Sumeet Dhawan

Biodegradable Poly(butylene adipate‐co‐terephthalate) Films Incorporated with Nisin: Characterization and Effectiveness against Listeria innocua

Biodegradable poly(butylene adipate-co-terephthalate) (PBAT) films incorporated with nisin were prepared with concentrations of 0, 1000, 3000, and 5000 international units per cm(2) (IU/cm(2)). All the films with nisin inhibited Listeria innocua, and generated inhibition zones with diameters ranging from 14 to 17 mm. The water vapor permeability and oxygen permeability after the addition of nisin ranged from 3.05 to 3.61 x 10(11) g m m(-2) s(-1) Pa(-1) and from 4.80 x 10(7) to 11.26 x 10(7) mL.m.m(-2).d(-1).Pa(-1), respectively. The elongation at break (epsilon(b)) was not altered by the incorporation of nisin (P > 0.05). Significant effect was found for the elastic modulus (E) and the tensile strength (sigma(s)) (P < 0.05). The glass transition and melting temperatures with the presence of nisin ranged from -36.3 to -36.6 degrees C and from 122.5 to 124.2 degrees C, respectively. The thermal transition parameters such as the crystallization and melting enthalpies and crystallization temperature were influenced significantly (P < 0.05) by incorporation of nisin into films. The X-ray diffraction patterns exhibited decreasing levels of intensity (counts) as the concentration of nisin increased in a range of 2theta from 8 degrees to 35 degrees . Formation of holes and pores was observed from the environmental scanning electron microscopy images in the films containing nisin, suggesting interaction between PBAT and nisin.

Physicochemical Properties of Encapsulated Red Raspberry (Rubus idaeus) Powder: Influence of High-Pressure Homogenization

Encapsulated red raspberry (Rubus idaeus) powders with gum arabic were produced using a spray-drying method. The raspberry puree samples were treated with and without high-pressure homogenizers prior to spray drying. The physicochemical properties of spray-dried raspberry powders were analyzed. The median particle size (X 50) of raspberry powder produced with high-pressure homogenized puree (14.6 µm) was smaller than raspberry powder produced without high-pressure homogenization applied to puree (18.3 µm). Glass transition temperatures and water contents of encapsulated raspberry powders were not significantly different (p > 0.05) at equivalent water activities. High-pressure homogenization of puree resulted in greater apparent density and porosity for encapsulated raspberry powder. Greater particle size resulted in higher hygroscopicity and water solubility index (WSI) for encapsulated raspberry powder produced without high-pressure homogenization of puree. Anthocyanins concentration was greater in raspberry powder pretreated with high-pressure homogenization although powder exhibited lower brightness, redness, and yellowness.