67 research outputs found

    Role of starch gelatinization and fragmentation in extruded flour functionality

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    El objetivo de esta tesis es el desarrollo de nuevos productos a base de plantas con mejor valor físico, organoléptico y/o nutricional utilizando harinas extruidas como ingrediente funcional. Se evaluó el efecto de aspectos tales como la fuente de almidón, el tamaño de partícula o la severidad del tratamiento de extrusión de las harinas. Las harinas extrusionadas se utilizaron para elaborar mahonesas y bizcochos reducidos en grasa aprovechando la gran capacidad de absorción-retención de agua en frío del almidón pregelatinizado. Aprovechando este poder espesante se elaboraron salsas instantáneas, sin calentamiento, y rebozados fritos con mayor crujiencia y mejor valoración organoléptica. A su vez, se estudió el efecto de la fragmentación durante la extrusión a la hora de reducir la dureza de los geles de almidón y, por tanto, de los fenómenos de endurecimiento/sinéresis. Por último, la fragmentación se aprovechó para aumentar el almidón lentamente digestible en panes sin gluten.Departamento de Ciencias AgroforestalesDoctorado en Ciencia e Ingeniería Agroalimentaria y de Biosistema

    Characterization of Starch by Vibrational Spectroscopy

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    To develop a dispersive Raman spectroscopic method for measuring amylose-amylopectin ratios of corn starch mixtures, 67 mixtures were prepared by randomly mixing waxy and normal corn starches. Amylose contents were measured using a dual wavelength iodine binding colorimetric method. Raman data were collected from 250 to 3200 cm-1 using optimized instrument parameters. Partial least-squares (PLS) and principal components regression (PCR) were used to prepare multivariate calibration models; however, PLS commonly outperformed PCR. Truncating the spectra to 250 to 2000 cm-1 improved the results (r2 of validation = 0.831, SEP = 2.90%). Removal of a cold water swelling starch from the data also offered a slight improvement in results (r2 of validation = 0.860, SEP = 2.70%). Dispersive Raman spectroscopy may not be well suited for quantifying amylose content of starch mixtures; however, the method was easily capable of discriminating between waxy and normal starches. This may allow the method to be used for confirming the identity of starch shipments. A dispersive Raman spectroscopic method for measuring retrogradation in corn starch gels was investigated. Thirty-six gels were prepared, stored at 4° C and measured at regular time intervals (0 h, 24 h, 48 h, 72 h, 120 h, 168 h after preparation). After each measurement, the gels were freeze-dried, then each resultant dried gel was ground into a powder and measured using X-ray diffraction. Relative crystallinity was determined, and intensity changes in the Raman band at 480 cm-1 were measured. No correlation was found between changes in the 480 cm-1 band and the relative crystallinity of the gels (r2 \u3c .1). The low starch concentration used may have caused the poor Raman signal strength and the unpredictable changes in the X-ray diffraction data. The experiment found that measuring retrogradation in very dilute starch gels could be problematic, and that more development is needed in order to apply Raman spectroscopy to in a food system like white pan bread. Advisor: Randy Wehlin

    Nutritional and functional improvement of gluten-free breads : addition of beta-glucans of different origins and molecular weights according to the health claims approved by the EFSA

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    Esta tesis doctoral aborda el enriquecimiento de pan sin gluten con (1->3)(1->4)-beta-glucano procedente de avena o cebada, en dosis conformes con las declaraciones de salud aprobadas por la EFSA. También explora el enriquecimiento con (1->3)(1->6)-beta-glucano procedente de levadura y hongos. Los resultados confirman la posibilidad del enriquecimiento del pan conservando una adecuada calidad física y nutricional. Los factores de estudio que han resultado determinantes son el origen del β-glucano, su concentración y su peso molecular. Para conseguir panes de calidad se ha concluido la necesidad de una optimización de la hidratación de la masa de pan en función de la concentración de fibra añadida y del empleo conjunto de HPMC de fuerza de gel débil. También se ha comprobado la conveniencia y viabilidad de la aplicación de un tratamiento térmico de la harina de arroz para destruir su actividad β-glucanásica y preservar el peso molecular del β-glucano en el producto final.Departamento de Ingeniería Agrícola y ForestalDoctorado en Ciencia e Ingeniería Agroalimentaria y de Biosistema

    Non-traditional grains in low and high moisture extrusion applications –residence time, physico-chemical properties and resistant starch

