Nucleation and Expansion During Extrusion and Microwave Heating of Cereal Foods

Unlocking the potential of pasting properties to predict extrudate characteristics of corn grits blends with high amylose corn starch, potato starch, or rice flour

The development of new production lines of extruded ready-to-eat (RTE) snacks often results in high losses of edible food due to the trial-and-error approach in industry. Being able to predict extrudate characteristics of new formulations before having to run trials on industrial scale would be beneficial for reducing waste and having a more efficient development process. With this study, the correlation between pasting properties of seven blends of flours/starches and extrudate characteristics was investigated (100% corn grits, 25% and 50% replacement of corn grits with high amylose starch, potato starch, and rice flour). The predictive power of pasting characteristics on extrudate's moisture content, water absorption and solubility index, sectional expansion index (SEI) and hardness was studied. Results indicated the potential of predicting SEI, water solubility index (WSI), and water absorption index (WAI) of RTE-snacks. WSI and WAI were, respectively, negatively correlated with peak temperature (R2  = 0.897), and positively with peak temperature and positively with trough viscosity (R2  = 0.855). One can conclude that the rheometer can be a useful tool to gain insight into the characteristics of the extrudate, although further research with enlargement of the dataset is necessary to make the rheometer effectively deployable for potentially other extrudate characteristics.

Expanded porous-starch matrix as an alternative to porous starch granule: Present status, challenges, and future prospects

Exposing the hydrated-soft-starch matrix of intact grain or reconstituted flour dough to a high-temperature-short-time (HTST) leads to rapid vapor generation that facilitates high-pressure build-up in its elastic matrix linked to large deformation and expansion. The expanded starch matrix at high temperatures dries up quickly by flash vaporization of water, which causes loss of its structural flexibility and imparts a porous and rigid structure of the expanded porous starch matrix (EPSM). EPSM, with abundant pores in its construction, offers adsorptive effectiveness, solubility, swelling ability, mechanical strength, and thermal stability. It can be a sustainable and easy-to-construct alternative to porous starch (PS) in food and pharmaceutical applications. This review is a comparative study of PS and EPSM on their preparation methods, structure, and physicochemical properties, finding compatibility and addressing challenges in recommending EPSM as an alternative to PS in adsorbing, dispersing, stabilizing, and delivering active ingredients in a controlled and efficient way.

Mung Bean Starch and Mung Bean Starch Sheet Jelly: NaCl-Based Characteristics Variation

Empirical evidence indicates that NaCl can improve the quality of mung bean starch sheet jelly (MBSS) when properly incorporated. In this study, by comparison with a sample without NaCl, the influences of NaCl (1.5-8%, w/w) on the physicochemical and structural properties of mung bean starch (MBS) and the quality of MBSS were investigated. MBS with added NaCl had greater gelatinization temperature and pasting parameters but lower gelatinization enthalpy than native MBS. With the addition of NaCl, the drying rate of MBSS first accelerated and then declined in the oven-drying process. The addition of NaCl improved the cooking properties of MBSS but decreased the hardness of cooked MBSS. Rheological results implied that the linear viscoelastic region of cooked MBSS decreased with the NaCl addition, and the storage modulus and tan δ were more frequency-dependent than the loss modulus of cooked MBSS. The addition of NaCl gradually increased the toughness of dried MBSS and the overall acceptability of cooked MBSS. Furthermore, NaCl decreased the structure order degree of starch in MBSS. Correlation analysis demonstrated that the quality of MBSS had a significant correlation with the molecular and lamellar order of starch. Overall, NaCl could improve the quality of MBSS by regulating the thermal, gelatinizing, and structural properties of MBS.

Evaluation of the Physical, Chemical, Technological, and Sensorial Properties of Extrudates and Cookies from Composite Sorghum and Cowpea Flours

In recent years, there has been a growing demand for gluten-free and functional products, driven by consumer preferences for healthier and more diverse food choices. Therefore, there is a need to explore new ingredients that can be used as alternatives to traditional gluten-containing grains. Thus, this work evaluated the physical, chemical, technological, and sensorial properties of extrudates and cookies from composite tannin sorghum (rich in resistant starch) and white cowpea flours. Extrudates and cookies were produced from a composite flour made of sorghum and cowpea, at a sorghum:cowpea flour ratio of 70:30, 50:50, and 30:70. Then, raw flours, cookies, and extrudates were characterized (dietary fiber, resistant starch, proteins, antioxidant capacity, pasting properties, etc.). Results obtained for particle size distribution and bulk density indicated that the particles increased and the color changed with the addition of cowpea flour. The raw tannin sorghum flour had a higher resistant starch concentration (36.3%) and antioxidant capacity (211.2 µmolTE/g), whereas cowpea flour had higher levels of proteins (18.7%) and dietary fiber (20.1%). This difference in the raw flour composition contributed to the nutritional value of the extrudates and cookies, especially the cookies which undergo dry heat and had higher retention of resistant starch and antioxidants. Moreover, sorghum flour presented a higher tendency to retrograde (high setback), which was decreased by the addition of cowpea flour. Overall acceptance and intention to purchase were higher for extrudates with 100% sorghum flour (6.52 and 68.3%, respectively) and cookies with 70% cowpea flour (7.03 and 76.7%, respectively). Therefore, nutritious and functional gluten-free extrudates and cookies, of good acceptability, can be produced from composite tannin sorghum and white cowpea flours.

