Nowadays, consumers demand high quality food products with an extended shelf-life without chemical additives. Edible coatings (EC) containing natural compounds are a promising preservation technology for raw seafood without compromising fresh-like appeal and nutritional content. The aim of this work was to evaluate the effect of Thunnus obesus skin gelatin-based EC containing Codium spp. or Fucus vesiculosus extracts on raw tuna preservation. Three gelatin-based EC (gelatin (5 %) + glycerol (25 %); gelatin (5 %) + Codium spp. (1 %) + glycerol (25 %); gelatin (5 %) + Fucus vesiculosus (1 %) + glycerol (25 %)) were applied directly on the surface of tuna fillets. Functional properties of gelatin and gelatin-based EC containing seaweed extracts were also studied. The gelatin was extracted by an acid-swelling process in the presence/absence of pepsin, followed by subsequent heating/refrigeration, after a pre-treatment with NaOH. The type of acid, temperature and concentration of NaOH greatly influence the process yield. The higher extraction yield was achieved using acetic acid in the presence of pepsin by subsequent refrigeration, especially when skins were previously treated with NaOH (0.2 M). Tuna quality was assessed over 12 days of storage at 4 ± 1 °C in terms of chemical and microbial indices. Results showed that tuna skin gelatin-based EC avoids tuna deterioration. Microbial growth, assessed by total viable counts, and total volatile basic nitrogen were maintained below the maximum limits recommended, contrarily to the control. Additionally, the use of EC increased the stability of red colour during storage.

Wheat and cassava composite breads are generally associated with volume and textural defects in contrast with the traditional wheat based variants. Efforts to mitigate this challenge through use of synthetic additives have been unsuccessful owing to safety concerns. The objective of this study was to explore Grewia venusta mucilage as a potential natural additive in wheat-cassava composite bread production. Sweet cassava flour was used to replace wheat flour at 100: 0 (control), 90:10, 80:20 and 70:30% ratios in bread making. Aqueous extract of G. venusta stem bark was oven dried (50±3 °C), milled and added at 0, 1.0 and 2.0% (w/w) to the flour mixtures. These, along with other conventional inputs were mixed, and used to produce bread. Proximate compositions, physical and sensory properties of the bread loaves were evaluated. Cassava flour inclusion resulted in significant (P≤0.05) decrease in the protein content of the control from 18.1% to 12.1% (90:10%), 11.5% (80:20%) and 9.9% (70:30%). Addition of mucilage marginally increased the protein and dietary fibre contents of the loaves. Loaves containing 1-2% mucilage were more regular in shape with smoother crust than those without mucilage. Cassava flour addition at 10%, 20% and 30% decreased loaf height from 6.0 cm to 5.8 cm, 5.7 cm and 5.5 cm, as well as loaf volume from 815.5 cm3 to 783.1 cm3 , 776.8 cm3 and 744.5 cm3 , respectively. Mucilage inclusion resulted in increased heights and volumes of the loaves and reduced weights of loaf fragments upon slicing. The mucilage significantly improved the texture of the bread loaves.