Optimizing quality losses and shelf-life in bakery products by edible coatings

Edible packaging is of increasing interest as a technological strategy for preserving quality, improving shelf-life as well as reducing the residual waste associated with food packaging. Alternative packaging systems with coatings and films that are viable have already been proven useful in fresh produce, fresh cuts; meat and milk products. However, in the past decade interest has been renewed in edible packaging application for bakery products to restrict moisture migration, texture changes, mould growth, incorporate functional compounds and reduce overall packaging impact. The objective of this thesis was to develop edible coatings to mitigate quality losses in bakery products. The coating and product as dynamic systems with different physico-mechanical characteristics were assessed individually by, (i) development and characterization of edible coating matrices for bakery application; (ii) evaluation of the drying of edible coating on bread to optimize temperature and time of drying; (iii) effect of coating during storage as influenced by type of coating and stage of application. Based on the obtained results, characterization of rheological, mechanical and thermal characteristics of edible coatings and films were found particularly useful to select suitable coating matrices. The use of rapid methods like near infrared spectroscopy enabled the monitoring and modelling of optimal temperature/time combinations to dry coatings. Also, a numerical model to understand the heat and mass transfer dynamics for the coated bread was designed. Furthermore, the study on storage indicated that the use of edible coatings can have a retaining effect on the moisture and textural quality of bread. The results evidenced in this doctoral project can contribute to the understanding of the role of edible coatings for bread. They could be further designed as potential alternatives to reduce the level of barriers used for packaging, for a more sustainable and eco-friendly production chain

Stinging Nettles as Potential Food Additive: Effect of Drying Processes on Quality Characteristics of Leaf Powders

Abstract: Stinging nettle (Urtica dioica L.) is a ubiquitous, multi-utility, and under-utilized crop with potential health benefits owing to its nutritional and bioactive components. The objective of the work is to produce powders by drying wild stinging nettle leaves as a storable, low-cost functional additive to be used in bakery and ready-to-cook products. Convective drying (CD) and freeze-drying (FD) were applied on unblanched (U) or blanched (B) leaves, which were then milled to nettle powders (NPs). The obtained NPs were evaluated for selected physicochemical (moisture, color), techno- functional (flow indices, hygroscopicity), and phytochemical (pigments, phenols) characteristics as well as mineral contents. Blanching improved mass transfer and reduced the oxidative degradation of pigments during drying, but it caused a loss of total phenols content, antioxidant activity, and potassium content. As for the drying method, CD resulted in better flow properties (i.e., Carr Index and Hausner Ratio), while FD retained better the color, pigments, magnesium content, phenolic, and antioxidant parameters. Overall, the evaluated processing methods resulted in different technological properties that can allow for better evaluation of NPs as a food additive or ingredient. Among the NPs, blanched and freeze-dried powders despite showing inferior technological properties can be recommended as more suitable ingredients targeted f or food enrichment owing to better retention of bio-active components

A Review on High-Power Ultrasound-Assisted Extraction of Olive Oils: Effect on Oil Yield, Quality, Chemical Composition and Consumer Perception

The objective of this review is to illustrate the state of the art in high-power ultrasound (HPU) application for olive oil extraction with the most recent studies about the effects of HPU treatment on oil yield, quality, chemical composition, as well as on the consumer’s perception. All the examined works reported an increase in oil yield and extractability index through the use of HPU, which was ascribed to reduced paste viscosity and cavitation-driven cell disruption. Olive oil legal quality was generally not affected; on the other hand, results regarding oil chemical composition were conflicting with some studies reporting an increase of phenols, tocopherols, and volatile compounds, while others underlined no significant effects to even slight reductions after HPU treatment. Regarding the acceptability of oils extracted through HPU processing, consumer perception is not negatively affected, as long as the marketer effectively delivers information about the positive effects of ultrasound on oil quality and sensory aspect. However, only a few consumers were willing to pay more, and hence the cost of the innovative extraction must be carefully evaluated. Since most of the studies confirm the substantial potential of HPU to reduce processing times, improve process sustainability and produce oils with desired nutritional and sensory quality, this review points out the need for industrial scale-up of such innovative technology

PHYSICAL PROPERTIES OF PECTIN-ALGINATE-WHEY PROTEIN EDIBLE FILMS

Edible films are thin layer(s) of bio-based material formed as a part of food to extend their shelf-life. Whey Protein films are proposed to have good mechanical properties and ability to form transparent films. This study was carried out to understand the effects of combining whey protein, pectin and alginate on some physical and mechanical properties of film

Characterization of Composite Edible Films Based on Pectin/Alginate/Whey Protein Concentrate

Edible films and coatings gained renewed interest in the food packaging sector with polysaccharide and protein blending being explored as a promising strategy to improve properties of edible films. The present work studies composite edible films in different proportions of pectin (P), alginate (A) and whey Protein concentrate (WP) formulated with a simplex centroid mixture design and evaluated for physico-chemical characteristics to understand the effects of individual components on the final film performance. The studied matrices exhibited good film forming capacity, except for whey protein at a certain concentration, with thickness, elastic and optical properties correlated to the initial solution viscosity. A whey protein component in general lowered the viscosity of the initial solutions compared to that of alginate or pectin solutions. Subsequently, a whey protein component lowered the mechanical strength, as well as the affinity for water, as evidenced from an increasing contact angle. The effect of pectin was reflected in the yellowness index, whereas alginate and whey protein affected the opacity of film. Whey protein favored higher opacity, lower gas barrier values and dense structures, resulting from the polysaccharide-protein aggregates. All films displayed however good thermal stability, with degradation onset temperatures higher than 170 °C