Physicochemical characteristics and structural changes of fermented faba bean extrudates prepared by twin-screw extrusion

In this study, fermented faba bean blends with different locust bean gum (LBG) contents were processed in a co-rotating twin-screw extruder. The effects of extrusion process variables and the LBG level on physicochemical, sensory and structural characteristics of expanded extrudates were investigated. The results showed that physical characteristics of extrudates including expansion, apparent density and texture were significantly affected by variation of screw speed and die temperature, but the effect of LBG level was only significant for expansion and density. FTIR-ATR analysis revealed that a significant change occurred in the protein secondary structure as well as in the short-range ordered molecular structure of starch during fermentation and extrusion. The X-ray diffraction patterns of extrudates exhibited V-type pattern. Microstructure of the extrudates analyzed by FE-SEM exhibited variations in cell size and wall thickness depending on extrusion processing conditions and LBG level, which in turn lead to different textural perceptions.

Effect of Citrus Pellet on Extrusion Parameters, Kibble Macrostructure, Starch Cooking and In Vitro Digestibility of Dog Foods

Fiber supplemented extruded foods are produced by pet food companies to help with several specific health conditions. The fiber material, however, is difficult to incorporate efficiently into dry kibble diets for dogs. The aim of the study was to evaluate the influence of citrus pulp pellet (CPP), the solid waste part of the production of orange juice characterized by a good proportion of soluble and fermentable fiber, on extrusion traits, kibble macrostructure, starch gelatinization and in vitro digestibility of dog foods. A control formula (CO) was developed for dogs. CPP was added to CO at different inclusion levels: 5%, 10%, 15% and 20%. Foods were extruded in a single screw extruder using two different die diameters (d_d): 5 mm and 7 mm. CPP inclusion with 5 mm d_d did not affect bulk and piece density and resulted in a lower impact on kibble expansion; It also resulted in greater starch gelatinization and kibble expansion compared to the 7 mm d_d configuration (p < 0.01). In addition to the nutritional implications, recycling and proper uses of this material exemplified in the present study by the exploration of CPP as a fiber source to dogs, this method can improve sustainable agriculture by transforming low-quality materials into high-quality foods.

Effects of boiling and steaming process on dietary fiber components and in vitro fermentation characteristics of 9 kinds of whole grains

Whole grains (WGs) are considered as the representative sources of dietary fiber (DF). Thermal treatments can change the properties of DF, and potentially affecting the gut microbiota as well as human health. In this study, DF content and in vitro fermentation characteristics of 9 kinds of WGs (highland barley, barley, buckwheat, proso millet, quinoa, sorghum, coix seed, foxtail millet, and oats) after boiling and steaming treatments were compared. It was found that boiling and steaming treatments could both increase DF content in these grains, except for barley and foxtail millet. Processed WGs could regulate beneficial microbial genus, such as Bifidobacterium, Prevotella, Megamona and Megasphaera. Oats, quinoa, highland barley, and buckwheat after boiling treatment can produce more total short-chain fatty acids (SCFAs) than steaming treatment (p < 0.05), while barley, foxtail millet and coix seed showed opposite results. This study can provide data support for the design of WGs diets and the development of WGs products which are beneficial for gut health.

Novel Gluten-Free Breakfast Cereals Produced by Extrusion Cooking from Rice and Teff: Effects on Microstructural, Physical and Nutritional Properties

Current gluten-free products often have nutritional inadequacies. Teff is generating a growing interest for its excellent nutritional value. In this study, the effects of teff enrichment of extruded gluten-free breakfast cereals based on rice flour and two process parameters-feed moisture and temperature-were investigated based on their physical, microstructural and nutritional properties. The independent variables were modulated and examined by a Box-Behnken design. The incorporation of teff flour affected the sensory properties of extruded cereals, particularly lightness and crispness, with estimated linear effects of -6.91 and -8.49, respectively. The enrichment of breakfast cereals with teff flour also increased the total phenolic content and antioxidant capacity in both free and bound fractions, as well as the amount of insoluble dietary fibre. By varying all independent variables, the microstructural and physical properties of samples changed considerably. At the lowest feed moisture, wall thickness was small while showing the highest expansion. Samples with the highest teff flour addition exhibited an increased number of small pores which decreased crispness. These findings suggest that, by optimized extrusion cooking, the use of teff flour seems to be promising for the preparation of gluten-free breakfast cereals with superior nutritional properties and good structural characteristics.

