Physical and Chemical Properties of Vegetable Films Based on Pumpkin Purée and Biopolymers of Plant and Animal Origin.

Highly methylated apple pectin (HMAP) and pork gelatin (PGEL) have been proposed as gelling agents for pumpkin purée-based films. Therefore, this research aimed to develop and evaluate the physiochemical properties of composite vegetable films. Granulometric analysis of film-forming solutions showed a bimodal particle size distribution, with two peaks near 25 µm and close to 100 µm in the volume distribution. The diameter D4.3, which is very sensitive to the presence of large particles, was only about 80 µm. Taking into account the possibility of creating a polymer matrix from pumpkin purée, its chemical characteristic was determined. The content of water-soluble pectin was about 0.2 g/100 g fresh mass, starch at the level of 5.5 g/100 g fresh mass, and protein at the level of about 1.4 g/100 g fresh mass. Glucose, fructose, and sucrose, the content of which ranged from about 1 to 1.4 g/100 g fresh mass, were responsible for the plasticizing effect of the purée. All of the tested composite films, based on selected hydrocolloids with the addition of pumpkin purée, were characterized by good mechanical strength, and the obtained parameters ranged from about 7 to over 10 MPa. Differential scanning calorimetry (DSC) analysis determined that the gelatin melting point ranged from over 57 to about 67 °C, depending on the hydrocolloid concentration. The modulated differential scanning calorimetry (MDSC) analysis results exhibited remarkably low glass transition temperature (Tg) values, ranging from -34.6 to -46.5 °C. These materials are not in a glassy state at room temperature (~25 °C). It was shown that the character of the pure components affected the phenomenon of water diffusion in the tested films, depending on the humidity of the surrounding environment. Gelatin-based films were more sensitive to water vapor than pectin ones, resulting in higher water uptake over time. The nature of the changes in water content as a function of its activity indicates that composite gelatin films, with the addition of pumpkin purée, are characterized by a greater ability to adsorb moisture from the surrounding environment compared to pectin films. In addition, it was observed that the nature of the changes in water vapor adsorption in the case of protein films is different in the first hours of adsorption than in the case of pectin films, and changes significantly after 10 h of the film staying in an environment with relative humidity RH = 75.3%. The obtained results showed that pumpkin purée is a valuable plant material, which can form continuous films with the addition of gelling agents; however, practical application as edible sheets or wraps for food products needs to be preceded with additional research on its stability and interactions between films and food ingredients.

Influence of Tea Brewing Parameters on the Antioxidant Potential of Infusions and Extracts Depending on the Degree of Processing of the Leaves of Camellia sinensis.

The polyphenol content of tea depends on the growing region, harvest date, the production process used, and the brewing parameters. In this study, research was undertaken that included an analysis of the influence of the brewing process parameters on the content of total polyphenols (Folin-Ciocalteu), epigallocatechin gallate (HPLC), and antioxidant activity (against DPPH radicals) of fresh tea shrub leaves grown from Taiwan and of teas obtained from them (oolong, green in bags, and green loose from the spring and autumn harvest). The antioxidant potential was determined in the methanol and aqueous extracts, as well as in infusions that were obtained by using water at 65 or 100 °C and infusing the tea for 5 or 10 min. The highest content of total polyphenols and epigallocatechin gallate was found in green tea extracts from the spring harvest. However, in the case of infusions, the highest content of these compounds was found in green tea in bags. Steaming at 100 °C for 10 min, turned out to be the most favourable condition for the extraction. Oolong tea, brewed at 100 °C for 5 min was characterised by the highest antioxidant activity against stable DPPH radicals.

Development and Characterization of Novel Composite Films Based on Soy Protein Isolate and Oilseed Flours.

The possibility of using oilseed flours as a waste source for film-forming materials with a combination of soy protein isolate in preparation of edible films was evaluated. Physical, mechanical and barrier properties were determined as a function of the oilseed type: hemp, evening primrose, flax, pumpkin, sesame and sunflower. It was observed that the addition of oilseed flours increased the refraction and thus the opacity of the obtained films from 1.27 to 9.57 A mm-1. Depending on the type of flours used, the edible films took on various colors. Lightness (L*) was lowest for the evening primrose film (L* = 34.91) and highest for the soy protein film (L* = 91.84). Parameter a* was lowest for the sunflower film (a* = -5.13) and highest for the flax film (a* = 13.62). Edible films made of pumpkin seed flour had the highest value of the b* color parameter (b* = 34.40), while films made of evening primrose flour had the lowest value (b* = 1.35). All analyzed films had relatively low mechanical resistance, with tensile strength from 0.60 to 3.09 MPa. Films made of flour containing the highest amount of protein, pumpkin and sesame, had the highest water vapor permeability, 2.41 and 2.70 × 10-9 g·m-1 s-1 Pa-1, respectively. All the edible films obtained had high water swelling values from 131.10 to 362.16%, and the microstructure of the films changed after adding the flour, from homogeneous and smooth to rough. All blended soy protein isolate-oilseed flour films showed lower thermal stability which was better observed at the first and second stages of thermogravimetric analysis when degradation occurred at lower temperatures. The oilseed flours blended with soy protein isolate show the possibility of using them in the development of biodegradable films which can find practical application in the food industry.

The Use of Antioxidant Potential of Chokeberry Juice in Creating Pro-Healthy Dried Apples by Hybrid (Convection-Microwave-Vacuum) Method.

The visible trend in the development of the snack market focuses on the use of innovative technologies such as low-temperature or hybrid processes that allow the preservation of native ingredients of raw plant materials. In addition, the high antioxidant potential of, for example, chokeberry fruit can be used to support technological processes and create new products. The aim of the study was to evaluate the possibility of using chokeberry juice concentrate as a component of an osmotic solution to enrich apple samples with natural bio-ingredients and obtain dried apples with increased content of ingredients with antioxidant properties; pro-healthy apple chips. The research material consisted of apples that underwent osmotic dehydration in solutions of sucrose or sucrose and chokeberry juice concentrate and then were dried by the freeze-drying or the hybrid method. The freeze-drying was more beneficial for maintaining the vitamin C content, while the use of the hybrid method resulted in the preservation of more polyphenolic compounds. The sensory evaluation indicated the need to modify the composition of the osmoactive solution. Due to the use of chokeberry juice concentrate, the content of vitamin C, polyphenols, and the antioxidant activity of dried apples was increased.