Protein gelation is important to obtain desirable sensory and textural structures in foods. Gelation phenomenon requires a driving force to unfold the native protein structure, followed by an aggregation retaining a certain degree of order in the matrix formed by association between protein strands. Protein gelation has been traditionally achieved by heating, but some physical and chemical processes form protein gels in an analogous way to heat-induction. A physical means, besides heat, is high pressure. Chemical means are acidification, enzymatic cross-linking, and use of salts and urea, causing modifications in protein-protein and protein-medium interactions. The characteristics of each gel are different and dependent upon factors like protein concentration, degree of denaturation caused by pH, temperature, ionic strength and=or pressure.

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Agroindustrial by-products derived from fruit processing are an important source of biocompounds that can be used as functional food ingredients. The objective of this work was to evaluate cactus pear and pineapple peel flours as an alternative carbon source during fermentation using bacteria with probiotic potential. The total fibre content of both flours was over 60%, with total soluble carbohydrate content around 20%, indicating a good carbon source for lactic acid bacteria. Kinetic parameters indicate that peel flours are a suitable carbon source because the lactic acid bacteria grow (mean growth rate constant, k, values close to glucose, 1.52 h) and acidify the culture media (maximum acidification rate, V max , approximately 1.60 pH 9 10 À3 min À1 ). There was no difference in prebiotic potential or prebiotic activity score for both the peel flours. Pediococcus pentosaceus performs better during fermentation. In this respect, cactus pear and pineapple peel flours can be used as functional ingredients due to their fermentable properties.Fruit peels as functional ingredients J. Diaz-Vela et al. Fruit peels as functional ingredients J. Diaz-Vela et al. Strain Carbon source pH final N (Log CFU mL À1 ) Pediococcus pentosaceus UAM22 Glucose (control) 4.39 AE 0.28 C,a 9.52 AE 0.25 A,a Cactus pear flour 5.81 AE 0.35 C,a 9.65 AE 0.25 A,a Pineapple flour 4.89 AE 0.42 C,a 9.56 AE 0.31 A,a Aerococcus viridans UAM21 Glucose (control) 6.12 AE 0.63 B,a 9.22 AE 0.24 B,a Cactus pear flour 5.64 AE 0.85 B,a 8.73 AE 0.25 B,a Pineapple flour 7.88 AE 0.21 B,a 9.33 AE 0.13 B,a Lactobacillus rhamnosus GG Glucose (control) 5.82 AE 0.57 C,a 9.24 AE 0.27 B,a Cactus pear flour 4.63 AE 0.85 C,a 8.77 AE 0.15 B,a Pineapple flour 5.15 AE 0.56 C,a 9.38 AE 0.26 B,a Escherichia coli K12 Glucose (control) 5.91 AE 0.21 A,a 8.46 AE 0.11 C,a Cactus pear flour 6.29 AE 0.14 A,a 8.63 AE 0.24 C,a Pineapple flour 6.68 AE 0.42 A,a 8.21 AE 0.22 C,a A, B, C, D means with same letter in same column are not significantly different (P > 0.05) for strain type. a, b means with same letter in same column are not significantly different (P > 0.05) for carbon source. Pediococcus pentosaceus UAM22 Cactus pear flour 0.33 AE 0.03 A,a Pineapple flour 0.32 AE 0.01 A,a Aerococcus viridans UAM21 Cactus pear flour À0.03 AE 0.02 C,a Pineapple flour 0.09 AE 0.02 C,a Lactobacillus rhamnosus GG Cactus pear flour 0.19 AE 0.01 B,a Pineapple flour 0.21 AE 0.02 B,aA, B, C means with same letter in same column are not significantly different (P > 0.05) for strain type. a, b means with same letter in same column are not significantly different (P > 0.05) for carbon source.Fruit peels as functional ingredients J. Diaz-Vela et al.

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Saturated animal fat was replaced in pork pâté with pre-emulsified canola in a 3% sodium caseinate/0.5% xanthan gum solution in order to obtain a stable oily phase. Fat was replaced with different proportions of emulsified canola oil. The inclusion of emulsified oil in pâté enhanced cocking yield and moisture but increased fluids release. Nonetheless, total fat content remained practically constant, meaning no detrimental effect on caloric content. Replacing 50% of lard with emulsified oil did not affect color of the samples. Texture was improved since emulsified oil addition resulted in softer and more spreadable pâté. Samples with 50% of emulsified oil were more stable to lipid oxidation at 8 days of storage, with lower thiobarbituric acid-reactive substances and volatile compounds resulting from oxidation reactions. Emulsified canola can be employed to replace fat until 50% in pâté or liver sausage with good functional properties, improving texture and reducing lipids rancidity.