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    Master of ScienceDepartment of Grain Science and IndustrySajid AlaviSorghum, millets and teff are important staple crops worldwide, especially in semi-arid regions of Africa and India because of their drought tolerance. However, lack of research and other limitations have restricted their usage in food products. This study is focused on extrusion processing of low and high tannin sorghum varieties, millet and teff for high and low moisture applications, and to investigate process characteristics such as residence time distribution and specific mechanical energy, physico-chemical properties of resultant food products (such as pre-cooked pasta and expanded snacks) and their resistance starch content. Results from preliminary lab scale extrusion, including optimization of starch type and level for pre-cooked pasta and in-barrel moisture for expanded snacks, were used to design pilot-scale studies on a twin-screw extruder. In the first pilot-scale experiment, decorticated white sorghum blends prepared with addition of mono-glycerides (0.5%, 1% and1.5%) and salt (1%) were processed at three different in-barrel moisture contents 40%, 44% and 48% (wet basis) for processing of precooked pasta. The optimum formulation containing 1% mono-glycerides and process conditions corresponding to 48% in-barrel moisture were also used to develop precooked teff and millet pasta. The non-traditional grain based pastas were investigated for cooking quality, thermal characteristics using differential scanning calorimeter, pasting properties using rapid visco analyzer and texture profile analysis. In general, increasing in-barrel moisture led to reduction in solid losses (ranging from 4.0-8.2% for all treatments), indicating improvement in cooking quality. On the other hand, increase in mono-glycerides concertation led to higher cooking losses, and also affected pasting and textural properties significantly. Sorghum-based precooked pasta was of best quality while millet pasta was poorest in cooking quality, visual and textural attributes. Cooking loss for control pre-cooked pasta produced in this experiment using semolina was 4.5%, and commercial semolina pasta was 3.2%. Residence time distribution in pilot-scale twin screw extruder, during high moisture process conditions used for pre-cooked pasta, was also investigated at three different in-barrel moistures (40%, 44% and 48%) and monoglycerides/ lipid (0.5, 1% and 1.5%) concentrations. Increase in in-barrel moisture significantly decreased mean residence time. For example, mean residence time was 4.47 min at 40% moisture, 3.89 min at 44% and 3.74 min at 48%. On the contrary, residence time significantly increased with lipid level. For example, mean residence time was 3.87 min at 0.5% concentration of mono-glycerides, 4.48 min at 1% and 4.70 min 1.5%. In the second experiment focusing on low moisture applications, pilot-scale twin screw extrusion was used to process decorticated white sorghum and high tannin sumac sorghum for expanded snacks. The addition of sumac bran decreased the specific mechanical energy input (366-578 kJ/kg) and expansion ratio (6.4-7.9), and resulted in higher piece density of extrudates. Use of sumac bran and sumac flour led to increase in resistant starch content, although it was less than 1% for all treatments. Therefore, extrusion with ingredients having high tannin content does not provide value, despite tannins being associated with resistant starch at least in raw materials

    Characteristics and functional properties of green banana flour: An opportunity for functional bread production

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    The demand for functional food products has led to an increased interest in nutrients such as minerals, vitamins, bioactive compounds, fibre and prebiotics to be present in food formulations. Amongst the prebiotics, Resistant starch (RS) has gained more attention in recent years, due to its acknowledged health benefits such as prevention and control of colon cancer, diabetes, and obesity. Banana, the world’s most favourite fruit, is one of the richest sources of RS at early stages of ripeness, when it is green (unripe). According to some estimates, more than 100 billion bananas are consumed globally each year, with an annual per capita consumption of 20 kg. Green banana pulp is a rich source of essential phytonutrients, phenolic compounds, vitamin B group, ascorbic acid and tocopherols, while the green banana peel is a rich source of minerals, bioactive compounds and dietary fibre (DF) such as pectin, cellulose, hemicelluloses and lignin. Considering the nutritional value of both pulp and peel of green bananas, the production of green banana flour (GBF), which can be obtained by proper drying techniques, provides a way to preserve the nutritional benefits and increase the shelf-life of banana nutrients. White bread is the most popular bread type in the world, however, there is a growing research on fortifying bread with an array of different DF and functional compounds to take advantage of bread as a carrier of health benefiting compounds. Very few studies available that considered the effect of the GBF on technological properties, nutritional aspects and volatile fingerprint. The physicochemical and thermal properties of GBF obtained from air oven drying (ODF) at three temperatures (50, 80 and 110 °C) and freeze-drying (FDF) were compared to white wheat flour (WF). Lightness and yellowness were negatively affected by the oven temperature increment. The FDF samples exhibited higher a* and L* values and had the closest browning index to WF (P-value 0.05). While the ODF110 presented the highest pasting temperature (81.23 °C) and breakdown viscosity (7118.67 cp) amongst the GBF samples, ODF50 were the only heat-treated samples that showed similar hold, final and setback viscosity values to those found in the FDF. In terms of mineral contents, all GBF samples had higher concentrations of K, Mg, Ca and Zn compared to the WF which makes GBF as a better source of these nutrients (P-value 20% fortification level was observed. The ODF-fortified samples had higher browning index compared to control and FDF ones. The addition of both GBF types improved macro minerals (Mg, Ca, Na, K and P) without a significant change in micro minerals (Fe, Zn, and Mn). The use of FDF in bread resulted in a marked increase in both resistant and slow digestible starch content in F30 compared to ODF fortified samples at their comparable fortification levels. GC-MS-based chemical fingerprinting successfully detected more than 100 volatile compounds in the GBF fortified bread samples. Chemometrics methods used to compare the effect of GBF type in bread (FDF and ODF-fortified-bread), fortification level (10%, 20% and 30%) and bread part (crumb and crust) on the formation of volatile compounds. Furan (furfural, 2-furanmethanol), Strecker aldehydes (2- methyl butanal and 3-methylbutanal) and ketone (2-undecanone) were the most abundant volatiles in crust while alcohol (1-hexanol and 1-heptanol) and ester (ester butanoic acid ethyl) abundant in the breadcrumb. The level of fortification had a significant impact on the formation of 3-methyl-butanal (P-value < 0.05). Furthermore, bread made with freeze-dried GBF had more distinguished ‘banana-like’ flavour due to the presence of ethyl ester butanoic acid and 2-undecanone, while bread made with ODF represented more Maillard-related compounds which could signify a wood malty aroma impression. It can be concluded that fortification of bread with the GBF achieved from freeze drying had a more desirable results from technological and nutritional points of view. Although between 10% and 20% fortification level there was no clear difference, the 30% bread samples showed a high value nutritious bread with distinctive volatile flavour. Overall, the type of the drying method of GBF preparation had an impact on developing discriminant volatiles compared to bread part and fortification level

