Digestion kinetics of lipids and proteins in plant-based shakes: Impact of processing conditions and resulting structural properties

Effect of Inulin and Psyllium Husk Powder on Gel Properties and In Vitro Digestion of Hypophthalmichthys molitrix and Argopecten irradians Blended Surimi

Dietary fiber is crucial in enhancing the nutritional and textural properties of surimi-based products. This study investigated blended surimi produced from silver carp and bay scallops, with the addition of different amounts (0%, 0.5%, 1%, 2%, and 3%) of inulin (INU) or psyllium husk powder (PHP) for their textural properties, protein conformation, and in vitro digestibility. The addition of INU negatively affected gel strength. However, incorporating 2.0% PHP into the blended gel improved gel strength and water-holding capacity by 8.01% and 0.79% compared to the control, respectively. Furthermore, PHP significantly increased the total sulfhydryl content and surface hydrophobicity of the blended gels (p < 0.05). Additionally, increases in endogenous fluorescence intensity accompanied by a blue shift were observed, indicating that the fluorophores (Trp and Tyr) were sequestered into a more non-polar environment due to conformational changes. The incorporation of PHP enhanced both the quality and digestibility of the blended surimi. This study provides a novel perspective for developing surimi-based food with improved quality, augmented digestion, and enhanced absorption.

Macronutrient digestion and polyphenol bioaccessibility in oat milk tea products: an in vitro gastrointestinal tract study

People are increasingly preparing milk tea using plant-based milks rather than cow's milk, e.g., vegans, those with lactose intolerance, and those with flavor preferences. However, adding plant-based milks to tea may impact the digestion, release, and bioaccessibility of nutrients and nutraceuticals in both the tea and milk. In this study, oat milk tea model systems (OMTMSs) containing different fat and tea polyphenol concentrations were used to explore the impact of tea on macronutrient digestion in oat milk, as well as the impact of oat milk matrix on the polyphenol bioaccessibility in the tea. An in vitro gastrointestinal model that mimics the mouth, stomach, and small intestine was used. Tea polyphenols (>0.25%) significantly reduced the glucose and free fatty acids released from oat milk after intestinal digestion. Tea polyphenols (>0.10%) also inhibited protein digestion in oat milk during gastric digestion but not during intestinal digestion. The bioaccessibility of the polyphenols in the tea depended on the fat content of oat milk, being higher for medium-fat (3.0%) and high-fat (5.8%) oat milk than low-fat (1.5%) oat milk. Liquid chromatography-tandem mass spectrometry (UPLC-ESI-MS/MS) analysis showed that lipids improved the tea polyphenol bioaccessibility by influencing the release of flavonoids and phenolic acids from the food matrices. These results provide important information about the impact of tea on the gastrointestinal fate of oat milk, and vice versa, which may be important for enhancing the healthiness of plant-based beverages.

Solubility, (micro)structure, and in vitro digestion of pea protein dispersions as affected by high pressure homogenization and environmental conditions

In this work, dispersions were prepared with commercial pea protein isolate (PPI) and subjected to different (i) high pressure homogenization (HPH) intensities (0 - 200 MPa) (room temperature, pH 7) or (ii) environmental conditions (60 °C, pH 7 or pH 12) to generate dispersions with distinct protein molecular and microstructural characteristics, impacting protein solubility. Besides, protein digestion was analyzed following the static INFOGEST in vitro digestion protocol. Generally, increasing pressure of the homogenization treatment was linked with decreasing particle sizes and enhanced protein digestion. More specifically, the dispersion that did not undergo HPH (0 MPa) as well as the dispersion treated at 60 °C, pH 7, had highly similar microstructures, consisting of large irregular particles (10 - 500 µm) with shell-like structures, and exhibited low solubility (around 15 % and 28 %, respectively), which resulted in limited proteolysis (35 % and 42 %, respectively). In contrast, the dispersion subjected to HPH at 100 MPa and the dispersion treated at 60 °C, pH 12 also had similar microstructures with small and homogeneous particles (<1 µm), and exhibited relatively good solubility (54 % and 31 %, respectively), which led to enhanced protein digestion levels (87 % and 74 %, respectively). This study highlights the potential of food processing on macronutrient (micro)structure and further gastrointestinal stability and functionality.

