Danyang Ying

Expanded snack extrusion is governed by tightly coupled interactions among raw material composition, moisture, barrel temperature, screw speed, feed rate, screw configuration, die geometry, and energy input. These variables affect not only final responses such as expansion ratio, bulk density, hardness, crispness, and water absorption or solubility indices, but also intermediate state variables including specific mechanical energy (SME), melt temperature, die pressure, melt viscosity, and bubble growth dynamics. As a result, modelling has become essential for product design, process optimisation, and scale-up. This review critically evaluates the major classes of models used to describe process–structure–quality relationships in the extrusion of expanded snacks. The literature shows that empirical regression and response surface methodology (RSM) remain the most widely applied tools because they are experimentally efficient and easy to interpret. However, mixture-process designs are more appropriate when formulation and operating variables are changed simultaneously, while phenomenological and mechanistic approaches provide better physical insight into expansion and structure development. More recently, machine-learning and interpretable artificial intelligence approaches have demonstrated strong predictive capability when large, well-curated datasets are available. Across model families, a consistent theme is that operating variables act on final product quality through intermediate process state variables rather than independently. On that basis, this review proposes a practical hybrid framework for expanded snack extrusion: a mixture-process quadratic model augmented with SME, die pressure, melt temperature and shear-related state variables, and structured in three levels linking (i) controllable inputs to state variables, (ii) state variables to measurable quality attributes, and (iii) quality attributes to a gold-standard product target or sensory-control criterion. Such a model offers a realistic balance between predictive performance, physical interpretability, experimental burden, and industrial usefulness, while also providing a clear pathway toward future digital twin and machine-learning-enabled optimisation.

This study aimed to develop a microencapsulation formulation for efficient encapsulation of β-glucosidase to improve its stability in a rumen-like environment and sustain activity post-rumen in the ruminant gut. Various alginate-based formulations were evaluated to achieve high encapsulation efficiency (EE) and stability. These included control alginate beads (AB), microcapsules with chitosan (MCS), alginate–sucrose beads (AOS), alginate–sucrose–maltodextrin beads (AOMS), and alginate pectin beads (APB). The microcapsules were made using Buchi encapsulator B-390 with calcium chloride as the gelling solution. Alginate proved to be a suitable polymer for β-glucosidase encapsulation and <1 mm diameter microbeads were obtained across all formulations. Alginate alone (AB: 1% alginate, 0.2 U/mL β-glucosidase) showed low EE (3% ± 1.0) due to leakage and syneresis. Modifying the gelling solution with 0.1% chitosan (MCS) increased EE to 49 ± 2.64% by reducing alginate porosity. Further improvements were achieved by adding stabilizers to the alginate solution (AB), in addition to using the modified gelling solution (MCS): Adding sucrose (AOS) at 4% increased EE to 95.5 ± 2.08%, while adding sucrose (4%) and maltodextrin (2%) (AOMS) achieved 100 ± 2.16%. On the other hand, adding pectin (4%) (APB) to the alginate solution resulted in a lower EE of 40.5% ± 2.55, likely due to interference with alginate crosslinking. In vitro rumen fermentation showed a dry matter degradation of 42–54%, underscoring the need for more robust microcapsules. Encapsulation strategies, such as incorporation of additional protective layers, are essential to enhance bead stability, minimize degradation, and improve enzyme retention, to ensure efficient delivery and sustained enzymatic activity in the hindgut.

The need for effective enzyme delivery systems in ruminant nutrition is underscored by the challenge of protecting enzymes in the harsh rumen environment. This study focused on enhancing the encapsulation efficiency (EE) of β-glucosidase in alginate beads to improve its stability and protection within rumen-like conditions. The objective was to develop a microencapsulation system capable of sustaining enzyme activity post-ingestion, using β-glucosidase as a model enzyme. Various formulations were tested to optimize EE and stability. Data were collected by systematically incorporating different stabilizers and crosslinking agents into the alginate matrix. The addition of 0.1% chitosan into the gelling solution significantly improved EE to 49% by reducing the matrix’s porosity. Further improvements were achieved with stabilizers: 4% sucrose (AOS) increased EE to 95.5%, while the combination of 4% sucrose and 2% maltodextrin (AOMS) reached the highest EE at 100 ± 2.16%. In contrast, the addition of 4% pectin (APB) reduced EE to 40.5%, likely due to interference with alginate crosslinking and higher water content, weakening bead structure.In vitro rumen fermentation tests showed degradation rates of 42–54%, highlighting the need for further development of more robust microcapsules. These findings suggest that additional coating strategies are essential to improve bead stability in rumen environments. Future research should focus on creating bead formulations with enhanced protective layers to increase enzyme retention and recovery during delivery.

This study investigates the impact of dry heat pretreatment on the functionality of soy, chickpea, and pea protein ingredients for use in texturized vegetable protein (TVP) production via low moisture extrusion. The protein powders were heat-treated at temperatures ranging from 80 °C to 160 °C to modulate the extent of protein denaturation and assess their effects on RVA pasting behavior, water absorption capacity (WAC), and color attributes. The results indicate that the pretreatment temperature significantly influenced the proteins’ functional properties, with an optimal temperature of 120 °C enhancing pasting properties and maintaining WAC, while a higher pretreatment temperature of 160 °C led to diminished ingredient functionality. Different protein sources exhibited distinct responses to heat pretreatment. The subsequent extrusion processing revealed significant changes in extrudate density and color, with increased density and darkness observed at higher pretreatment temperatures. This research provides insights into the interplay between protein sources, pretreatment conditions, and extrusion outcomes, highlighting the importance of controlled protein denaturation for developing high-quality, plant-based meat analogues. The findings have broad implications for the optimization of meat analogue manufacturing, with the aim of enhancing the sensory experience and sustainability of plant-based foods.

Perishable fresh vegetables that do not meet cosmetic standards and by-products of processing are currently wasted. Broccoli and carrots were selected as model vegetables to demonstrate that they can be converted into nutrient-dense and shelf-stable food ingredients and formulated into convenient ready-to-eat snacks. Broccoli powder was a rich source of protein (30%) and dietary fibre (28%). Carrot powder had lower protein (6.5%) and dietary fibre content (24%) and was higher in sugar (47%) compared to broccoli powder (21%). Compared to the whole-vegetable powders, pomace powders were richer in fibre but had lower levels of total carbohydrates. There was a reduced expansion of extruded snacks with increasing levels of the vegetable component in the formulation. Processing and storage for 12 months at 25 °C or 40 °C resulted in changes in the measured soluble phenolic content. Changes during storage were dependent on the temperature and time. The changes may be in part due to the changes in the material properties of the matrix as a consequence of processing and storage, which affect extractability. The conversion of perishable vegetables and pomace into shelf-stable nutrient-dense food ingredients and products will reduce food loss and waste in the vegetable industry.