Diet production and utilization of corn fermented protein compared to traditional yeast in healthy adult cats

The inclusion of yeast in pet food can provide health benefits and increase palatability. Corn fermented protein is a co-product from ethanol production which contains approximately 20% to 25% yeast. The objective of this study was to determine the effects of the yeast in CFP on diet production and utilization when fed to healthy adult cats. The four experimental diets included a control with 15% soybean meal (CON) and diets containing either 3.5% brewer's dried yeast (BDY), 2.5% brewer's dried yeast plus 17.5% distillers dried grains with solubles (BDY+DDGS), or 17.5% corn fermented protein (CFP). All treatments except CON were formulated to contain 3.5% yeast. Experimental diets were fed to adult cats (n = 11) in an incomplete 4 × 4 replicated Latin square design. Cats were adapted to diet for 9 d followed by a 5-d total fecal collection. Titanium dioxide (0.4%) was added to all diets as an external marker to estimate digestibility. Data were analyzed using a mixed model in SAS (version 9.4, SAS Institute, Inc., Cary, NC) with treatment as a fixed effect and cat and period as random effects. Preconditioner discharge temperature was greater (P < 0.05) for CON and BDY (average, 96 °C) compared to BDY + DDGS and CFP (average, 91 °C). Extruder screw speed, die temperature, kibble toughness, and kibble hardness were greatest (P < 0.05) for CFP. The bulk density of BDY + DDGS at 392 g/L was greater (P < 0.05) than BDY and CFP (average, 342 g/L). The sectional expansion index of kibble for CFP was greater (P < 0.05) than BDY + DDGS and smaller (P < 0.05) than CON but similar to BDY. Fecal output was greatest (P < 0.05) for cats fed BDY + DDGS. Nutrient digestibility was lowest (P < 0.05) for BDY + DDGS. The concentrations of short-chain and branched-chain fatty acids in fecal samples were not altered (P > 0.05) by dietary treatment. Cats had no preference (P > 0.05) when comparing CON to BDY or BDY + DDGS. However, cats consumed significantly less CFP compared to CON. The significant differences for bulk density, fecal output, and nutrient digestibility among dietary treatments are likely due to a greater fiber effect of DDGS compared to CFP. Therefore, the yeast component in CFP may provide greater kibble expansion and nutrient utilization compared to DDGS when fed to cats.

Valorization of Beetroot By-Products for Producing Value-Added Third Generation Snacks

Food waste is becoming a growing and important concern at both local and global levels. One-third of all food production is lost or wasted globally. It is necessary to look for alternatives that allow the use of agri-food waste or byproducts and that can provide value to other foodstuffs. The utilization of beetroot byproducts for producing value-added third generation (3G) snacks was the main aim of this work. These snacks are obtained by indirect expansion by extrusion and later heat expansion. In order to achieve this aim, a corn grits base was used and the influence of water content and beetroot byproduct content effect was studied on expansion kinetics by microwave energy and on texture, colour, extrusion parameters and bioactive compounds of expanded 3G snacks. The microwave expansion kinetics study determined the appropriate time to expand the formulations studied. Samples with higher water content in the mixtures needed more expansion time. In terms of expansion, all samples presented acceptable values; however, samples with 25% water in the mixtures showed better results. Furthermore, these snacks showed more crunchiness and less hardness. Beetroot byproduct incorporation provided additional functional value to the snacks. The betalains and phenols contained in the beetroot byproduct were presented in the expanded snacks and increased the antioxidant capacity of the snacks. With this study, it can be recommended to use 25% water content and 10% beetroot byproduct in corn mixture to obtain a third-generation snack with added value.

Food extrusion: An advanced process for innovation and novel product development

Extrusion is a versatile process capable of producing a variety of new and novel foods and ingredients, thus increasing manufacturing opportunities. Further, it could provide nutritious, safe, sustainable, and affordable foods, especially directed at individualized consumer needs. In addition to past research efforts, more investigations should be conducted in order to refine, redesign, or develop new extrusion processing technologies. The present review highlights the current advances made in new and novel food product development by considering the extrusion process, the influencing parameters, and product characteristics and properties; the most promising extrusion processes that can be used in novel food product and ingredient development, such as extrusion cooking, hot-melt extrusion, reactive extrusion, and extrusion-based 3D printing; the possibilities of using various raw materials in relation to process and product development; and the needs for product development modeling along with extrusion process design and modeling. In correlation with extruded product development, topics that merit further investigation may include structure formation, plant and animal biopolymers functionalization, biopolymer reactions, process simulation, modeling and control, engineering and mechanical aspects of extruders, analysis of pre-processing treatments, as well as prototyping, risk analysis, safety, sensory and consumer acceptance.