Evaluating the effect of thermo-reversible and thermo-irreversible curdlan gels on the gelling properties and in vitro digestibility of myofibrillar protein gels under low-salt condition

The purpose of the present study was to investigate the gelling properties and in vitro digestibility of myofibrillar protein (MP) gels under low-salt condition as mediated by different concentrations of thermo-reversible curdlan gels (TRC) or thermo-irreversible curdlan gels (TIRC). The results showed that the incorporation of TRC or TIRC obviously improved the gel strength and water holding capacity of MP gels (P < 0.05). Those properties were most improved by adding 0.3 % TRC or TIRC with gel strength of 0.18 N or 0.17 N and WHC of 54.85 % or 49.05 %. Meanwhile, both TRC and TIRC promoted the transformation of α-helix into β-sheet, as well as hydrophobic interactions and disulfide bonds, which are the main forces for the maintenance of the MP gels. The microstructure revealed that the formation of dense and uniform protein network structures can be promoted by the addition of TRC or TIRC. The different modes of interaction between TRC or TIRC and MP resulted in different microstructures of the MP gels. Furthermore, incorporation of TRC or TIRC significantly reduced in vitro protein digestibility, especially for the 0.3 % (w/w) form (P < 0.05). Meanwhile, MP gels had the lowest in vitro protein digestibility after the addition of TRC (66.67 %) compared to the form of TIRC (70.93 %). Therefore, our present study indicated that incorporation form of TRC or TIRC have distinct implications on regulating the gelling properties and in vitro digestibility of MP gels under low-salt condition.

Effect of fat concentration on protein digestibility of Chinese sausage

Chinese sausage is a popular traditional Chinese meat product, but its high-fat content makes consumers hesitant. The purpose of this study is to compare the nutritional differences of Chinese sausages with different fermentation times (0, 10, 20, 30 d) and fat content (the initial content was 11.59% and 20.14%) during digestion. The comparison of digestion degree, protein structure, and peptide composition between different sausages were studied through in vitro simulated digestion. Chinese sausages with high-fat content had higher α-helix, β-turn, and random coil, making them easier to digest. The fermentation process made this phenomenon more pronounced. The high-fat sausage fermented for 10 d showed the highest release of primary amino acids (about 9.5%), which was about 3.5% higher than the low-fat sausage under the same conditions. The results of peptidomics confirmed the relevant conclusions. After gastric digestion, the types of peptides in the digestive fluid of high-fat sausages were generally more than those in low-fat sausages, while after intestinal digestion, the opposite results were observed. The type of peptide reached its peak after fermentation for 20 d. These findings are of obvious significance for selecting the appropriate fermentation time and fat content of Chinese sausages.

Pea protein extraction method impacts the protein (micro)structural organisation and in vitro digestion kinetics

There is increasing interest in including pulse proteins into food products due to their nutrient-rich and sustainable character. However, little is known regarding the consequences of different extraction approaches on the pulse protein structure and the subsequent protein (micro)structural organization and protein digestion kinetics. Therefore, three green pea protein extracts were created: (i) cooking followed by cotyledon cell isolation, (ii) alkaline extraction followed by isoelectric precipitation, or (iii) salt extraction, and compared to the original pea flour as well as to sodium caseinate. The results showed that encapsulated, denatured protein inside pea cotyledon cells presented the (s)lowest digestion, while accessible and more native protein (e.g., pea flour, pea protein salt extract) presented much faster and higher digestion. Moreover, the alkali extracted pea protein was denatured to some extent, significantly lowering in vitro digestion kinetics. In the second part, three different in vitro approaches were applied to digest the salt extracted pea protein. Semi-dynamic gastric digestion approaches simulate in vivo conditions more closely which especially impacted the rate of digestion.

