Avocado by-products: Nutritional and functional properties

BackgroundAvocado (Persea americana Mill.) is a tropical and subtropical fruit that is native to Mexico and Central America; avocado is gaining increasing worldwide acceptance and has received extensive marketing and a wide distribution due to its relevant nutritional benefits for human health. Mexico harvests more than 30% of avocados worldwide, representing the main producer and exporter of avocado, which has become a crop of high interest and has great economic impact on Mexico.Scope and approachIn this paper, we describe relevant information on the production, composition and application of avocado, with an emphasis on its by-products, focusing on the proper use of waste and the possibility of monetizing waste for nutritional and environmental purposes. The entire avocado is rich in biocompounds (pulp, seed and peel) and has many health benefits, such as antimicrobial, antioxidant and anticancer activities, as well as dermatological uses and others. In this paper, we demonstrate the current panorama of production, exportation and uses of avocado in Mexico.Key findings and conclusionsSeveral food grade ingredients can be obtained from avocado wastes, particularly premium-grade fats or extracts with a high functional power. Studies should continue to identify the profiles and phytochemicals available to the business sector, which can also be implemented to valorize the nutritional and functional potential of avocado seeds and peels.     

绿茶粉粒径对小麦粉面团流变学特性的影响

绿茶粉内含物丰富,不同粒径的绿茶粉添加到小麦粉中对面团流变学特性的影响不同。本文制备3种粒度的绿茶粉,添加到小麦粉中,利用粉质仪、拉伸仪和面筋仪测定面团的流变学特性。研究结果表明,随着绿茶粉粒径的减小,面团吸水率、形成时间及稳定时间均显著增大,面团经过一定时间的醒发后,粒径为20μm的绿茶粉拉伸曲线面积、拉伸比例最大,不同粒径的绿茶粉面团拉伸阻力R50及延伸度变化不大;绿茶粉粒径越小,面团的抗扭力增加,面筋强度增强;综合可以看出绿茶粉的添加有利于改善小麦粉面团的面筋网络结构,优化其加工性能。     

Characterization of bread dough: Rheological properties and microstructure

The change in rheological and microstructural properties of wheat flour dough as a function of water and yeast content, and with addition of hydrocolloids is described. The rheological properties vary with the size of the bubbles and measurements were made on controlled shear/stress rheometer. Confocal laser scanning microscope (CLSM), accompanied with image analysis technique, was used to obtain microstructure of the dough. It was found that with an increase in water content the moduli values decreased and the mean bubble diameter increased. As concentration of yeast increased, the bubbles became smaller and the moduli values increased. Addition of hydrocolloids like sodium alginate and xanthan gum led to increased moduli values and generally caused the bubbles in the dough to shift towards narrower distributions. An inverse relation between bubble size and storage modulus is found.     

Relationship of polymeric proteins and empirical dough rheology with dynamic rheology of dough and gluten from different wheat varieties

Dynamic rheological properties of dough and gluten were studied and related to the empirical rheology (Farinograph) and the protein fractions of different wheat varieties. The relationship between high molecular weight-glutenin subunits (HMW-GS) and dough strength was evaluated. Dynamic rheology of under-, optimum- and over-mixed dough was also related to the farinograph characteristics and the protein fractions. The moduli (G′ and G″) of over- and optimally-mixed dough were significantly correlated with Farinograph characteristics and SDS-unextractable polymeric protein (UPP) content. The temperature-induced rheology of glutens revealed that the differences in G′ and G″ during heating as well as cooling were related to the UPP content. Principal component analysis revealed wide range of differences in the dynamic rheology among the wheat varieties mainly attributed to UPP.     

Functional response of diluted dough matrixes in high-fibre systems: A viscometric and rheological approach

Hydrocolloids (carboxymethylcellulose, locust bean gum, high ester pectin) and prebiotic oligosaccharides (inuline and gluco-oligosaccharides), singly and in hydrocolloid/oligosaccharide binary blends were tested at different level of fibre replacement (from 0% up to 12%) to investigate the impact of dietary fibres on bread dough linear and non linear rheological performance. Incorporation of locust bean and carboxymethylcellulose at a replacement higher than 6% into bread doughs led highly reinforced hydrated flour-fibre blends with promoted values for storage and loss moduli, hardness, and pasting/gelling features; whereas pectin and pectin blends systems at any substitution level were the softer and stickier. Obtained results on rheological performance strongly endorse the viability of locust bean and carboxymethylcellulose blended with prebiotic oligosaccharides, to replace wheat flour at medium-high substitution level to serve either as sources of dietary fibre for the production of healthy baked goods or as thickening and structuring agents for baking industry.     