Butterfly Pea Flower as a Novel Ingredient to Produce Antioxidant-Enriched Yellow Pea-Based Breakfast Cereals

Butterfly pea flower (BP) is a rich source of bioactive components and can potentially be utilized to produce appealing, wholesome foods. Antioxidant and dietary fiber-enriched breakfast cereals were produced by extrusion cooking using blends of BP and yellow pea flour (YP). BP was added to YP at 0%, 5% and 10% levels (w/w), respectively, and extruded at two temperature profiles with die temperatures of 130 and 150 °C. Incorporation of BP significantly (p < 0.05) improved the total phenolics content, antioxidant properties, and insoluble and total dietary fiber content of the extrudates, with 10% BP extrudates showing the highest values. At a die temperature of 150 °C, the extrudates had a higher expansion ratio, a lower dry hardness, and a higher dry crispiness as compared to those at 130 °C. The color of BP-incorporated extrudates was darker and bluer as compared to the no-BP extrudates. The 10% BP extrudates retained relatively more of their hardness, crispiness, and crunchiness after soaking, indicating a better bowl-life and, therefore, better suitability of this blend formula for breakfast cereal production. Overall, this research shows that healthier breakfast cereals with appealing color and relatively longer bowl-life can be produced using BP, making BP a potential novel ingredient for extrusion formulations.

Extrusion puffing pretreated cereals for rapid production of high-maltose syrup

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Extrusion puffing of cereals improved their water solubility and gelatinization.

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FTIR-ATR study revealed structural differences between native and puffed cereals.

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Extrusion puffing highly enhanced the efficiency of saccharification.

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The extruded-puffed cereals had a higher V_max/K_m value as compared to native.

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Extruded-puffed cereals showed potential for high-maltose syrup production.

In this study, cereals with high starch content, including brown rice, corn, and buckwheat were pretreated by extrusion. The physicochemical properties of extruded-puffed cereals obtained from different extrusion conditions were analyzed herein. The puffed extrudates exhibited lower bulk density, higher water solubility and gelatinization as compared to untreated cereals. The FTIR-ATR results confirmed a decrease in the crystalline structure of extruded-puffed cereals. A higher V_max/K_m value was observed in the enzymatic saccharification of puffed extrudates that significantly improved hydrolysis rate and yield. Finally, the high-maltose syrup was produced via the enzymatic hydrolysis of extruded-puffed cereals at high substrate concentrations (20 %). After hydrolysis for 180 min at an enzyme substrate ratio (E/S ratio) of 0.2, the syrup with dextrose equivalent (DE) value of 63, 62, and 61 were obtained from extruded-puffed brown rice, corn, and buckwheat, respectively. Our results showed the potential of using extruded-puffed cereals for producing high-maltose syrup.

Texture, sensory properties and functionality of extruded snacks from pulses and pseudocereal proteins

BACKGROUND

The protein-rich fractions of pulses and pseudocereals exhibit a well-balanced amino acid profile, particularly when combined in different portions, and are therefore high-value ingredients for the production of extruded snacks. However, the impact of a combination of pulses and pseudocereals on the physical and sensory qualities of extruded snacks has not been investigated up to now. Native or preconditioned protein isolates and concentrates from pulses - as single ingredients or in combination with protein-rich flours of pseudocereals - were analyzed regarding their thermal and functional properties in relation to extrusion characteristics. Low moisture extrusion cooking was used to investigate the impact of protein source (lentil, lupin, faba bean), pseudocereal source (quinoa, amaranth, buckwheat) and protein content (30%, 50%, 70%) on sectional expansion, specific hardness, density and sensory properties of the snacks.

RESULTS

With increasing protein content from 30% to 50%, the sectional expansion decreased and the density and specific hardness of the extrudates increased, which could be counteracted by preconditioning of the protein-rich ingredients. Lupin protein-based extrudates exhibited satisfactory texture and sensory properties. Extruded mixtures of pulses and pseudocereals (70% protein) exhibited a smaller sectional expansion compared to pulses as single ingredients (30%, 50%), regardless of pseudocereal type. However, the texture and sensory properties of the extruded blends were satisfactory.

