Effect of alkaline extraction on the structure of the protein of quinoa (Chenopodium quinoa Willd.) and its influence on film formation

It is important to produce hydrophobic edible protein films for use in foods. The aim of this study was to evaluate the effect of alkaline extraction of quinoa proteins (QP) on the structure and their film‐forming ability without plasticiser. QP were extracted between pH 8 to 12, and their structure was evaluated by PAGE‐SDS, size‐exclusion HPLC light scattering, fluorescence spectroscopy and SH and SS. Film was characterised by FTIR, SEM, tensile strength, barrier and colour. Structural changes of QP showing that alkalinisation over pH 10 produce significant denaturation/aggregation/dissociation structural changes in QP. pH 12 was the condition to form a film (film₁₂). FTIR showed hydrogen bonds and hydrophobic film interactions. Film₁₂ had 16.6 ± 3.8% elongation and 15.7 ± 1.1 MPa tensile strength, and water vapour permeability was 5.18 ± 0.38 g mm m^?2 day^?1 kPa^?1. Film₁₂ had a brownish colour. A high degree of denaturation/aggregation/dissociation of QP structure is required to form a film without plasticiser.     

Effect of Processing on the Physico-Chemical Characteristics of Quinoa Flour (Chenopodium quinoa,Willd)

The nature and extent of the modification of starch in quinoa, caused by various processes like cooking and autoclaving of the seeds, drum drying of the flour and extrusion of the grits was investigated by measuring the physico-chemical properties - the water absorption, water solubility, swelling power, viscosity and degree of gelatinisation - of the processed samples. Autoclaved samples showed the lowest degree of gelatinisation (32.5% by DSC) of the starch, while the degree of gelatinisation of the precooked/drum dried samples was found to be 97.4% by DSC method. Higher polymer degradation was observed in cooked samples than in autoclaved samples as seen in the gel chromatographic separation. The water solubility in cooked samples (5.44 to 15.58) and in autoclaved samples (7.02 to 9.64) increased with the process time. In the extrusion process, the moisture content as well as the compression ratio was found to affect the degree of starch modification significantly (p <0.01).     

藜麦发芽过程中蛋白质与皂苷及淀粉消化特性的变化规律

发芽是改善谷物质构及其营养价值的一种高效的加工方式。本文研究了藜麦发芽过程中蛋白质与皂苷及淀粉消化特性的变化规律。结果显示,发芽显著地提高了藜麦中粗蛋白和可溶性蛋白含量,分别增加了5.38%和17.55%。随着发芽时间不断增加,藜麦总淀粉、直链淀粉及支链淀粉含量分别减少25.95%、4.86%和29.53%,而还原糖含量增加了26.60%。发芽处理显著改善了藜麦种子的淀粉消化性能。发芽前藜麦种子中快消化淀粉、慢消化淀粉及抗性淀粉的百分含量分别为38.45%、43.64%和17.90%。发芽48h后,快消化淀粉的百分含量显著地增加至53.46%,而慢消化淀粉及抗性淀粉的百分含量分别下降至40.42%和6.11%。此外,发芽后藜麦种子中总皂苷含量显著增加了16.46%。研究表明,发芽的藜麦种子含有更好的营养价值和消化性能,可以用于加工功能性食品,促进人体健康。     

Physicochemical and rheological properties of purees based on Mafafa (Xanthosoma robustum) and quinoa (Chenopodium quinoa Willd.) with the addition of cryoprotectants

Growing interest in processed frozen products with similar characteristics to natural products has generated the study of new products in the food industry field. The characteristics of each matrix, the process of elaboration, composition, and structure of the additives and the interactions amongst these modify the food's texture, structure, physical and sensory properties and, hence, interfere directly with consumer acceptance. This research studied the effect of adding cryoprotectors during frozen storage on the rheological, physicochemical, structural, and microbiological properties in a Mafafa‐quinoa‐olive oil puree. To carry out the study, the rheological properties were determined through dynamic oscillatory tests and in steady state; likewise, the physicochemical properties (humidity, color, pH, and syneresis) were analyzed. Regarding physicochemical properties, the humidity content in the purees formulated varied between 57 and 74%, without important variation (p > .05) with respect to the formulation, however, in the storage during the freezing/thawing process, this parameter diminished in greater proportion in those purees containing carrageenan as cryoconservant. Both the addition of cryoconservants and the storage time affected significantly (p < .05) the puree's syneresis, with the degree of exudation being lower in the formulation containing xanthan gum at 1% w/w. During the freezing/thawing process, decreased apparent viscosity was noted. Additionally, the analysis of the viscoelastic properties of the purees evidences that already described, given that a significant effect (p < .05) was observed of the formulation of purees in the elastic component G′, in contrast with a notable decrease in the viscous component G″.     