    Functional Cereal Foods for Health Benefits: Genetic and/or Processing Strategies to Enhance the Quali-Quantitative Composition of Bioactive Components

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    Cereal foods comprise a large variety of products that make up the main part of the diet of the world population. Despite decades of research to improve cereals and cereal food quality, worldwide research coordination is now required due to market needs, processing, and climate change. Cereals and cereal foods are an important source of energy (carbohydrates, proteins, and fat), and offer a range of non-nutrient bioactive components (i.e., vitamins, minerals, dietary fiber, and phytochemicals) that provide different grades of health benefits. The main challenges for the near future include the exploration, valorization, and improvement of genetic variation for nutrients and bioactive food components; the use and implementation of biotechnological, preprocessing, and processing strategies to improve content; and the evaluation of health properties for health claims

    Quality Evaluation of Plant-Derived Foods Ⅱ

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    Dear Colleagues, It is well established that preference (but not exclusivity) for plant-derived foods can result in both health and environmental benefits. However, it must be acknowledged that not all plant-derived foods present the same quality to consumers. Hence, traditional and novel tools to assure high-quality standards have to be applied to these types of foods. At the same time, the definition of quality may be different from product to product and must be studied accordingly. Hence, the contents of bioactive compounds, amount of fat or fatty acid profiles, vitamins, carbohydrates, volatile compounds, and microbial safety or sensorial characteristics are some of the parameters that can provide an insight into plant-derived food quality. Of course, this type of food is usually subject to some kind of postharvest processing or storage, which can alter their properties. This has also led to the need to study how these procedures change the characteristics of the original food. This Special Issue on “Quality Evaluation of Plant-Derived Foods Ⅱ” focuses on the topic of the quality assessment of plant-derived foods. This includes novel approaches to this line of research, but also the use of the established methodologies for novel plant foods, understudied species, or new data on known plant foods

    Effect of Combining Highly Digestible Protein and Waxy Starch Traits on Sorghum Endosperm Functionality and Protein Digestibility

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    Sorghum is known for its resilience to climate change and suitability to arid areas, having several potential health benefits such as controlling blood glucose and inflammation. However, functionality of sorghum as a food ingredient is limited due to the hydrophobic proteins. Sorghum mutant with a highly digestible (HD) protein (irregularly shaped) has potential for food application. The goal of this research was to establish the relationship between combined HD - waxy starch in hard endosperm sorghum on its functionality and protein digestibility. First, the suitability of the standard in vitro pepsin assay to identify the HD protein traits in hard endosperm sorghum was checked. The pepsin assay was not reliable in distinguishing the HD and regular low digestible (LD) protein as the digestibility was not consistent across locations and year. For the first time, field emission scanning electron microscope (FE-SEM) was effective to qualitatively identifying the HD protein body. The physicochemical properties of improved HD sorghum lines in waxy versus normal starch background were compared to the LD counterparts. HD-waxy combinations had better functionality in terms of water solubility (%) (7.10 versus 4.68 for normal LD), pasting properties (higher peak (more starch swelling) and lower final (slower retrogradation) viscosities), that indicated better interaction with water. The HD sorghum also had higher lysine content (2.15%) compared to the wild LD control (1.47% of total protein). Finally, the improved sorghum lines with the HD protein traits were tested in model foods in comparison with the LD ones and wheat controls. Pancake, cookie and bread were selected as model foods. The HD-normal gave pancakes with higher diameter (mm, 89.6 versus 87.5 for the LD normal) as well as higher moisture (% db, 45.2 versus 41.2 for the LD-normal) at 100% sorghum, most likely due to higher level of water absorption by the HD-protein. The same treatment also resulted in cookies of lower hardness (g, 1715 versus 4705 for the LD-normal). The HD sorghum resulted in denser bread crumb with faster firming, likely due to retained moisture migrating during storage (staling). The implication is that the improved HD-normal sorghum gave pancakes and cookies with desirable attributes making it an appealing ingredient in batter-based products as a partial substitute for wheat, or as gluten-free healthy grain with improved processing and nutritional qualities

    Brašno - Kruh '15

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    Proceedings contains 28 original research articles presented at 8th International Congress Flour – Bread ’15 and 10th Croatian Congress of Cereal Technologists Brašno – Kruh ’1
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