the development of food packaging from natural resources.

Effects of UV-C irradiation and traditional thermal processing on acemannan contained in Aloe vera gel blends.

The effects of pH (3.5, 4.5, and 5.5) and UV-C irradiation dose (12.8, 24.2, 35.8, and 54.6 mJ/cm2) on the physicochemical properties changes in 10% Aloe vera gel blends; in addition, the acemannan concentration and structural changes in the precipitated polysaccharides were evaluated. A thermal treatment (TT; 45 s at 90 °C) was used for comparison. In contrast to TT, a dose of 24.2 mJ/cm2 did not induce significant changes of free sugar content. Moreover, TT and UV-C irradiation did not significantly affect the content of mannose but increased those of galactose, fructose, and glucose. 1H NMR analysis revealed minimal changes in the isolated fractions of acemannan, indicating that compared to the unprocessed control sample, the acemannan deacetylation was more pronounced by TT (27%) than by UV-C irradiation (11% at 54.6 mJ/cm2), without any significant difference between the two. UV-C irradiation of Aloe vera gel blends at pH 3.5 and 24.2 mJ/cm2 was an alternative to TT and efficiently preserve the characteristics of acemannan.

Effect of gamma irradiation on the physicochemical and structural properties of plant seed gums.

The objective of the study was to evaluate the effect of irradiation (0-5 kGy) on the physicochemical properties of two seed gums (guar and locust bean gum). The Hunter color parameters changed upon irradiation, namely "L" value decreased, whereas "a" and "b" values, i.e. redness and yellowness, increased. Irradiation reduced the final viscosity of gums at neutral and acidic pH. Increase in irradiation dose (0-5 kGy) increased the water absorption in the range of 11.75-14.61g/g and 20.04-23.99g/g in guar gum and locust bean gum, respectively. Rheological study of the gums revealed their gel behaviour with higher values of G' than G". G' in native guar gum was observed to increase in the range of 880.39-1332.29Pa while G" increased in the range of 194.21-239.77Pa as the test frequency was raised from 14.6-100s-1. In native locust bean gum, the G' and G" varied in the range of 476.50-1230.50Pa and 300.65-380.30Pa, respectively, under the applied frequency sweep. FT-IR revealed the presence of CH, COOH and CO groups in the guar as well as locust bean gum, in addition to the uronic acid and pyranose rings. The absorption of the functional groups declined upon irradiation.

Physicochemical properties of peanut protein isolate-glucomannan conjugates prepared by ultrasonic treatment.

Peanut protein isolate (PPI) was glycated with glucomannan through classical heating or ultrasound treatment in this work. The physicochemical properties of PPI-glucomannan conjugates prepared by ultrasound treatment were compared to those prepared by classical heating. Compared with classical heating, ultrasound treatment could accelerate the graft reaction between PPI and glucomannan and improve the concentration of available free amino groups of PPI. Solubility and emulsifying properties of the conjugates obtained by ultrasound treatment were both improved as compared to those obtained by classical heating and native PPI. Decreases of lysine and arginine contents during the graft reaction indicated that these two amino acid residues attended the covalent linkage between PPI and glucomannan. Structural feature analyses suggested that conjugates obtained by ultrasound treatment had less α-helix, more ß-structures and random coil, higher surface hydrophobicity and less compact tertiary structure as compared to those obtained by classical heating and native PPI.

Radiation dose dependent change in physiochemical, mechanical and barrier properties of guar gum based films.

Mechanical and water vapor barrier properties of biodegradable films prepared from radiation processed guar gum were investigated. Films prepared from GG irradiated up to 500 Gy demonstrated significantly higher tensile strength as compared to non-irradiated control films. This improvement in tensile strength observed was demonstrated to be due to the ordering of polymer structures as confirmed by small angle X-ray scattering analysis. Exposure to doses higher than 500 Gy, however, resulted in a dose dependent decrease in tensile strength. A dose dependent decrease in puncture strength with no significant differences in the percent elongation was also observed at all the doses studied. Water vapor barrier properties of films improved up to 15% due to radiation processing. Radiation processing at lower doses for improving mechanical and barrier properties of guar based packaging films is demonstrated here for the first time.

Irradiation depolymerized guar gum as partial replacement of gum Arabic for microencapsulation of mint oil.

Spray dried microcapsules of mint oil were prepared using gum Arabic alone and its blends with radiation or enzymatically depolymerized guar gum as wall materials. Microcapsules were evaluated for retention of mint oil during 8-week storage during which qualitative changes in encapsulated mint oil was monitored using principal component analysis. The microcapsules with radiation depolymerized guar gum as wall material component could better retain major mint oil compounds such as menthol and isomenthol. The t(1/2) calculated for mint oil in microcapsules of gum Arabic, gum Arabic:radiation depolymerized guar gum (90:10), gum Arabic:enzyme depolymerized guar gum (90:10) was 25.66, 38.50, and 17.11 weeks, respectively. The results suggested a combination of radiation depolymerized guar gum and gum Arabic to show better retention of encapsulated flavour than gum Arabic alone as wall material.

Effect of ultrasound on enzymatic acylation of konjac glucomannan.