Relationship of polymeric proteins with pasting,gel dynamic- and dough empirical-rheology in different Indian wheat varieties

The protein characteristics of flours from fifteen Indian wheat varieties were studied and related to pasting, gel viscoelasticity and dough properties. The analysis of polymeric proteins showed glutenins, gliadin and glutenin to gliadin ratio ranged between 28.14 and 40.44%, 45.33 and 55.83% and 0.50 and 0.89, respectively. Paste breakdown was low in flours with higher protein content. Viscoelastic properties of flour gels from different varieties showed significant variation and were dependent more on protein than amylose content. The gelation behavior of cooked pastes measured during cooling and holding at 10 °C was explained by an equation. Dynamic moduli of gels were positively correlated with total protein content and negatively correlated to the percentage of unextractable polymeric protein (UPP). Dough strength was positively related to UPP and glutenin content.     

Extrusion processing of raw food materials and by-products: A review

ABSTRACT

Extrusion technology has rapidly transformed the food industry with its numerous advantages over other processing methods. It offers a platform for processing different products from various food groups by modifying minor or major ingredients and processing conditions. Although cereals occupy a large portion of the extruded foods market, several other types of raw materials have been used. Extrusion processing of various food groups, including cereals and pseudo cereals, roots and tubers, pulses and oilseeds, fruits and vegetables, and animal products, as well as structural and nutritional changes in these food matrices are reviewed. Value addition by extrusion to food processing wastes and by-products from fruits and vegetables, dairy, meat and seafood, cereals and residues from starch, syrup and alcohol production, and oilseed processing are also discussed. Extrusion presents an economical technology for incorporating food processing residues and by-products back into the food stream. In contemporary scenarios, rising demand for extruded products with functional ingredients, attributed to evolving lifestyles and preferences, have led to innovations in the form, texture, color and content of extruded products. Information presented in this review would be of importance to processors and researchers as they seek to enhance nutritional quality and delivery of extruded products.     

Rheological properties of rice pasta dough supplemented with proteins and gums

Rheological properties of rice pasta dough were studied by creep-recovery tests for various formulations containing guar gum (0.5%), casein (1%), and egg white (1%) mixtures. Non-gelatinized rice semolina (RS) was also mixed with gelatinized RS in different ratios (0, 25, 50, 75 and 100%) for each formulation. The effects of gelatinization, gum and proteins on pasta dough rheology were determined by a control stress rheometer (Haake Rheostress 1). From the creep-recovery data it was obvious that as the amount of gelatinized fraction increased there was an increase in the elasticity of the samples. However, the samples that were produced with 75 and 100% gelatinized RS in the formulation were not smooth in texture, but lumpy. From the creep-recovery and dynamic oscillation measurements it was found that guar gum and protein mixture can be used as a stabilizer together with 50% pre-gelatinized rice semolina. This will result in an improvement in dough properties during gluten free pasta processing from rice.     

Rheological and colour properties of apple jellies supplemented with inulin with various degrees of polymerisation

The objective of this study was to analyse the influence of inulin with different degrees of polymerisation (DP values) and oligofructose preparation on physicochemical and rheological properties of apple jelly. It has been determined that both the addition of inulin (independently of DP) and oligofructose significantly modify the rheological and textural properties of the analysed desserts. Preparation with high DP results in increased moduli, preparation with moderate levels results in their decrease, while preparation with low DP levels initially decreases and then increases the values of both moduli. Similar tendencies are exhibited by the remaining parameters of rheological characteristics. Supplementation with inulin and oligofructose influences, but not as markedly, physicochemical properties. It has been observed that the manner in which water is bound by the applied preparations may have a significant impact on the properties of jelly. In the majority of cases, the variability of the parameters, for which statistically significant differences have been determined, depended on the type and level of the additive, and this impact varied between individual preparation types. The study conducted has enabled the conclusion that inulin may pose an attractive ingredient in desserts with health-promoting properties.     

Influence of modified starches on properties of gluten-free dough and bread. Part I: Rheological and thermal properties of gluten-free dough

The aim of this study was to analyze the influence of chemically modified starches (HDP and ADA) and high amylose corn starch (HACS) on the rheological and thermal properties of gluten-free dough based on corn and potato starches with pectin and guar gum. The results indicate that the dough with the addition of modified starch behaves as weak gel, the value of storage modulus G′ significantly depends on the frequency and the values of tan δ = G″/G′ range from 0.32 to 0.49. Significant influence of hydroxypropylated distarch phosphate (HDP) on the viscoelastic properties of dough was observed. The share of modified starch in the system caused a decrease of the instantaneous and viscoelastic compliance. It also influenced the retardation time and zero shear viscosity. The application of modified starches (HDP and ADA) for dough preparation did not have much impact on the pasting characteristics. However, significant reduction of the onset and end viscosities were found for high amylose starch (HACS). Thermograms obtained for individual dough systems were characterized by the presence of two peaks, associated with the existence of two different starches in the system. No significant effect of modified starch on the onset temperature (T_O) and only a slight effect of HACS starch on gelatinization enthalpy were observed. However, the level of addition of individual starch affected peak and end (T_E) temperatures, depending on the type of preparation.     

