Three-dimensional (3D) printing is a rapidly developing additive manufacturing technique consisting of the deposition of materials layer-by-layer to produce physical 3D structures. The technique offers unique opportunities to design and produce new products that cater to consumer experience and nutritional requirements. In the past two decades, a wide range of materials, especially plant-protein-based materials, have been documented for the development of personalized food owing to their nutritional and environmental benefits. Despite these benefits, 3D printing with plant-protein-based materials present significant challenges because there is a lack of a comprehensive study that takes into account the most relevant aspects of the processes involved in producing plant-protein-based printable items. This review takes into account the multi-dimensional aspects of processes that lead to the formulation of successful printable products which includes an understanding of rheological characteristics of plant proteins and 3D-printing parameters, as well as elucidating the appropriate concentration and structural hierarchy that are required to maintain stability of the substrate after printing. This review also highlighted the significant and most recent research on 3D food printing with a wide range of plant proteins. This review also suggests a future research direction of 3D printing with plant proteins.

This review summarizes and critically analyze the scientific studies pertinent to three-dimensional printing of plant-proteins based meat-analog. Vegetable proteins, oils, and water are the major ingredients in formulating ink for three-dimensional printing of meat-analogs; while, hydrocolloid, enzyme, yeast, colorant, mineral, flavor, etc. are used as minor ingredients. Both ingredients and formulation modulate rheological properties of the ink, and consequently three-dimensional printing's performance and post-printing stability of the meat-analogs. Printing temperature, contact angle, nozzle height, nozzle diameter, layer height, and speed of nozzle movement are the most critical parameters that influence printing of meat-analogs. Air heating, baking, steaming, deep-fat frying, and microwave heating have been successfully used to finish-cook three-dimensional printed meat-analogs. Micro-structural characteristics and ingredient's distribution impact functionalities and stability of printed analogs. Safety aspects, legal frameworks, and sustainability issues should be taken as major concern. Future research directions pertinent to three-dimensional printing of plant-based meat-analog, have been identified.

Food surface modulation by batter coating is a promising approach to reduce the presence of oil in fried products. This review critically discussed the functionalities, mechanism of actions, rheology, ingredients of formulation, mathematical modeling of the process, cooking method, safety and regulatory aspects, physicochemical, thermal-microstructural characterization of batter coatings, and future research directions. Enormous list of ingredients could be used in preparation of oil-reducing viscoelastic batter coating that includes mostly flours, hydrocolloids, and starches. Bioactive compounds, enzymes, minerals, herbal extracts, baking agents, sugar alcohols, etc. could be incorporated in batter formulation to affect the taste and texture of coated products. Overall mass-transfer process of batter-coated fried foods could be characterized by several mathematical models (Fick, Newton, Page, Henderson & Pabis, modified Page, Arrhenius). Surface and internal microstructural characterization techniques, thermal probing, physicochemical characterization techniques and artificial intelligence can characterize different functionalities of batter coatings including oil reduction and textural evolution.

Surface characterization of food products is critical for understanding their physical, chemical, and biological properties, which have a direct impact on quality, safety, and consumer acceptability. Scanning electron microscopy (SEM) paired with "fractal analysis" has developed as an effective method for studying food surfaces at the micro- and nanoscales. This review investigated the use of SEM to examine the topographical features of various food items, such as fruits, vegetables, grains, and processed foods, emphasizing the importance of surface morphology in determining texture, moisture retention, and overall product quality during consumption and storage. Fractal analysis, together with SEM, is a quantitative approach for describing the complexity of foods surface structures. Fractal and multifractal analysis using SEM images yields a numerical description of surface roughness, complexity, and heterogenicity. The combination of SEM with fractal analysis not only allows for a more in-depth study of food surface characteristics, but it also helps to optimize food processing procedures. Positive correlations between processing (drying, frying, freezing) time, fractal dimension, and surface openings have been established. Fractal dimension of various food items (fruit, vegetable, crispy product, powder, extrudate product, puffed food, frozen product, fish, etc.) and their characteristics quality attributes have been found expressively interlined. The outcomes of multifractal analysis (Singularity and Rényi spectra) successfully characterized heterogenicity in foods surface micro-structure. SEM image-based fractal analysis, which reveals the subtle links between surface morphology and food attributes, showed potential to significantly expand food science and technology, paving the door for advances in food processing and quality management.

This study aimed to characterize the thermomechanical transitions of meat-analog (MA) based coated fried foods. Wheat and rice flour-based batters were used to coat the MA and fried at 180 °C in canola oil for 2, 4 and 6 min. Glass-transition-temperature (Tg) of the coatings were assessed by differential scanning calorimetry, directly after frying or after post-fry holding. Mechanical texture analyzer and X-ray microtomography were employed to assess textural attributes and internal microstructure, respectively. Batter-formulation substantially impacted the Tg of fried foods coating i.e., crust. Tg of fried foods crust were ranged between -20 °C to -24 °C. Tg was positively correlated with frying time and internal microporosity (%), whereas negatively correlated with moisture content. Internal microstructure greatly influenced the textural attributes (hardness, brittleness, crispiness). Post-fry textural stability considerably impacted by Tg. Negative Tg value explains post-fry textural changes (hard-to-soft, brittle-to-ductile, crispy-to-soggy) of MA-based coated products at room-temperature (25 °C) and under IR-heating (65 °C).