A comparative study was made of enzymatic acylation of konjac glucomannan with vinyl esters under ultrasonic irradiation and shaking in organic solvent tert-butanol. Among the 13 enzymes selected, Novozym 435 exhibited the highest acylation activity towards KGM whether under ultrasonic irradiation or shaking. The application of ultrasonic irradiation instead of shaking during the acylation led to improvement in the initial reaction rate, yield and degree of substitution of the modified KGM. Appropriate ultrasound power (100 W) and water activity (0.75) were found to accelerate enzymatic reaction. The acceleration effect of ultrasound on Novozym 435-catalyzed acylation decreased with an increase in the chain length of the acyl donors from C2 to C18. Moreover, the acylation of KGM in tert-butanol was proved to be a regioselective one, with C6-OH being acylated. Compared with shaking, ultrasound did not change regioselectivity of Novozym 435 in the acylation.

Heat or gamma irradiation sterilization affects the hypocholesterolemic effect of guar gum in axenic and heteroxenic rats.

1. Twenty-two axenic (germfree) or thirty heteroxenic (axenic colonized with human flora) 2.5-3.5 months old female Fisher rats were fed for four weeks either a hypercholesterolemic (HYPER) diet or a HYPER diet containing 5% guar gum (GG) sterilized by heat or by gamma irradiation. 2. Axenic rats fed the irradiated GG diet had higher cholesterolemia than their counterparts fed an autoclaved diet (4.50 vs 2.29 mmol/l), whereas the method of sterilization had no effect on plasma cholesterol in axenic HYPER or heteroxenic animals (7.35 vs 6.51 mg/dl). 3. The levels of hepatic esterified cholesterol were higher in heteroxenic animals fed the irradiated GG diet than in their counterparts fed the autoclaved GG diet (5.65 vs 3.57 mmol/g tissue). 4. The composition of volatile fatty acids in the cecal content of heteroxenic rats was dependent on the method of sterilization regardless of the presence of fiber: the levels of butyrate were 2.88 and 0.85 mumol/g for rats fed the autoclaved and irradiated diets, respectively. 5. Gamma irradiation abolished the cholesterol-lowering effect of guar gum, whereas sterilization by heat preserved this effect. 6. The hypocholesterolemic effect of guar was reduced by gamma irradiation sterilization and was probably mediated by qualitative changes in the intestinal microflora which interfered with bile acid absorption.

Heat or gamma irradiation sterilization affects the hypocholesterolemic effect of guar gum in axenic and heteroxenic rats

1. Twenty-two axenic (germfree) or thirty heteroxenic (axenic colonized with human flora) 2.5-3.5 months old female Fisher rats were fed for four weeks either a hypercholesterolemic (HYPER) diet or a HYPER diet containing 5 per cent guar gum (GG) sterilized by heat or by gamma irradiation. 2. Axenic rats fed the irradiated GG diet had higher cholesterolemia than their counterparts fed an autoclaved diet (4.50 vs 2.29 mmol/l), whereas the method of sterilization had no effect on plasma cholesterol in axenic HYPER or heteroxenic animals (7.35 vs 6.51 mg/dl). 3. The levels of hepatic esterified cholesterol were higher in heteroxenic animals fed the irradiated GG diet than in their counterparts fed the autoclaved GG diet (5.65 vs 3.57 mmol/g tissue). 4. The composition of volatile fatty acids in the cecal content of heteroxenic rats was dependent on the method of sterilization regardless of the presence of fiber: the levels of butyrate were 2.88 and 0.85 mumol/g for rats fed the autoclaved and irradiated diets, respectively. 5. Gamma irradiation abolished the cholesterol-lowering effect of guar gum, whereas sterilization by heat preserved this effect. 6. The hypocholesterolemic effect of guar was reduced by gamma irradiation sterilization and was probably mediated by qualitative changes in the intestinal microflora which interfered with bile acid absorption

Effect of gamma irradiation, penicillin, and/or pectic enzyme on chick growth depression and fecal stickiness caused by rye, citrus pectin, and guar gum.

The effects of gamma irradiation of rye, corn, pectin, and guar gum and supplementation of procaine penicillin and/or pectic enzyme (Irgazyme-100) were studied. Addition of 62.5% rye, 4% pectin, or 2% guar gum in place of corn significantly reduced chick growth (P < .05). Exposure to gamma irradiation, procaine penicillin, or pectic enzyme supplementation improved the growth of chicks fed rye. Growth response on the rye diet to one or more combinations of gamma irradiation, procaine penicillin, and pectic enzyme was greater than that of gamma irradiation, procaine penicillin, or pectic enzyme alone. Gamma irradiation or pectic enzyme supplementatin of pectin or guar gum improved chick growth and almost eliminated their growth depressing properties. A combination of gamma irradiation and pectic enzyme failed to give a further significant increase in growth over that of either alone. Addition of procaine penicillin to diets containing rye, irradiated pectin, or guar gum elicited a significant growth response, but the response was greatly reduced when diets contained irradiated guar gum or irradiated pectin. Feces of chicks fed diets containing rye, pectin, or guar gum adhered to screen floors in much greater amounts than for corn-fed chicks. Gamma irradiation, procaine penicillin, or pectic enzyme had no significant effect on fecal condition of birds fed diets containing rye or guar gum. In contrast, fecal condition of birds fed guar gum was significantly improved by a combination of gamma irradiation and pectic enzyme supplement. Gamma irradiation almost eliminated and pectic enzyme supplementation completely eliminated properties of pectin causing sticky feces. Results indicate that the component of rye that causes sticky feces was not changed by gamma irradiation and/or pectic enzyme, and, therefore, is different from the growth depressing factor and from citrus pectin.