Mechanical and water vapor permeability properties of biodegradables films based on methylcellulose, glucomannan, pectin and gelatin

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Mimic biological structures such as the cell wall of plant tissues may be an alternative to obtain biodegradable films with improved mechanical and water vapor barrier properties. This study aims to evaluate the mechanical properties and water vapor permeability (WVP) of films produced by using the solvent-casting technique from blended methylcellulose, glucomannan, pectin and gelatin. First, films from polysaccharides at pH 4 were produced. The film with the best mechanical performance (tensile strength = 72.63 MPa; elongation = 9.85%) was obtained from methylcellulose-glucomannan-pectin at ratio 1:4:1, respectively. Then, gelatin was added to this polysaccharide blend and the pH was adjusted to 4, 5 and 6. Results showed significant improvement in WVP when films were made at pH 5 and at polysaccharides/gelatin ratio of 90/10 and 10/90, reaching 0.094 and 0.118 g.mm/h.m(2).kPa as values, respectively. Films with the best mechanical properties were obtained from the blend of polysaccharides, whereas WVP was improved from the blend of polysaccharides and gelatin at pH 5.313739746PEC-PGConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Stability of free and immobilized Lactobacillus acidophilus and Bifidobacterium lactis in acidified milk and of immobilized B-lactis in yoghurt

This study evaluated the stability of Bifidobacterium lactis (Bb-12) and of Lactobacillus acidophilus (La05) both free and immobilized in calcium alginate, in milk and in acidified milk (pH 5.0,4.4 and 3.8). The stability of immobilized B. lactis in yoghurt (fermented to pH 4.2), during 28 days of refrigerated storage was also evaluated. The efficiency Of two Culture media (modified MRS agar and Reinforced Clostridial Agar plus Prussian Blue) for counting of B. lactis ill yoghurt was determined. Lee's agar was used to count Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus when B. lactis were counted in the MRS medium. B. lactis and L. acidophilus in both free and immobilized forms presented satisfactory rates of survival ill milk and acidified milk because the average reduction of the Population was only one log cycle after 21 days of storage. The number of viable cells of immobilized B. lactis in yoghurt presented a gradual decline throughout the storage period, passing from 10(8) cfu/ml to no Count after 28 days of storage. When the Cultures were not in equilibrium just the selective medium was efficient in counting B. lactis ill yoghurt. The results showed that both microorganisms call be added to milk and acidified milk, because their population was only slightly affected during storage. The presence of traditional culture of yoghurt seems to be harmful for Survival of immobilized B. lactis and the immobilization in calcium alginate failed as an effective barrier to protect the cells in all analysed treatments.354167115115

Encapsulation of Blackberry Anthocyanins by Thermal Gelation of Curdlan

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Blackberry shows an attractive color due to the presence of anthocyanins; however the use of these pigments as natural colorant is difficult since some external agents, specially pH>3, cause their discoloration. On the other hand, encapsulation techniques have been widely used in the industry to protect active ingredients. The aims of this study were to establish the encapsulation conditions of anthocyanins from blackberry, to evaluate the capsules characteristics, as well as the anthocyanins release. Three polysaccharides (curdlan, pectin and sodium alginate) were evaluated as wall material to obtain capsules by gelation. Curdlan was chosen since it was the only gum capable to form hard gel under low pH value. The capsules showed spherical form and multinucleated appearance, and encapsulation efficiency ranged from 80.3 to 96.7%. The release curves followed first order kinetics, with a strong burst effect, 80 to 100% of the anthocyanins released in solution at pH 1 after 20 min.201019081915Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

The stability of ascorbic acid microencapsulated in granules of rice starch and in gum arabic

Ascorbic acid (AA) was microencapsulated by spray drying, using gum arabic and rice starch as covering materials. The AA was dissolved in solutions of the wall material prior to processing. For the rice starch, gelatin was used as a binding agent and recovery was effected with calcium pectate. The morphology of the materials was analysed by optical and scanning electron microscopy, it thus being possible to verify the formation and evaluate the structural characteristics of the microcapsules. The capsules produced with gum arabic were smaller (d(50%) = 8.0 mu m) and with a multimode particle size distribution, whilst uncovered starch capsules containing 1-2% gelatin presented a distribution mainly in the range of 5-40 mu m. The capsules recovered with calcium pectate had average diameters 10-15 times greater than those obtained only by spray drying. The stability of the encapsulated materials was studied at room temperature (RH 60-65%) and at 45 degrees C (RH 60-65% and 90.7%). AA microencapsulated in gum arabic was shown to be as stable as free crystalline AA under environmental conditions, whereas that encapsulated in rice starch was less stable. Increasing the amount of the binding agent gelatin increased the stability of the uncovered starch encapsulated AA. Recovery with calcium pectate notably increased the stability of the starch encapsulated AA, as compared to the uncovered samples.17216917

The effect of the immobilisation of Lactobacillus acidophilus and Bifidobacterium lactis in alginate on their tolerance to gastrointestinal secretions

This research aimed at evaluating the "in vitro" tolerance of Bifidobacterium lactis and Lactobacillus acidophilus, both free and immobilised in calcium alginate, to pH and bile levels similar to those encountered in the human stomach and intestine, respectively. Free and immobilised cultures were inoculated, at the level of 10%, into HCl solutions with pH values of 1 and 2, and then incubated anaerobically at 37 degrees C, being subsequently plated out at intervals of 0, 1 and 2 h after incubation. The bile concentrations tested were 0, 2 and 4%. Counts were made by the pour plate method using MRS broth after 0 and 12h of anaerobic incubation. Morphological observations of the cells immobilised in alginate gel were made using a scanning electron microscope. The cell counts of samples containing alginate drops were effected after solubilisation in 2% sodium citrate using a Stomacher homogeniser. A pH value of 2 promoted a slight decline in the number of viable microorganisms and pH 1 was extremely deleterious for both B. lactis and L. acidophilus, the same effect being shown for the cells immobilised in alginate. inoculation into bile did not affect the stability of B, lactis and L. acidophilus. Thus B. lactis and L. acidophilus showed intolerance to pH 1 and immobilisation in alginate was not effective in protecting their cells.55949649

