Zhiyun Zhang

Plant-based seafood analogs are gaining increasing popularity as replacements for traditional fish and other seafood products due to environmental (stock depletion, pollution, and bycatch issues) and health (bioaccumulated toxins, norovirus, and allergies) concerns associated with them. Several companies have launched plant-based fish products, but the market still lacks alternatives to shellfish and other sea delicacies. In this study, a plant-based sea foie gras (monkfish liver product) analog was developed using duckweed RuBisCO protein and omega-3-rich flaxseed oil to form emulsion gels. These gels consisted of a high concentration of flaxseed oil droplets dispersed within a gelled RuBisCO protein network. It was hypothesized that the high disperse phase volume fraction of the oil droplets and the heat-set gelation properties of the RuBisCO proteins would enable us to create emulsion gels that mimicked the properties of sea foie gras. A natural pigment (β-carotene) was incorporated into the oil phase of the emulsions to mimic the red-orange color of conventional sea foie gras. The structural, textural, and optical properties of real and plant-based sea foie gras analogs were characterized using scanning electron microscopy, confocal microscopy, dynamic shear rheology, texture profile analysis, and colorimetry. Emulsion gels prepared using 40% flaxseed oil and 10% RuBisCO proteins produced plant-based products that closely simulated the texture and color of the real products. Rheological analysis suggested that the oil droplets acted as active fillers within the protein gels. Our results suggest that emulsion gels may be used to create more sustainable and healthier plant-based seafood products.

Concerns exist regarding the negative environmental impact and health risks associated with ocean fishing and aquaculture, such as stock depletion, pollution, biodiversity loss, and toxin presence. To address these concerns, plant-based seafood analogs are being developed. Our previous study successfully created plant-based scallop analogs using pea proteins and citrus pectin, resembling real scallops in appearance and texture. This study focuses on comparing the digestive fate of these analogs to real scallops, as it can impact their nutritional properties. Using an in vitro digestion model (INFOGEST), we simulated oral, gastric, and small intestinal conditions. The analysis revealed differences in the microstructure, physicochemical properties, and protein digestibility between the plant-based scallops and real scallops. The particle size and charge followed the following similar trends for both types of scallops: the particle size decreased from the mouth to the stomach to the small intestine; the particles were negative in the mouth, positive in the stomach, and negative in the small intestine. The protein digestibility of the plant-based scallops was considerably lower than that of real scallops. For instance, around 18.8% and 61.4% of protein was digested in the stomach and small intestine phases for the real scallop (80.2% total digestion), whereas around 8.7% and 47.7% of the protein was digested for the plant-based scallop (56.4% total digestion). The lower digestibility of the plant-based scallops may have been due to differences in the protein structure, the presence of dietary fibers (pectin), or antinutritional factors in the plant proteins. These findings are crucial for developing more sustainable next-generation plant-based seafood analogs.

This study investigated the possibility of using a phase separation, mixing, and enzymatic gelation approach to construct seafood analogs from plant protein-polysaccharide mixtures with properties mimicking real seafood. Heat-denatured pea protein (10%, w/w) and pectin (0–1%, w/w) were mixed to produce phase separated biopolymer blends. These blends were then subjected to mild shearing (350 rpm) to obtain fiber-like structures, which were then placed in molds and set by gelling the pea proteins using transglutaminase (2%, w/w). The appearance, texture, and cooking properties of the resulting scallop analogs were characterized and compared to those of real scallop. The presence of the pectin promoted the formation of a honeycomb structure in the scallop analogs, and microscopic orientation of the proteins was observed in the plane parallel to the applied shear flow. Lower pectin concentrations (0.5%, w/w) led to stronger gels with better water holding capacity than higher ones (1.0%, w/w). The appearance and texture of the plant-based scallop analogs were like those of real scallop after grilling, indicating the potential of using this soft matter physics approach to create plant-based seafood analogs. One of the main advantages of this method is that it does not require any expensive dedicated equipment, such as an extruder or shear cell technology, which may increase its commercial viability.