In-depth insight into the effects of tapioca or corn acetylated distarch phosphate on the gel properties and in vitro digestibility of kung-wan

Modified starch is increasingly applied in the meat industry as an effective functional ingredient to provide meat products with the desired textural properties and appearance. This study aimed to investigate the effects of incorporating tapioca acetylated distarch phosphate (TADSP) or corn acetylated distarch phosphate (CADSP) on the gel properties and in vitro digestibility of Chinese-style meatballs known as kung-wan. The results showed that TADSP and CADSP significantly enhanced the textural properties of kung-wan in a dose-dependent manner (P < 0.05), as well as enhanced the rheological behavior of meat batters. TADSP resulted in a denser meat protein gel network compared to CADSP, primarily because the lower pasting temperature of TADSP made it gelatinize earlier and more completely during heating than CADSP and subsequently filled in the meat protein gel network. The intermolecular forces observed in kung-wan with TADSP or CADSP were hydrogen bonds and hydrophobic interactions. Furthermore, the protein digestibility of kung-wan was increased with higher levels of TADSP and CADSP (P < 0.05). Notably, kung-wan with TADSP exhibited significantly higher protein digestibility than those with CADSP at the same level (P < 0.05). Our results offer valuable insights into the potential application of acetylated distarch phosphate in kung-wan.

In vitro protein digestibility of different soy-based products: effects of microstructure, physico-chemical properties and protein aggregation

This study investigates the effects of protein structure and food microstructure on the in vitro protein gastrointestinal digestibility of different soy-based products, such as soy drink, reconstituted soy drink powder, firm tofu, and yuba. The results of the chemical cross-linking analysis showed that hydrogen bonds and hydrophobic interactions were the main forces driving protein aggregation in (reconstituted) soy drink powder and firm tofu, whereas disulphide bonds were significantly more important for soy drink and yuba. The β-sheet content of soy drink (36.5%) was lower than that of yuba (43.3%), but significantly higher than those of soy drink powder (23.2%) and firm tofu (29.8%). The in vitro protein digestibility decreased in the order of firm tofu > reconstituted soy drink powder > yuba > soy drink. Principal component analysis showed that protein gastrointestinal digestibility was positively correlated with the surface SH content and soluble protein content released by SDS + urea (SB-SA) but negatively correlated with the disulphide bonds and β-sheet content for the four soybean products.

Assessing the nutritional quality of lipid components in commercial meal replacement shakes using an in vitro digestion model

This study aimed to investigate the nutritional value of five commercial meal-replacement shakes, and mainly focused on the lipid digestion fates and fat-soluble vitamin bioavailability. Four out of five samples exhibited a low lipolysis level (37.33-61.42%), aligning with the intended objectives of these products. Although the remaining sample rich in diacylglycerol (DAG) had a higher lipolysis level (80.83%), the inherent low-calorie nature of DAG might compensate for this drawback. The release level of individual fatty acid was largely determined by the glycerolipid composition. Moreover, the strong positive correlation between lipid hydrolyzed products amounts and the fat-soluble vitamin bioavailability was observed. Surprisingly, one out of five samples can provide enough vitamin A and vitamin E for consumers as a total replacement of one or two regular meals. Consequently, the meal-replacement shakes hold the potential to emerge as healthy products for this fast-paced era if the composition and structure were carefully designed and calculated.

In-Depth Insight into the Mechanism of Incorporation of Abelmoschus manihot Gum on the Enhancement of Gel Properties and In Vitro Digestibility of Frankfurters

This study aimed to investigate the effects of different concentrations (0.1, 0.2, 0.3, 0.4, and 0.5% w/w) of Abelmoschus manihot gum (AMG) on the gel properties and in vitro digestibility of frankfurters. The results indicated that AMG incorporation significantly enhanced the emulsion stability and texture of frankfurters, as well as the dynamic rheological characteristics of raw meat batter, with the optimal concentration being 0.3% (p < 0.05). Furthermore, hydrogen bonds and disulphide bonds were the main molecular forces of the frankfurters in the presence of AMG. Microstructural images showed that more uniform and dense microstructures of frankfurters were formed due to AMG supplementation. In addition, AMG incorporation significantly increased the in vitro protein digestibility of frankfurters as the level of addition increased (p < 0.05). In conclusion, our results provided critical information for the practical application of AMG in the production of emulsified meat products.

