Production of Cationic Starch-Based Flocculants and Their Application in Thickening and Dewatering of the Municipal Sewage Sludge

Polymer flocculants are used to promote solid–liquid separation processes in wastewater treatment technologies, and bio-based flocculants possess many advantages over conventional synthetic polymers. Potato starch microgranules were chemically modified and mechanically sheared to produce modified starch flocculants. The effectiveness of produced cationic starch (CS) and cross-linked cationic starch (CCS) flocculants in the thickening and dewatering of surplus activated sewage sludge was evaluated and compared with that of synthetic cationic flocculants (SCFs) The flocculation efficiency of SCF, CS, and CCS in sludge thickening was determined by measuring the filtration rate of treated surplus activated sludge. Comparing the optimal dose of SCFs and CCS flocculants needed for thickening, the CCS dose was more than 10 times higher, but a wide flocculation window was determined. The impact of used flocculants on the dewatering performance of surplus activated sludge at optimal dose conditions was investigated by measuring capillary suction time. The filtration efficiencies (dewaterability) of surplus activated sludge using SCF, CS, and CCS were 69, 67, and 72%, respectively. The study results imply that mechanically processed cross-linked cationic starch has a great potential to be used as an alternative green flocculant in surplus activated sludge thickening and dewatering operations in municipal sewage sludge treatment processes

Development of antioxidant food packaging materials containing eugenol for extending display life of fresh beef

In this study, clove essential oil (CL) or eugenol (EU) containing cellulose acetate (CA) or acrylic component/hydrophobically modified starch (AC/S) coatings on corona treated oriented polypropylene film (OPP) were designed and investigated for their possible applications as antioxidant packaging materials for fresh meat. The antioxidant properties of the coatings were investigated by Vapour Phase-DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. The CA coatings containing CL or EU showed 43-92% and 43-94% inhibition against DPPH free radicals through the vapour phase, respectively, whereas AC/S/CL and AC/S/EU coatings resulted in DPPH inhibition of 21-65% and 25-84%, respectively. AC/S/EU and CA/EU coatings on OPP containing from 0.32 ± 0.03 to 6.40 ± 0.14 g/m2 of EU were used to prepare packaging for fresh beef (Longissimus thoracis). After 14 days, the lipid oxidation in beef steaks kept in control and antioxidant packages was 3.33 and 1.00-1.22 mg of malondialdehyde per kilogram of meat, respectively. Moreover, red colour of beef in antioxidant packages was retained

Active packaging applications for food

The traditional role of food packaging is continuing to evolve in response to changing market needs. Current drivers such as consumer’s demand for safer, “healthier,” and higher-quality foods, ideally with a long shelf-life; the demand for convenient and transparent packaging, and the preference for more sustainable packaging materials, have led to the development of new packaging technologies, such as active packaging (AP). As defined in the European regulation (EC) No 450/2009, AP systems are designed to “deliberately incorporate components that would release or absorb substances into or from the packaged food or the environment surrounding the food.” Active packaging materials are thereby "intended to extend the shelf-life or to maintain or improve the condition of packaged food.” Although extensive research on AP technologies is being undertaken, many of these technologies have not yet been implemented successfully in commercial food packaging systems. Broad communication of their benefits in food product applications will facilitate the successful development and market introduction. In this review, an overview of AP technologies, such as antimicrobial, antioxidant or carbon dioxide-releasing systems, and systems absorbing oxygen, moisture or ethylene, is provided, and, in particular, scientific publications illustrating the benefits of such technologies for specific food products are reviewed. Furthermore, the challenges in applying such AP technologies to food systems and the anticipated direction of future developments are discussed. This review will provide food and packaging scientists with a thorough understanding of the benefits of AP technologies when applied to specific foods and hence can assist in accelerating commercial adoption

Bioplastics for Food Packaging: Environmental Impact, Trends and Regulatory Aspects

The demand to develop and produce eco-friendly alternatives for food packaging is increasing. The huge negative impact that the disposal of so-called “single-use plastics” has on the environment is propelling the market to search for new solutions, and requires initiatives to drive faster responses from the scientific community, the industry, and governmental bodies for the adoption and implementation of new materials. Bioplastics are an alternative group of materials that are partly or entirely produced from renewable sources. Some bioplastics are biodegradable or even compostable under the right conditions. This review presents the different properties of these materials, mechanisms of biodegradation, and their environmental impact, but also presents a holistic overview of the most important bioplastics available in the market and their potential application for food packaging, consumer perception of the bioplastics, regulatory aspects, and future challenges

The polymer physics and chemistry of microbial cell attachment and adhesion

The attachment of microbial cells to solid substrata is a primary ecological strategy for the survival of species and the development of specific activity and function within communities. An hypothesis arising from a biological sciences perspective may be stated as follows: The attachment of microbes to interfaces is controlled by the macromolecular structure of the cell wall and the functional genes that are induced for its biological synthesis. Following logically from this is the view that diverse attached cell behaviour is mediated by the physical and chemical interactions of these macromolecules in the interfacial region and with other cells. This aspect can be reduced to its simplest form by treating physico-chemical interactions as colloidal forces acting between an isolated cell and a solid or pseudo solid substratum. These forces can be analysed by established methods rooted in DLVO (Derjaguin, Landau, Verwey and Overbeek) theory. Such a methodology provides little insight into what governs changes in the behaviour of the cell wall attached to surfaces, or indeed other cells. Nor does it shed any light on the expulsion of macromolecules that modify the interface such as formation of slime layers. These physical and chemical problems must be treated at the more fundamental level of the structure and behaviour of the individual components of the cell wall, for example biosurfactants and extracellular polysaccharides. This allows us to restate the above hypothesis in physical sciences terms: Cell attachment and related cell growth behaviour is mediated by macromolecular physics and chemistry in the interfacial environment. Ecological success depends on the genetic potential to favourably influence the interface through adaptation of the macromolecular structure. We present research that merges these two perspectives. This is achieved by quantifying attached cell growth for genetically diverse model organisms, building chemical models that capture the variations in interfacial structure and quantifying the resulting physical interactions. Experimental observations combine aqueous chemistry techniques with surface spectroscopy in order to elucidate the cell wall structure. Atomic force microscopy methods quantify the physical interactions between the solid substrata and key components of the cell wall such as macromolecular biosurfactants. Our current approach focuses on considering individually mycolic acids or longer chain polymers harvested from cells, as well as characterised whole cells. This approach allows us to use a multifactorial approach to address the relative impact of the individual components of the cell wall in contact with model surfaces. We then combine these components to increase complexity step-wise, while comparing with the behaviour of entire cells. Eventually, such an approach should allow us to estimate and understand the primary factors governing microbial cell adhesion. Although the work addresses the cell–mineral interface at a fundamental level, the research is driven by a range of technology needs. The initial rationale was improved prediction of contaminant degradation in natural environments (soils, sediments, aquifers) for environmental cleanup. However, this area of research addresses a wide range of biotechnology areas including improved understanding of pathogen survival (e.g., in surgical environments), better process intensification in biomanufacturing (biofilm technologies) and new product development