Understanding the behavior and biological fate of silver nanoparticles (AgNPs) applied on plant surfaces is significant for their risk assessment. Our study's objective is to investigate the interactions between AgNPs and plant biomolecules as well as to monitor and quantify the penetration of AgNPs in spinach by an in situ and real-time surface enhanced Raman spectroscopic (SERS) mapping technique. AgNPs (2 μg per leaf) of different surface coatings (citrate, CIT, and polyvinylpyrrolidone, PVP) and sizes (40 and 100 nm) were foliarly applied onto spinach leaves with different exposure times (1–48 h). Cysteine is the major biomolecule that interacts with AgNPs in spinach based on the in situ and in vitro SERS pattern recognition. The interaction between CIT–AgNPs and cysteine happened in as early as 1 h after AgNP foliar deposition, which is faster than the interaction between PVP–AgNPs and cysteine. Also, the SERS depth mapping shows that particle size rather than surface coating determines the penetration capability of AgNPs in spinach, in which 40 nm AgNPs show a deeper penetration than the 100 nm ones. Last but not least, based on the results of SERS mapping, we detected significantly higher amounts of 40 nm CIT–/PVP–AgNPs than 100 nm CIT–AgNPs internalized in the leaf tissues after 1 h exposure. The estimated percentage of internalized AgNPs (0.2–0.8%) was significantly smaller than that of the total residual Ag (9–12%), indicating the potential transformation of the AgNPs into other Ag species inside the plant tissues. This study facilitates a better understanding of the behavior and biological fate of AgNPs in plant tissues.

We systematically investigated the impact of oil droplet diameter (≈0.15, 1.6, and 11 μm) on the bioaccessibility of three oil-soluble vitamins (vitamin A palmitate, vitamin D, and vitamin E acetate) encapsulated within plant-based emulsions.

Many plant-based milks lack key micronutrients found in bovine milk, such as calcium and vitamin D. In this study, we fortified almond milk with these two micronutrients and used a standardized gastrointestinal model to examine the impact of product formulation on their bioaccessibility. The impact of different forms (CaCl₂ versus CaCO₃) and concentrations (0, 1, or 2 g per 240 mL) of calcium on the physicochemical properties, lipid digestibility, and vitamin D bioaccessibility was examined. Soluble calcium (CaCl₂) promoted particle aggregation by reducing the electrostatic repulsion, while colloidal calcium (CaCO₃) did not because there were fewer free calcium ions. High levels of calcium (soluble or insoluble) reduced vitamin D bioaccessibility, which was attributed to insoluble calcium soap formation in the small intestine. Calcium bioaccessibility was higher for CaCO₃ than CaCl₂. These findings are useful for the development of nutritionally fortified plant-based milks with improved physicochemical and nutritional properties.

The oil droplets in commercial emulsified foods have dimensions that vary widely, from hundreds of nanometers to tens of micrometers. Previously, the size of the droplets in oil-in-water emulsions has been shown to impact their gastrointestinal behavior, which may influence their physiological effects. In this study, we analyzed the impact of oil droplet diameter (0.16, 1.1 and 8.2 μm) on lipid digestion and nutraceutical bioaccessibility using a widely used standardized gastrointestinal tract model: the INFOGEST method. The emulsions used consisted of corn oil droplets stabilized using a food-grade non-ionic surfactant (Tween 20), and the droplet size was controlled by preparing them with a microfluidizer (small), sonicator (medium), or high-shear blender (large). The surfactant-coated oil droplets were relatively resistant to size changes in the mouth and stomach, due to the strong surface activity and steric stabilization mechanism of the non-ionic surfactant used. As expected, the kinetics of lipid digestion were enhanced for smaller droplets because of their greater specific surface area. The degree of lipid digestion fell from 117% to 78% (p < 0.001) as the initial droplet diameter was raised from 0.16 to 8.2 μm. In addition, there was a reduction in β-carotene bioaccessibility from 83 to 15% (p < 0.001) with increasing droplet diameter. This result was ascribed to several effects: (i) some carotenoids were trapped inside the undigested oil phase; (ii) fewer mixed micelles were produced to internalize the carotenoids; and, (iii) a fraction of the carotenoids crystallized and sedimented. Our results underline the critical importance of considering droplet size when developing emulsified foods loaded with carotenoids. The results obtained by the INFOGEST method are consistent with those found using other in vitro methods in earlier studies.