CONCLUSIONS

We show for the first time that protein-rich fractions of pulses and pseudocereals can be processed into expanded snacks with favorable texture and nutritional properties such as increased protein contents (70%) and balanced amino acid profiles. © 2020 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Development of a Novel Rice-Based Snack Enriched with Chicory Root: Physicochemical and Sensory Properties

A novel rice-based snack enriched with chicory root flour (CRF) was developed by twin-screw extrusion. Chicory (Cichorium intybus L.) is one of the promising medicinal plants for the development of innovative food and may be considered a functional food ingredient. Central composite design (CCD) was employed to generate snack formulations by varying feed moisture (M, 16.3–22.5%), screw speed (SS, 500–900 rpm) and CRF content (20–40%). The optimization according to artificial neural network modeling and a genetic algorithm was applied to define optimal process conditions (17.6% moisture, 820 rpm and 24.1% of CRF) for obtaining the product with the highest expansion (3.34), crispiness (3.22 × 10−3), volume (2040 m3), degree of gelatinization (69.70%) and good color properties. Bulk density (110.33 g/L), density (250 kg/m3), and hardness (98.74 N) resulted in low values for the optimal sample. The descriptive sensory analysis evaluated low hardness and bitterness, with high crispiness for the optimal extrudate. This study points to the possibility of a novel chicory enriched extrudate production with desirable physicochemical and sensory properties.

Principles and Guidelines for In-Line Viscometry in Cereal Extrusion

In the food industry, extrusion cooking finds numerous applications thanks to its high productivity and nutrient retention. More specifically, cereal extrusion, e.g., for savory snacks and breakfast products has an important market share. For such applications, rheology, which addresses viscous and elastic contributions, plays an important role in developing, optimizing, and controlling the extrusion manufacturing technique. In this context, conventional off-line rheometers are not ideal for providing data, as the goal is to replicate the exact thermomechanical history to which the food is subjected in the extrusion process. Hence, to achieve reliable analyses, in-line viscometers that have mostly been tested using oil-based polymers were introduced. Biopolymers (e.g., starch), however, are highly sensitive to both heat and mechanical degradation, and the viscometer design has to be adapted accordingly to produce an accurate measurement. Alongside a discussion of the different designs available, this review will address the most common methodologies for measuring the steady shear viscosity, extensional viscosity, and the first normal stress difference for food applications, providing researchers in the biopolymer and food engineering fields with a general introduction to this emerging topic.

The effect of chickpea flour and its addition levels on quality and in vitro starch digestibility of corn-rice-based gluten-free pasta

Development of gluten-free (GF) pasta with improved nutritional attributes is one of the main trends in the gluten-free pasta industry. Considerable interest lays in introducing legume-based ingredients into traditional corn/rice GF formulations. This work aims to fortify multi-cereal (corn-rice) GF pasta with chickpea to investigate how different chickpea addition levels affect its quality and in vitro starch digestibility. Chickpea significantly increased pasta protein and dietary fibre contents to a level that supports the "source" or "high" fibre/protein content claims. Chickpea addition induced darkening, softening, adhesiveness decrease and solid loss reduction compared to the control. In addition, chickpea substitution significantly modified the in vitro starch digestion, which showed increasing resistant starch and decreasing slowly digestible starch contents suggesting potential mitigation of postprandial glucose response in vivo. Reformulating GF pasta with chickpea flour should, therefore, be considered as an effective tool to improve the corn-rice-based GF products' nutritional profile.

Impact of tomato pomace powder added to extruded snacks on the in vitro gastrointestinal behaviour and stability of bioactive compounds

In this study, extruded snacks enriched with tomato pomace powder (TPP) at ratios of 5, 10, 15, and 20% (w/w) were prepared based on some preliminary experiments. The effect of tomato pomace addition to extruded snacks on the total phenolic content, total antioxidant capacity, contents of lycopene and phenolics, as well as their in vitro bioaccessibility; and additionally, physical, textural and sensory properties of the samples were investigated. According to the results, increasing levels of TPP in snacks significantly increased the content of individual phenolics including gallic acid, protocatechuic acid, 2,5-dihydroxybenzoic acid, chlorogenic acid, rutin and quercetin. Similarly, increased amount of TPP in snacks enhanced the bioaccessible protocatechuic acid, chlorogenic acid, rutin and quercetin as well as lycopene (p < 0.05). TPP incorporated snacks displayed lower expansion indices, water absorption index (WAI) and water solubility index (WSI) and lightness; but had higher hardness, redness and yellowness values than the control. However, snacks had acceptable physical and sensory properties when enriched with 10% of TPP. The results suggest that tomato pomace can be added as a functional ingredient to improve the nutritional value of snack products.

Effect of Extrusion Temperature and Feed Moisture Content on the Microstructural Properties of Rice-Flour Pellets and Their Impact on the Expanded Product

Extrusion can lead to an expanded product or to a slightly expanded pellet, known as a third-generation (3G) snack. In this case, expansion occurs subsequently, in an independent thermal device (e.g., oven), out of the extruded pellet. During both processes, several structural changes occur which are linked to processing conditions, including cooking temperature, screw speed, formulation, and initial moisture content. However, a clear relationship between processing variables and the structure of pellets and expanded products has not yet been identified. Accordingly, this work aimed to study the effect of extrusion temperature (110, 135, and 150 °C) and moisture content (27, 29, and 31%) in rice-flour pellets and their microwave expansion, through a microstructural approach using micro-CT. The results showed that the lowest moisture content (27%) and the highest extrusion temperature (150 °C) led to the highest pellet volume and the highest wall thickness, which in turn led to the highest expansion after microwave heating (50 s, 800 W). Interestingly, no significant differences were observed when analyzing the ratio between the volume of the expanded products and the volume of the pellet (~2.4) when using the different processing conditions.

