Chelo González-Martínez

Recent Advances in Edible Coatings for Fresh and Minimally Processed Fruits

The development of new edible coatings with improved functionality and performance for fresh and minimally processed fruits is one of the challenges of the post harvest industry. In the past few years, research efforts have focused on the design of new eco-friendly coatings based on biodegradable polymers, which not only reduce the requirements of packaging but also lead to the conversion of by-products of the food industry into value added film-forming components. This work reviews the different coating formulations and applications available at present, as well as the main results of the most recent investigations carried out on the topic. Traditionally, edible coatings have been used as a barrier to minimize water loss and delay the natural senescence of coated fruits through selective permeability to gases. However, the new generation of edible coatings is being especially designed to allow the incorporation and/or controlled release of antioxidants, vitamins, nutraceuticals, and natural antimicrobial agents by means of the application of promising technologies such as nanoencapsulation and the layer-by-layer assembly.

Influence of substituting milk powder for whey powder on yoghurt quality

Abstract Milk whey is an important source of lactose, calcium, milk proteins and soluble vitamins, which make this product be considered as functional food and a source of valuable nutrients. In this work, whey powder was used to substitute partially the milk powder in yoghurt fortification. Five different formulations were obtained and analysed for acidity, pH, gel consistency and microstructure and flow behaviour, colour (CIE L*, a*, b*) and syneresis index, after 1, 15 and 28 storage days at 5°C. Sensory properties were also evaluated after 15 storage days. Results show that the use of whey powder implies a slower acidification rate in yoghurts which becomes a little yellowish. They also show a better flow properties and greater syneresis than those obtained for products prepared with skim mil powder. Yoghurt samples with highest WP percentage (3.64–5.20%) were preferred by the sensorial panel.

Antioxidant edible films based on chitosan and starch containing polyphenols from thyme extracts

The aim of this study was to analyse the antioxidant activity of different polymeric matrices based on chitosan and starch, incorporating a thyme extract (TE) rich in polyphenols. TE provided the films with remarkable antioxidant activity. When mixed with chitosan, the polyphenols interacted with the polymer chains, acting as crosslinkers and enhancing the tensile behaviour of films. The opposite effect was observed when incorporated into the starch matrix. All the films became darker, more reddish and less transparent when TE was incorporated. These colour changes were more marked in starch matrices, which suggests that TE compounds were poorly encapsulated. The use of chitosan-based matrices carrying TE polyphenols is recommended as a means of obtaining antioxidant films, on the basis of their tensile response and greater antioxidant activity, which could be associated with the development of polyphenol-chitosan interactions, contributing to a better protection of the functionality of polyphenols during film formation and conditioning.

Recent patents on food applications of chitosan.

Chitosan is a natural polysaccharide that has become of great interest due to its multiple possible applications, which is a great challenge for both the scientific community and the food industry. Chitosan offers a wide range of food applications, including formation of biodegradable films and coatings, immobilization of enzymes, as an antimicrobial agent, and dietary supplement with hypocholesterolemic properties. The number of issued patents on the application of chitosan and its derivatives has been increasing steadily in the last decade. The present works reviews recent patents and important developments related to the use of chitosan in food industry.

Combination of Poly(lactic) Acid and Starch for Biodegradable Food Packaging

The massive use of synthetic plastics, in particular in the food packaging area, has a great environmental impact, and alternative more ecologic materials are being required. Poly(lactic) acid (PLA) and starch have been extensively studied as potential replacements for non-degradable petrochemical polymers on the basis of their availability, adequate food contact properties and competitive cost. Nevertheless, both polymers exhibit some drawbacks for packaging uses and need to be adapted to the food packaging requirements. Starch, in particular, is very water sensitive and its film properties are heavily dependent on the moisture content, exhibiting relatively low mechanical resistance. PLA films are very brittle and offer low resistance to oxygen permeation. Their combination as blend or multilayer films could provide properties that are more adequate for packaging purposes on the basis of their complementary characteristics. The main characteristics of PLA and starch in terms of not only the barrier and mechanical properties of their films but also of their combinations, by using blending or multilayer strategies, have been analyzed, identifying components or processes that favor the polymer compatibility and the good performance of the combined materials. The properties of some blends/combinations have been discussed in comparison with those of pure polymer films.