Mechanisms underlying the effects of ultrasound-assisted alkaline extraction on the structural properties and in vitro digestibility of Tenebrio molitor larvae protein

Edible insects have been considered as a sustainable and novel protein source to replace animal-derived proteins. The present study aimed to extract Tenebrio molitor larvae proteins (TMP) using ultrasound-assisted alkaline extraction (UAE). Effects of different UAE times (10, 20, 30, 40, and 50 min) on the structural properties and in vitro digestibility of TMP were comparatively investigated with the traditional alkaline extraction method. The results revealed that ultrasonication could effectively alter the secondary/tertiary structures and thermal stability of TMP during UAE. The molecular unfolding and subsequent aggregation of TMP during UAE were mainly attributed to the formation of disulfide bonds and hydrophobic interactions. Moreover, TMP extracted by UAE had higher in vitro digestibility and digestion kinetics than those extracted without ultrasound, and the intermediate UAE time (30 min) was the optimal ultrasound parameter. However, longer UAE times (40 and 50 min) lowered the digestibility of TMP due to severe protein aggregation. The present work provides a potential strategy for the extraction of TMP with higher nutritional values.

Importance of adapted digestion conditions to simulate in vitro lipid digestion of broilers in different life stages

In vitro digestion studies demonstrate large potential to gain more and quicker insights into the underlying mechanisms of feed additives, allowing the optimization of feed design. Unfortunately, current in vitro digestion models relevant for broiler chickens lack sufficient description in terms of protocols and standardisation used. Furthermore, no distinction is made between the different life phases of these animals (starter, grower, and finisher). Hence, our research aimed to establish adapted in vitro digestion conditions, corresponding to the 3 life phases in broilers, with specific focus on lipid digestion. The effect of 3 different bile salt concentrations of 2, 10, and 20 mM, and 3 different lipase activities of 5, 20, and 100 U/mL, on in vitro lipid digestion kinetics were evaluated using a full factorial design. These values were selected to represent starter, grower, and finisher birds, respectively. Our findings showed that the extent of lipid digestion was mainly influenced by lipase activity. The rate of lipid digestion was affected by an interplay between bile salt concentration and lipase activity, due to possible lipase inhibition at certain bile salt concentrations. Overall, this work resulted in 3 in vitro lipid digestion models representative for starter, grower, and finisher birds. In conclusion, this research showed the impact of adapted in vitro digestion conditions on lipid digestion kinetics and thus the need for these conditions relevant for each life phase of broilers.

Studying semi-dynamic digestion kinetics of food: Establishing a computer-controlled multireactor approach

In this work, a multireactor system to study digestion (MuReDi) kinetics is introduced. For this, a custom-made automated system with four independent syringe pumps (BioXplorer 100, H.E.L Group) was acquired. This system consists of multiple, small-scale reactors allowing to study digestion as a function of time and thus to determine digestion kinetics. The different digestion conditions used in the oral, gastric, and small intestinal phase were based on the digestion protocols published by the INFOGEST consortium. We showed that the minimum working volume of a reactor is 30 mL. Besides, repeatability of the digestion kinetics was shown for two food systems: a liquid Ensure® Plus Vanilla drink, and a solid, cooked lentil sample. When comparing static digestion kinetics with semi-dynamic ones, a significantly different digestion pattern was observed. In the static case, a relatively fast hydrolysis rate was observed until a clear plateau was reached. Oppositely, for the semi-dynamic case, a delayed start of the hydrolysis process was noticed. In the gastric phase, this was explained by the decreasing pH and the large pH dependency of pepsin activity. In the small intestine, the lag phase was relatively shorter, yet clearly present. Here we related it to the gradual enzyme (and bile salt) secretion that had to diffuse towards the substrate before hydrolysis could start. Generally, this work showed that the MuReDi system could be used to perform a semi-dynamic digestion approach which largely impacted the overall digestion kinetics. This is important to consider in future in vitro food digestion simulation work to come closer to physiologically relevant digestion kinetics.