Development of Cellular High-Protein Foods: Third-Generation Yellow Pea and Red Lentil Puffed Snacks

This study aimed to evaluate how extrusion cooking conditions and microwave heating play a role in enhancing physical and thermal properties of third-generation expanded cellular snacks made from yellow pea (YP) and red lentil (RL) flours for the first time. Increasing temperature and moisture content during extrusion resulted in darker, crunchier and crispier products with higher expansion index (EI). Microwave heating after extrusion led to an increase in cell size and porosity of YP and RL products when qualitatively compared to extrusion alone. Additionally, extrusion followed by microwave heating resulted in extensive damage to starch granular structure and complete denaturation of proteins. Using microwave heating, as a fast and inexpensive process, following partial cooking with extrusion was demonstrated to greatly improve the physical and thermal properties of YP and RL snacks. Microwave heating following mild extrusion, instead of severe extrusion cooking alone, can potentially benefit the development of high quality nutritionally-dense expanded cellular snacks made from pulse flours.

Production of Extrudate Food with Mango By-Products (Mangifera indica): Analysis of Physical, Chemical, and Sensorial Properties

The novelty of this work is the use of two mango by-products, mango peel and kernel, to obtain an extruded food. As well as the development of this food through a design of mixtures, we conducted sensorial analysis of the food through a hedonic test, in order not only to develop an extruded food with mango by-products, but also to develop a food that will be accepted by the consumer. A simple lattice mixture design was carried out with 14 mixtures, where the components were white corn flour (WCF), mango peel flour (MPF) and mango kernel flour (MKF), both from the Tommy Atkins mango variety. Physical and chemical properties such as the expansion index (EI), hardness, water absorption index (WAI), water solubility index (WSI), total phenols, DPPH and ABTS were evaluated. An optimization region was found that included 3 design points. Mixtures 1, 6 and 12 were evaluated using a nine-point hedonic scale to determine the acceptability of the product. Appearance, taste, and texture of the extrudates was evaluated. The extrudate with the best overall acceptability and the optimum physical and chemical properties contained 58.33% white corn flour, 33.33% mango peel flour and 8.33% mango kernel flour.

Effects of soy flour types and extrusion-cooking conditions on physicochemical, microstructural and sensory characteristics of puffed rice snack base

The physicochemical properties of puffed rice snack base (PRSB) prepared via extrusion cooking under various feed moisture contents and screw speeds were investigated. The moisture content, screw speed, and soy flour type significantly (p < 0.05) affected the physicochemical properties of PRSB viz; size, density, porosity, color, breaking strength, crystallinity, water absorption index (WAI) and water solubility index (WSI). While, a slight effect on pasting properties was observed between PRSB added with defatted and full-fat soy flour, respectively. Soy flour lipids significantly (p < 0.05) influenced extrusion cooking conditions especially at high screw speed and feed moisture content. The result revealed that extrusion cooking with addition of full-fatty soy flour can be exploited as a viable method to produce PRS with a high expansion ratio and low breaking strength at recommended extrusion conditions of feed moisture content of 19 % and screw speed of 300 rpm.

A review: nutrition and process attributes of corn in pet foods

Corn is one of the largest cereal crops worldwide and plays an important role in the U.S. economy. The pet food market is growing every year, and although corn is well utilized by dogs, some marketing claims have attributed a negative image to this cereal. Thus, the objective of this work was to review the literature regarding corn and its co-products, as well as describe the processing of these ingredients as they pertain to pet foods. Corn is well digested by both dogs and cats and provides nutrients. The processing of corn generates co-products such as corn gluten meal and distillers dried grains with solubles that retain quality protein, and fibrous components that dilute dietary energy. Further, corn has much functionality in extrusion processing. It may yield resistant starch under certain processing conditions, promoting colonic health. Carotenoids in corn may enhance immune support in companion animals if concentrated. Mycotoxin contamination in grains represent a health hazard but are well controlled by safety measures. Genetically modified (GM) corn is still controversial regarding its long-term potential for mutagenicity or carcinogenicity, thus more long-term studies are needed. In conclusion, the negative perception by some in the pet food market may not be warranted in pet foods using corn and its co-products.