Cashew gum microencapsulation protects the aroma of coffee extracts

Microencapsulation of materials rich in volatile compounds by spray drying presents the challenge of removing water by vapourization without loss of odour and/or flavour components. Crioconcentrated coffee extracts rich in odour components were used as a substrate core to evaluate microencapsulation with cashew gum from Anacardium occidentale L. In Brazil, cashew gum is a low cost alternative to the traditional Arabic gum. A suspension containing coffee extract and the wall material was dissolved in water and then passed through a spray dryer. Core microcapsules were microwave-assisted extracted (MAE) and the aroma protection of the microcapsules produced was evaluated using gas chromatography and mass spectroscopy (GC/MS). The external morphology and size distribution of the microcapsules were obtained by scanning electron microscopy (SEM) and light scattering techniques, respectively. When comparing Arabic and cashew gum microencapsulation of coffee extracts both wall materials were observed to have similar aroma protection, external morphology and size distribution. Sensory analysis was employed to examine flavour protection and consumer preference with microencapsulation. These biochemical, sensory and structural data suggest that low cost cashew gum is a well suited alternative for odour microencapsulation to the more costly Arabic gum currently used in Brazil.251132

Proteolysis and functional properties of mozzarella cheese as affected by refrigerated storage

Each of three cheese batches was randomly divided into two parts, one was subjected to slow freezing for 15 days and the other maintained under refrigeration. Thereafter the cheeses were tempered under refrigeration for 1 mo and evaluated weekly. In general, cheeses presented low melting capacity as a result of low levels of proteolysis, This low intensity of proteolysis was probably a function of the destruction of the lactic starter and partial inactivation of the coagulant during stretching of the cheese. Free oil content increased during storage for both treatments, but more in the tempered samples.64220220

Effect of edible wheat gluten-based films and coatings on refrigerated strawberry (Fragaria ananassa) quality

Edible coatings and films can provide an alternative for extending the postharvest life of fresh fruits and vegetables. The effect of different wheat gluten-based coatings and films on refrigerated strawberry quality and shelf life was studied. Coatings were formed directly on the surface of the fruit and films were previously formed (on Teflon surfaces) and then used to pack fruit. Fruit quality was evaluated by weight loss, firmness retention, visible decay, surface color development, titratable acidity, total soluble solids, reducing sugar content and a sensory evaluation. The bilayer coating of wheat gluten and lipids (beeswax, stearic and palmitic acids) had a significant effect on the retention of firmness, reduced the weight loss and showed better results from the physico-chemical analysis compared to the control fruit. All the treatments with gluten film (except with the film pouch) also showed a beneficial effect on firmness retention compared to the control fruit. The gluten film (except the film wrap) seemed to be more promising for controlling decay than the coatings. Sensory evaluation of the strawberries showed that the gluten and the composite coatings maintained the visual quality of the fruit during the storage time, and the taste of the strawberries with the gluten coating was acceptable to consumers. However, the appearance and taste of the bilayer-coated fruit were unacceptable. © 2004 Elsevier B. V. All rights reserved.36219920

Microencapsulation of L-acidophilus (La-05) and B-lactis (Bb-12) and evaluation of their survival at the pH values of the stomach and in bile

Microcapsules were prepared using the probiotic microorganisms Lactobacillus acidophilus (La-05) and Bifidobacterium lactis (Bb-12) and the spray drying technique and cellulose acetate phthalate as the wall material. This study evaluated the resistance of these microorganisms to drying at three temperatures and also the in vitro tolerance of the free and microencapsulated form to pH values and bile concentrations similar to those found in the human stomach and intestine. With an air entry temperature of 130 degreesC and exit temperature of 75 degreesC, the number of viable cells of B. lactis was practically unaltered, whereas the population of L. acidophilus was reduced by two logarithmic cycles. B. lactis was more resistant to the drying process than L. acidophilus under all conditions tested. The morphology of the microcapsules was determined by scanning electron microscopy and the microcapsules presented a rounded external surface containing concavities, a continuous wall with no apparent porosity, average size of 22 mum, moisture content varying from 5.3 to 3.2% and water activity between 0.230 and 0.204. After inoculation into HCl solutions with pH values adjusted to 1 and 2, incubated anaerobically at 37 degreesC, and plated after 0, 1 and 2 h of incubation, microcapsules were effective in protecting the microorganisms, while the populations of both free microorganisms were eliminated after only 1 h at the acidic conditions. Microencapsulated B. lactis and L. acidophilus, both free and microencapsulated, were also resistant after 12 h to bile solutions.19448549

Effect of sugar and sorbitol on the formation of low methoxyl pectin gels

Pectin gels were made with amidated low methoxyl pectin using sucrose, glucose, fructose and sorbitol as sweetening agents. The adsorption of water at controlled activity was measured by determining sorption isotherms and by differential scanning calorimetry. These results were correlated with the gel formation mechanism. H-1 NMR spectra were measured for sugar with and without Ca2+ or La3+ cations. Results demonstrated no correlation between water adsorption on sugars and gel rigidity. The effects of the different sugars appear to be associated with the competition between each sugar and the pectin for calcium cations. (C) 2000 Elsevier Science Ltd. All rights reserved.41442142