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Different strategies to produce thermoplastic materials using starch and zein were studied, aiming to investigate their effect on the compatibility of starch and zein. Research strategies comprised the use of two different plasticizers for starch, two different compatibilizing agents, and two blending procedures. The plasticizers were mixtures of sorbitol and glycerol (SG) or urea and formamide (UF). UF and maleated starch (MS) were used as compatibilizing agents. The blending procedures included: (1) thermoextruding starch and zein as premixed powder materials (TP [Mix]) and (2) coextruding the biopolymers previously thermoplasticized with suitable plasticizers. As observed by the tensile tests, scanning electronic microscopy, and dynamic mechanical analysis, segregation of phases occurred at different extents in all the starch-zein blends. Materials made with MS through the TP [Mix] procedure presented the most severe phases segregation, while the materials made with UF showed higher compatibility between starch and zein. Fourier Transform Infrared Spectroscopy (FTIR) suggests that increased zein content leads to a lower molecular order, which was ascribed to diminished molecular entanglement. Thermogravimetric analysis and FTIR analysis showed that the chemical interaction between starch and zein occurred more extensively in slabs made with UF than those made with MS. In addition, foamability was evaluated for the selected materials using supercritical CO 2 . Neat thermoplasticized starch plasticized with UF and themoplasticized zein with polyethylene-glycol 400 showed good suitability to be foamed, producing foams with porosities above 85 %. Starch plasticized with SG and starch-zein blends yielded compact structures with low porosity values after foaming. Keywords Starch Á Zein Á Compatibilization Á Thermoplastic extrusion Á Foaming Abbreviations UF Urea and formamide mixture at 2:1 (wt:wt) ratio SG Sorbitol and glycerol mixture at 1.4:1 (wt:wt) ratio MS Maleated starch MSG Mixture of native/maleated starch (50:50) and SG as plasticizer TPS UF Native starch thermoplasticized with UF TPS SG Native starch thermoplasticized with SG TPS MSG Thermoplasticized MSG TPZ Zein thermoplasticized with PEG400 Mix[TP] Mixing thermoplasticized biopolymers through thermoextrusion TP[Mix] Thermoplasticizing powder compositions of biopolymers and plasticizers

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A novel probiotic product was developed, which was formulated as an oblea (wafer-type dehydrated traditional Mexican dessert) using goat sweet whey fermented with Bifidobacterium infantis or Lactobacillus acidophilus. To obtain the probiotic oblea, the fermented whey was formulated with prebiotic carbohydrates (inulin and resistant starch) and gelatin, and the preparation was poured onto a polytetrafluoroethylene-coated nonstick baking pan, dried in a convection oven, and finally dehydrated at a low relative humidity and room temperature (23±2°C). The amounts of prebiotic carbohydrates and gelatin to be used in the formulation were determined by a factorial experimental design. An untrained sensory panel evaluated 3 quality characteristics (film formation, homogeneity, and smoothness) in the final product. Three different drying temperatures were tested, namely, 40, 55, and 70°C. Bacterial survival at each temperature was determined by viable plate-counting. The best formulation, based on the quality characteristics tested, consisted of 58.33% (vol/vol) of fermented whey, 8.33% (vol/vol) of 6% (wt/vol) resistant starch dispersion, 16.66% (vol/vol) of 15% (wt/vol) inulin solution, and 16.66% (vol/vol) of a 10% (wt/vol) gelatin solution. Drying at 55±2°C for 2.66±0.22 h allowed for concentrations of probiotic bacteria above 9 log(10) cfu/g, which is above the minimum concentration required in a probiotic product.

BackgroundFoams are high porosity and low density materials. In nature, they are a common architecture. Some of their relevant technological applications include heat and sound insulation, lightweight materials, and tissue engineering scaffolds. Foams derived from natural polymers are particularly attractive for tissue culture due to their biodegradability and bio-compatibility. Here, the foaming potential of an extensive list of materials was assayed, including slabs elaborated from whole flour, the starch component only, or the protein fraction only of maize seeds.Methodology/Principal FindingsWe used supercritical CO2 to produce foams from thermoplasticized maize derived materials. Polyethylene-glycol, sorbitol/glycerol, or urea/formamide were used as plasticizers. We report expansion ratios, porosities, average pore sizes, pore morphologies, and pore size distributions for these materials. High porosity foams were obtained from zein thermoplasticized with polyethylene glycol, and from starch thermoplasticized with urea/formamide. Zein foams had a higher porosity than starch foams (88% and 85%, respectively) and a narrower and more evenly distributed pore size. Starch foams exhibited a wider span of pore sizes and a larger average pore size than zein (208.84 vs. 55.43 μm2, respectively). Proof-of-concept cell culture experiments confirmed that mouse fibroblasts (NIH 3T3) and two different prostate cancer cell lines (22RV1, DU145) attached to and proliferated on zein foams.Conclusions/SignificanceWe conducted screening and proof-of-concept experiments on the fabrication of foams from cereal-based bioplastics. We propose that a key indicator of foamability is the strain at break of the materials to be foamed (as calculated from stress vs. strain rate curves). Zein foams exhibit attractive properties (average pore size, pore size distribution, and porosity) for cell culture applications; we were able to establish and sustain mammalian cell cultures on zein foams for extended time periods.