Modelling Volume Change and Deformation in Food Products/Processes: An Overview

Volume change and large deformation occur in different solid and semi-solid foods during processing, e.g., shrinkage of fruits and vegetables during drying and of meat during cooking, swelling of grains during hydration, and expansion of dough during baking and of snacks during extrusion and puffing. In addition, food is broken down during oral processing. Such phenomena are the result of complex and dynamic relationships between composition and structure of foods, and driving forces established by processes and operating conditions. In particular, water plays a key role as plasticizer, strongly influencing the state of amorphous materials via the glass transition and, thus, their mechanical properties. Therefore, it is important to improve the understanding about these complex phenomena and to develop useful prediction tools. For this aim, different modelling approaches have been applied in the food engineering field. The objective of this article is to provide a general (non-systematic) review of recent (2005-2021) and relevant works regarding the modelling and simulation of volume change and large deformation in various food products/processes. Empirical- and physics-based models are considered, as well as different driving forces for deformation, in order to identify common bottlenecks and challenges in food engineering applications.

Impact of Rapeseed Press Cake on the Rheological Properties and Expansion Dynamics of Extruded Maize Starch

Rapeseed press cake (RPC), an oil pressing side product rich in protein and fiber, can be combined with starch and valorized into directly expanded products using extrusion technology. The mechanism of starch expansion has been studied in detail, but the impact of RPC on expansion behavior is poorly understood. However, it can be linked to rheological and physicochemical properties and is a key product quality parameter. Blends with different amounts of RPC (0, 10, 40 g/100 g) were extruded at different barrel temperatures (100, 120, 140 °C) and moisture contents (24 or 29 g/100 g). The initial, intermediate and final sectional, longitudinal and volumetric expansion indices (SEI, LEI, VEI) were monitored directly, 10 s and 24 h after die exit to measure extrudate growth and shrinkage. The viscous and elastic properties of the extruded blends were investigated in a closed cavity rheometer. Starch and blends with 10 g/100 g RPC achieved a high initial SEI followed by significant short-term shrinkage. Blends containing 40 g/100 g RPC did not show any initial expansion. With increasing RPC content, the intermediate SEI decreased, but all samples reached a similar final SEI due to time-dependent swelling of the RPC blends. With increasing RPC content, the elasticity of the starch-based extruded samples significantly increased. Our study shows that comprehensive control and understanding of expansion mechanisms can be achieved only by investigating all stages of extrudate growth and shrinkage. We also found that the closed cavity rheometer is a powerful tool to correlate the rheological properties and expansion mechanisms of biopolymers.

Considerations for improvising fortified extruded rice products

Micronutrient fortification of rice by extrusion is an effective strategy to enhance micronutrient levels within rice-consuming individuals. The success of extrusion-based fortification is associated with micronutrient retention, enhanced bioavailability, low postprocessing losses, prolonged storage stability, and minimal sensory changes. The success of an optimally fortified product is primarily reliant upon the compositional considerations, but many attributes of extrudates can be indebted to the processing parameters too. Hence, an exhaustive investigation of this technology has been taken-up here, emphasizing on the compositional parameters in association with process parameters, which influence the final quality attributes like nutrient stability, bioavailability, and sensory properties. Based on these attributes of the end product, a collected data have been presented here to bring out the optimal compositional requirements. These together with cooking processes, extrusion process parameters, and storage conditions will enable formulate a product with enhanced sensory acceptance, better retention during cooking and storage, improved texture, and acceptable color. This review will thus help to optimize a need-based product, its quality, and enhance benefits of fortified extruded rice products.

Optimisation of the Extrusion Process through a Response Surface Methodology for Improvement of the Physical Properties and Nutritional Components of Whole Black-Grained Wheat Flour

Chronic undernourishment affects billions of people. The development of whole-grain food with high nutritional quality may provide a valuable solution to nutritional security. Black-grained wheat (BGW), as a rich source of protein and micronutrients, is a good raw material for value-added products. The objectives of this study were to investigate the effects of barrel temperature, feed moisture content, and feed rate on the physical properties and nutritional components of whole BGW flour extrudates and to optimise their processing conditions by using the response surface methodology. The increasing barrel temperature, feed moisture content, and feed rate affected the specific volume, expansion ratio, hardness, fracturability, water absorption index (WAI), water solubility index (WSI), and total starch content of the extrudates, but did not significantly affect the content of protein, ash, iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn). The extruded wheat flour had a significantly higher content of Fe and Cu, and a lower total starch content than the unextruded flour under extrusion conditions. A significantly higher content of protein, ash, Zn, Cu, and Mn, and a significantly lower total starch content were found in the extruded and unextruded flours made of whole BGW than in those made of whole white-grained wheat. According to the significance of the regression coefficients of the quadratic polynomial model, the optimum extrusion parameters were as follows: a barrel temperature of 145.63 °C, feed moisture content of 19.56%, and feed rate of 40.64 g·min-1 in terms of the maximum specific volume, expansion ratio, fracturability, WAI and WSI, and the minimum hardness. These results may be used by food manufacturers to successfully develop extruded products from whole BGW flour, meeting consumer demands and needs.