Improvers and functional ingredients in whole wheat bread: A review of their effects on dough properties and bread quality

BackgroundDespite the associated health benefits of whole grains, consumption of whole grain products remains far below recommended levels. Whole wheat bread is often associated with many distinctive attributes such as low loaf volume, firm and gritty texture, dark and rough crust and crumb appearance, bitter flavor, and reduced shelf-life. There is a need to improve its quality and sensory characteristics so as to increase consumer appeal and, ultimately, increase the intake of whole wheat bread. The inclusion of various ingredients improves dough and bread properties.Scope and approachThis review examines the effects of enzymes, emulsifiers, hydrocolloids, and oxidants on the properties of whole wheat bread and dough, with particular attention to effects on loaf volume and hardness. Wheat gluten and other plant materials are also discussed. Gaps in the research into whole wheat bread are identified, and future research needs are recommended.Key findings and conclusionsXylanase reduces the water absorption of whole wheat flour and increases loaf volume and crumb softness by hydrolyzing ararbinoxylans. α-amylase can be beneficial under certain conditions. Phytase may activate endogenous α-amylase. G4-amylase is promising but needs validation by further research on its effect on loaf volume, crumb hardness, and staling. Vital wheat gluten overcomes many of the challenges of whole wheat bread production and is found in the majority of commercial whole wheat breads. Emulsifiers DATEM and SSL can improve the volume, texture and staling profile of whole wheat bread. Several types of improvers are generally needed in combination to provide the greatest improvement to whole wheat dough and bread.     

Physico‐chemical and functional properties of starch isolated from ginger spent

Studies were carried out on starch isolated from ginger spent, obtained after the extraction of oleoresin, to explore the possibility of its use as a food ingredient. AM content was found to be 25.5%. SEM showed the granules were disc‐shaped as well as ovoid with a smooth surface. The average granule size was 22.5 ± 3.5 µ in length and 16.9 ± 4.8 µ in width with thickness of ∼3 µ. Ginger spent starch exhibited a high gelatinization temperature (88°C), peak viscosity (678 Brabender units (BU)) and cold paste viscosity (777 BU). It also possessed low paste clarity and higher freeze–thaw stability. Dynamic rheological properties of ginger spent flour, measured using parallel plate geometry showed that the storage modulus (G′) increased and loss modulus (G″) decreased as a function of frequency. Starch from ginger spent flour with high gelatinization temperature and low in vitro starch digestibility (45%) is suitable to use for development of speciality food formulations.     

Prediction of the rheological properties of wheat dough by starch-gluten model dough systems: effect of gluten fraction and starch variety

The present study sought to investigate the rheological properties of wheat starch-gluten (WS-G) and potato starch-gluten (PS-G) model doughs with different gluten fractions to elucidate the effectiveness of using model dough to predict wheat dough properties. The highest linear viscoelastic region, frequency dependence, maximum creep compliance and the lowest viscoelastic modulus and zero shear viscosity were observed in the wheat dough, followed by WS-G and PS-G model doughs. PS exerted a more significant damage effect on the gluten network while WS shared a tight integration with gluten protein, forming a more stable dough structure. The viscoelasticity of the model doughs shared a close association with the wheat dough under increased gluten fraction, while the frequency dependence of the model doughs showed no trend towards wheat dough. Therefore, starch-gluten model dough could not fully stimulate the functionality of wheat dough irrespective of its gluten fraction.     

Phenolic and antioxidant composition of by-products from the cider industry: Apple pomace

Eleven different cider apple pomaces (six single-cultivar and five from the cider-making industry) have been analysed for low molecular phenolic profiles and antioxidant capacity. The Folin index ranged between 2.3 and 15.1 g gallic acid per kg of dry matter. Major phenols were flavanols, dihydrochalcones (phloridzin and phloretin-2′-xyloglucoside), flavonols and cinnamic acids (chlorogenic and caffeic acids). The group of single-cultivar pomaces had higher contents of chlorogenic acid, (-)-epicatechin, procyanidin B2 and dihydrochalcones, whereas the industrial samples presented higher amounts of up to four unknown compounds, with absorption maxima between 256 and 284 nm. The antioxidant capacity of apple pomace, as determined by the DPPH and FRAP assays, was between 4.4 and 16.0 g ascorbic acid per kg of dry matter, thus confirming that apple pomace is a valuable source of antioxidants. PLSR analysis gave reliable mathematical models which allowed to predict the antioxidant activity of apple pomace as a function of the phenolic profile. The variables with the higher modelling power were phloridzin > procyanidin B2 > rutin + isoquercitrin > protocatechuic acid > hyperin.     

