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This paper is part of a series examining the impact of the main factors influencing lipid digestion and nutraceutical bioaccessibility in β-carotene-loaded oil-in-water emulsions using the harmonized INFOGEST simulated gastrointestinal model. Here, the impact of emulsifier type was examined since food emulsions and nutraceutical delivery systems are often stabilized by various types of emulsifier. The INFOGEST method was adopted to investigate the in vitro gastrointestinal fate of emulsions stabilized by five kinds of food-grade emulsifier representing different classes: synthetic surfactants (Tween 20); natural surfactants (quillaja saponin); proteins (caseinate); polysaccharides (gum arabic); and phospholipids (soy lysolecithin). Microfluidization produced emulsions with small droplet sizes for all emulsifiers, except soy lysolecithin. Within the gastrointestinal model, the caseinate-coated oil droplets had the worst gastric stability, with severe droplet flocculation and coalescence occurring in the stomach. The fraction of the lipid phase that had been digested by the end of the gastrointestinal model was considerably lower for the emulsions stabilized by soy lysolecithin (93%) or caseinate (93%), than those stabilized by gum arabic (99%), quillaja saponin (111%) or Tween 20 (117%). This effect was attributed to lower surface area of lipids available for lipase to attach to for the lysolecithin and caseinate emulsions. The overall bioaccessibility of the β-carotene increased in this order: lysolecithin (25%) < gum arabic (51%) < caseinate (55%) < quillaja saponin (56%) < Tween 20 (62%). The impact of emulsifier type on carotenoid bioaccessibility was ascribed to various factors: (i) some emulsifiers inhibited lipid digestion and so a fraction of the β-carotene remained inside the undigested droplets and the mixed micelle phase had less solubilization capacity, i.e., lysolecithin, and caseinate; (ii) some emulsifiers protected β-carotene from chemical degradation, i.e., lysolecithin and caseinate; and (iii) some emulsifiers promoted sedimentation of the β-carotene-loaded micelles, i.e., lysolecithin. These results suggest that food emulsion behavior in the human gut may be influenced by the nature of the emulsifier employed, which is important knowledge when creating functional food and beverage products., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Food, nutrition, and pharmaceutical scientists are trying to elucidate the major factors impacting the bioavailability of macronutrients (e.g., lipids) and micronutrients (e.g., vitamins) so as to improve their efficacy. Currently, there is still a limited understanding of how food matrix effects impact digestion and bioaccessibility determined under the INFOGEST model, which is currently the most widely used standardized in vitro gastrointestinal model. Therefore, we examined the impact of corn oil concentration on lipid digestion and β-carotene bioaccessibility using model food emulsions. For all oil concentrations tested (2.5 to 20%), complete lipid digestion was achieved using fed-state gastrointestinal conditions, which could only be seen if a back-titration was performed. The particle size and negative surface potential on the mixed micelles formed at the end of the small intestine phase both increased with increasing oil concentration, which was attributed to the generation of more free fatty acids. The β-carotene bioaccessibility increased when the oil concentration was raised from 2.5 to 10% due to the increased solubilization capacity of the mixed micelles, but then it decreased when the oil concentration was raised further to 20% due to precipitation and sedimentation of some of the β-carotene. The maximum β-carotene bioaccessibility (93.2%) was measured at 10% oil. These results indicate that the oil concentration of emulsions influences β-carotene bioaccessibility by altering digestion, solubilization, and precipitation processes. This knowledge is important when designing more effective functional or medical food products.

Summary: This study was designed to evaluate the effect of different cooking methods on the protein digestion characteristics of channel fish (Ietalurus punetaus). The channel fish muscles were subjected to different cooking methods, namely boiling, steaming and roasting and were subjected to in vitro gastrointestinal digestion simulation using raw fish as a control. All the cooking methods increased the protein digestibility (1.60–8.28%) and decreased the protein particle size at the end of the gastrointestinal digestion. The highest protein digestibility (66.78%) and the smallest protein particle size values (600.7 nm) were observed for the steamed group. Samples which were steam cooked showed lowest β‐sheet content (9.63 ± 0.81%) and were accompanied with moderate protein oxidation. As the core temperature increased from 40°C to 90°C, protein oxidation increased significantly (P < 0.05) with the increase of carbonyl groups and Schiff bases and decrease of sulfhydryl groups in all cooked groups. Based on the results, steaming was recommended as the best methods of cooking channel fish for improved protein digestibility. [ABSTRACT FROM AUTHOR]

• Protein/polysaccharide beads were fabricated from plant and animal proteins. • All beads were digested slowly in the stomach but rapidly in the small intestine. • Raman spectroscopy was used to analyze beads during gastrointestinal digestion. • Similar digestion behaviors were observed for whey, soy and pea protein beads. • Animal proteins can be replaced by plant ones in hydrogel delivery systems. In this study, we encapsulated both animal-derived (whey) and plant-derived (soy and pea) proteins within polysaccharide/protein beads and measured the digestion of these beads under simulated gastrointestinal tract (GIT) conditions. Bead dimensions were measured using a digital caliper and found to increase as the shear thinning behavior of the protein/polysaccharide solutions used to form them increased. The hydrolysis of the plant and animal proteins trapped inside the protein/polysaccharide beads was studied using the pH-stat automatic titration method under simulated static GIT conditions. The encapsulated proteins were relatively resistant to digestion under gastric conditions, with only about 10 to 13% of the protein being digested by the end of the stomach phase. Conversely, they were almost fully digested under small intestinal conditions, with around 87 to 97% of the protein being hydrolyzed by the end. Indeed, by the completion of the small intestine phase, only "ghost" beads remained that contained cross-linked polysaccharides. The soy and pea proteins were digested slightly faster than the whey proteins in the stomach phase (p < 0.05), whereas the pea proteins were digested slightly faster than the soy and whey proteins under intestinal conditions (p < 0.05). Raman spectroscopy and scanning electron microscopy showed that there were changes in the composition and structure of the beads throughout the simulated GIT. Our results indicate that the gastrointestinal behavior of proteins can be modulated by encapsulating them in polysaccharide beads, which may be useful for the design of certain types of functional foods. Even so, the beads formed from the plant-based and animal-based proteins behaved fairly similarly, suggesting that animal proteins could be replaced by plant-based ones for this purpose. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of CIP pretreatment on the AD of RS was investigated. • CIP pretreatment altered the microstructure of RS. • The microbiological community was improved by CIP pretreatment. • Feasibility analysis of CIP pretreatment was carried out. In this study, rice straw was pretreated using by cold isostatic pressure to disrupt its microstructure and improve the performance of anaerobic digestion, and the optimal process parameters were optimized using the response surface methodology. The results showed that cold isostatic pressure pretreatment under optimal conditions (pressure of 400 MPa and holding time of 9 min) was effective in disrupting the structure of rice straw and improving its biodegradability. The cumulative methane production of the cold isostatic pressure pretreatment group increased by 76% compared to the untreated group. In addition, microbial community analysis showed that the relative abundance of Firmicutes , Halobacterota , DMER64 and Methanosaeta was higher in groups pretreated with cold isostatic pressure than in untreated groups. This study demonstrated the potential of pretreatment of rice straw with cold isostatic pressure to increase methane production during anaerobic digestion. [ABSTRACT FROM AUTHOR]