Utilization of Food Processing By-products in Extrusion Processing: A Review

The processing of agricultural products into value-added food products yields numerous by-products or waste streams such as pomace (fruit and vegetable processing), hull/bran (grain milling), meal/cake (oil extraction), bagasse (sugar processing), brewer's spent grain (brewing), cottonseed meal (cotton processing), among others. In the past, significant work in exploring the possibility of the utilization of these by-products has been performed. Most by-products are highly nutritious and can be excellent low-cost sources of dietary fiber, proteins, and bioactive compounds such as polyphenols, antioxidants, and vitamins. The amount of energy utilized for the disposal of these materials is far less than the energy required for the purification of these materials for valorization. Thus, in many cases, these materials go to waste or landfill. Studies have been conducted to incorporate the by-products into different foods in order to promote their utilization and tackle their environmental impacts. Extrusion processing can be an excellent avenue for the utilization of these by-products in foods. Extrusion is a widely used thermo-mechanical process due to its versatility, flexibility, high production rate, low cost, and energy efficiency. Extruded products such as direct-expanded products, breakfast cereals, and pasta have been developed by researchers using agricultural by-products. The different by-products have a wide range of characteristics in terms of chemical composition and functional properties, affecting the final products in extrusion processing. For the practical applications of these by-products in extrusion, it is crucial to understand their impacts on the qualities of raw material blends and extruded products. This review summarizes the general differences in the properties of food by-products from different sources (proximate compositions, physicochemical properties, and functional properties) and how these properties and the extrusion processing conditions influence the product characteristics. The discussion of the by-product properties and their impacts on the extrudates and their nutritional profile can be useful for food manufacturers and researchers to expand their applications. The gaps in the literature have been highlighted for further research and better utilization of by-products with extrusion processing.

Rheology of carbohydrate blends close to the glass transition: Temperature and water content dependence of the viscosity in relation to fragility and strength

Several modifications of the Williams-Landel-Ferry (WLF) equation that incorporate the water-content dependence of the viscosity are introduced and applied to the fitting the zero-shear viscosity of a systematic series of maltopolymer-maltose blends for water contents w between 4% and 70% (M. Dupas-Langlet et al., Carbohydrate Polymers 213 (2019) 147-158). These models include a previously published model that addresses the water-content dependence of the viscosity via a Gordon-Taylor-type modification of the C₂ coefficient of the WLF equation. New models that are based on two simple assumptions are introduced: 1. The viscosity at the glass transition temperature T_g decreases exponentially with the water content and 2. The WLF coefficient C₂ depends linearly on the water content. The modified WLF models allow to extract the so-called isoviscosity lines, that connect points of varying temperature and water content that are characterized by the same viscosity. Based on data obtained between T = -15 °C and 70 °C using shear rheology (w = 30-70% w/w) and dynamic mechanical thermal analysis (w = 4-9% w/w), we conclude that the models provide a good fit of the experimental data, and that additional data, specifically very close to the glass transition line, is needed, to assess the hypotheses underlying the various modified WLF models. It is established that the viscosity at T_g is dependent on the composition and decreases with the content of maltose and water. The modified WLF models are used to determine Angell's fragility parameter m and Roos' strength parameter S. m and S are observed to increase, respectively decrease with increasing water and maltose content, signifying an increasing temperature dependence of the viscosity close to T_g with decreasing diluent content. The application of the isoviscosity concept to unit operations in the food and pharmaceutical industry is discussed. Specifically, we show how to analyze atomization, agglomeration, sintering and compaction using the isoviscosity concept.

Berrios J. Tiger Nut (Cyperus esculentus) as a Functional Ingredient in Gluten-Free Extruded Snacks

Tiger nut (TN) is a nutritious source of gluten-free flour, used generally in healthy beverages, but its incorporation in gluten-free extruded snacks has not been explored. TN flour was blended at different concentrations (up to 70%) with rice flour and soluble fiber, for the development of gluten-free snacks on a twin-screw extruder. The effect of TN inclusion in the formulations was evaluated on relevant physiochemical characteristics of the snacks. Viscoamylograph of the raw formulations showed that TN addition increased (p < 0.01) onset temperature and delayed peak viscosity. In the extruded flours, TN contributed to limit the starch degradation during extrusion. Diameter, expansion ratio, true density, and total pore volume of the extrudates were reduced (pf < 0.01) by the increased TN content in the formulations, while bulk density rose. The surfaces of the extruded snacks were modified by the increasing inclusion of TN in substitution of rice in the formulations. Extrudates containing 10% TN showed the best overall texture profile. Moreover, TN addition enhanced the ash and protein content of the snacks and increased their total antioxidant activity. This study demonstrated that incorporation of 10% TN flour into rice-based formulation was suitable for making gluten-free snacks with acceptable physical properties.