Release of polyphenols from starch-chitosan based films containing thyme extract

The release kinetics of thyme extract polyphenols (TE) from chitosan (CH), pea starch (S) and CH:S blend films in different solvents was evaluated, as well as their antioxidant activity in each release media. Pure starch films showed the fastest delivery rate and the highest delivery ratio of polyphenols, although the corresponding release media exhibited the lowest antioxidant capacity. TE provided CH based films with remarkable antioxidant activity, despite the lower polyphenol release obtained in all solvents, due to the strong polyphenols-chitosan interactions. The maximum amount of polyphenols delivered was found in the acetic acid solution, due to the high solubility of CH. The incorporation of tannic acid (TA) into CH films promoted cross-linking effect, which delays the TE release rate in water and ethanol aqueous solutions, except for CH:S:TA films. Thus, the polarity of the solvents and the polyphenols-matrix interactions markedly affected the polyphenol release and the antioxidant activity of the films.

Development of a non-dairy probiotic fermented product based on almond milk and inulin

A new fermented almond “milk” that combined the properties of both almonds and probiotics was considered to cover the current versatile health-promoting foods’ demand. Almond milk fermentation with probiotic Lactobacillus reuteri and Streptococcus thermophilus was studied by using a Central Composite design with response surface methodology, and different factors (glucose, fructose, inulin and starters) were optimised to assure high probiotic survivals in the final product. The optimal formulation was physicochemically characterised throughout cold storage (28 days) and both probiotic survivals to in vitro digestion and proteolysis were quantified. Results showed that a high probiotic population (>107 cfu/mL) was obtained in the previously optimised almond milk throughout storage time, which correspond to the addition of 0.75 g of glucose/100 mL, 0.75 g of fructose/100 mL, 2 g/100 mL inulin and 6 mL/100 mL inoculum. Glucose was used as the main nutrient and the production of mannitol by L. reuteri was detected. The fermentation process increased the viscosity values, forming a weak gel structure, whose physical properties hardly changed. Probiotic bacteria notably survived (51%) to the in vitro digestion, surely related to the inulin presence, which would add value to the developed product by enhancing the potential health benefits of its consumption.

Physical and Antimicrobial Properties of Starch-PVA Blend Films as Affected by the Incorporation of Natural Antimicrobial Agents

In this work, active films based on starch and PVA (S:PVA ratio of 2:1) were developed by incorporating neem (NO) and oregano essential oils (OEO). First, a screening of the antifungal effectiveness of different natural extracts (echinacea, horsetail extract, liquid smoke and neem seed oil) against two fungus (P. expansum and A. niger) was carried out. The effect of NO and OEO incorporation on the films’ physical and antimicrobial properties was analyzed. Only composite films containing OEO exhibited antibacterial and antifungal activity. Antibacterial activity occurred at low OEO concentration (6.7%), while antifungal effect required higher doses of OEO in the films. Incorporation of oils did not notably affect the water sorption capacity and water vapor barrier properties of S-PVA films, but reduced their transparency and gloss, especially at the highest concentrations. The mechanical response of the S-PVA films was also negatively affected by oil incorporation but this was only relevant at the highest oil ratio (22%). S-PVA films with 6.7% of OEO exhibited the best physical properties, without significant differences with respect to the S-PVA matrix, while exhibiting antibacterial activity. Thus, the use of OEO as a natural antimicrobial incorporated into starch-PVA films represents a good and novel alternative in food packaging applications.

Active Edible and Biodegradable Starch Films

Starch appears as a good alternative to petro-based plastics. This biopolymer exhibits a greater potential to obtain biodegradable films, thanks to its easy availability and low cost. Starch has been used to develop edible, biodegradable, active films using different strategies: blending with antimicrobial polymers, active nanoparticles, and other antioxidant or antimicrobial compounds, such as essential oils of phenolic extracts. The incorporation of these compounds to starch or starch blend films has an impact on their physical properties which can affect their functionality as a packaging material.

Horchata de Chufa: A Traditional Spanish Beverage with Exceptional Organoleptic, Nutritive, and Functional Attributes

In this chapter, the composition, nutritional value, and manufacture process of Horchata de chufa, a traditional Spanish beverage is explained. This healthy beverage is obtained from dried tiger nut tubers and its consumption is very seasonal, being mostly the summer months, thanks to its refreshing properties.