Effect of chemical composition of wheat flour and functional properties of dough on the quality of south Indian parotta

Six flours differing in quality were analysed for their chemical and rheological parameters. South Indian parottas were prepared and evaluated for their textural characteristics using an Instron universal testing machine (UTM) and their sensory characteristics by a trained panel. The correlation coefficient data indicated that among the chemical characteristics of flours, dry gluten, protein and SDS sedimentation value were found to be the best indices in predicting the quality of parotta. The rheological characteristics, such as farinograph water absorption, extensograph ratio figure and area, and Instron apparent biaxial extensional viscosity (ABEV), hardness and cohesiveness were found to be highly correlated to the overall quality score of parotta. Sensory texture of parotta was found to be highly correlated to shear force as well as compression force (r=0.99, P ≤ 0.001) indicating that shear and compression forces could be considered as the best indices of sensory texture of parotta.     

Effect of sterilisation on dietary fibre and physicochemical properties of onion by-products

Food industries are forced to develop productions without secondary residues. Therefore, there is a considerable emphasis on the recovery, recycling and upgrading of wastes. The possibility has been suggested for the conversion of onion waste into food ingredients, but with a stabilisation treatment being necessary. The objective of this work was to study the effect of sterilisation on fibre fractions, fibre composition and physicochemical properties of onion by-products to evaluate the use of sterilised onion by-products as a source of fibre.     

Microbial, physical and sensory properties of yogurt supplemented with lentil flour

In this study, skim milk (9.5% w/v solid content) was supplemented with 1-3% (w/v) lentil flour or skim milk powder, inoculated with a yogurt culture, fermented and stored at 4 °C. Acid production during the fermentation, microbial growth, physical properties (pH, syneresis, and color), rheological properties (dynamic oscillation temperature sweep test at 4-50 °C), during 28 days of refrigerated storage and also sensory properties (flavor, mouth feel, overall acceptance and color) after production, were studied. Milk supplementation with 1-3% lentil flour enhanced acid production during fermentation, but the microbial population (CFU) of both S. thermophilus and L. delbrueckii subsp. bulgaricus were in the same range in all lentil flour and skim milk powder supplemented yogurts. The average pH of samples decreased from 4.5 to 4.1 after 28 days storage. Syneresis in 1-2% lentil flour supplemented yogurts was significantly higher than all other samples; however, greater lentil supplementation (3%) resulted in the lowest syneresis during the 28 days storage. With respect to color, “a” and “L” values did not significantly differ in all samples and remained constant after 28 days whereas “b” value increased as a result of lentil supplementation. Yogurt with 3% lentil flour showed higher storage (G') and loss (G?) moduli in comparison with samples supplemented with 1-3% skim milk powder and the non-supplemented control yogurt. Storage modulus (G') was higher than loss modulus (G?) in all samples and at all temperatures between 4 and 50 °C and they showed a hysteresis loop over this temperature range when the samples were heated and cooled. 1-2% lentil flour supplemented yogurt showed comparable sensory properties in comparison with 1-2% skim milk powder supplemented yogurt and the control sample.     

制粉方式对燕麦粉理化及面团特性的影响

以坝莜1号燕麦籽粒为原料,分别制粉获得炒制燕麦粉、燕麦片磨粉、超微燕麦粉3种燕麦面粉,并以实验室粉碎获得燕麦粉为对照,系统比较了不同处理获得燕麦粉的出粉率、理化指标以及面团特性。表明:炒制燕麦粉、燕麦片磨粉、超微燕麦粉的出粉率分别为79.4%、85.0%及95.0%。与对照燕麦粉相比,3种处理燕麦粉的脂肪含量均增加,而蛋白质含量、β-葡聚糖含量和灰分含量均减小。超微燕麦粉破损淀粉含量高;燕麦片磨粉色泽L值和a值最高,炒制燕麦粉的b值最大。峰值黏度、DSC热焓值从高到低依次为燕麦片磨粉、炒制燕麦粉和超微燕麦粉,且差异显著(P0.05)。扫描电镜观察发现燕麦片磨粉淀粉颗粒保留完整。3种燕麦粉的吸水率、峰值黏度、回生值、稳定时间都差异显著(P0.05),其中,炒制燕麦粉和超微燕麦粉吸水率高。总体而言,炒制燕麦粉各项指标较优。