藜麦营养功能成分及生物活性研究进展

藜麦是适宜人类食用的全营养食品,不仅含有丰富的蛋白质、淀粉、VB1、叶酸、矿物质（Ca、Zn、Fe）等营养物质,还含有多酚、黄酮、芦丁、槲皮素、异槲皮素、皂苷等功能成分,具有抗氧化、抗炎、降血糖、减肥等生理活性。本文综述藜麦的营养功能成分及其生物活性的国内外研究进展,并对其发展应用前景进行展望。     

Effects of microwave heating,steaming, boiling and baking on the structure and functional properties of quinoa (Chenopodium quinoa Willd.) protein isolates

The effects of microwave heating (MW), steaming (SM), boiling (BL) and baking (BK) on the structure and functional properties of quinoa protein isolates (QPI) were investigated. SDS-PAGE showed the 20–30 kDa band strength of QPI-BL was enhanced, which indicated the disulphide bond was broken and protein molecules dissociated. Due to the recombination of subunits, some large molecular weight or insoluble polymer components of QPI-SM and QPI-BK did not pass through the gel. Microwave heating and boiling showed negative effects for α-helix and positive effects for β-sheet, which implied the molecular structure was transformed from ordered to disordered, the secondary structure became loose. The reduction of free SH (sulfhydryl) and surface hydrophobicity implied that aggregation and cross-linking of protein molecules for QPI-SM and QPI-BK. QPI, QPI-MW and QPI-BL exhibited better solubility, which was related to the water holding capacity (WHC) and emulsification. For QPI-SM and QPI-BK, functional properties (including solubility, WHC and gel-forming ability) decreased due to molecular aggregation. Heat treatments significantly affect the structure and functional properties of QPI, the current research showed that microwave heating and boiling might be better heat treatment methods for QPI and would help the development of quinoa protein products.     

挤压膨化处理对藜麦营养成分及体外酵解特性的影响

本研究采用挤压膨化技术对藜麦进行处理,分析处理后藜麦营养成分变化,并结合体外酵解实验,探究挤压膨化处理对藜麦酵解特性的影响。结果表明,挤压膨化能显著降低藜麦中直链淀粉、脂肪、总膳食纤维和不可溶性膳食纤维含量（P＜0.05）,并显著增加可溶性膳食纤维含量（P＜0.05）。体外酵解实验中,随着酵解时间的延长,培养基中产气量不断增加,pH值在发酵前期显著降低（P＜0.05）。相较于空白对照,挤压膨化处理后藜麦能显著上调体外酵解过程中普雷沃氏菌、巨单胞菌、巨球形菌、考拉杆菌、双歧杆菌以及拟杆菌等的相对丰度（P＜0.05）,显著下调瘤胃菌科和肠杆菌科的相对丰度（P＜0.05）。同时,各组发酵产物中短链脂肪酸浓度均增加,且发酵48 h结束时挤压膨化处理后藜麦组高于空白对照组。综上,挤压膨化能影响藜麦的营养组成,其制品作为发酵底物能有效改善肠道菌群,有益于肠道健康。该研究可为通过挤压膨化处理获得藜麦制品及其促进肠道健康产品的开发提供数据支持。     

Comparison of the stability of palm olein and a palm olein/canola oil blend during deep‐fat frying of chicken nuggets and French fries

Stability of palm olein (PO) and a blend 50% palm olein/50% canola oil (POC) during deep‐fat frying at 180 °C of French fries (FF) or chicken nuggets (CN) was studied through the determination of physical and chemical parameters in the fresh and used oils. Degradation at the end of the study resulted in total polar compounds of 12–13.5% for PO and 11.5–14.5% for POC and viscosity of 65–123.3 cP for PO and 63–72.8 cP for POC. Lower peroxide values (5.33–6.32) were obtained for the blend (PO had 5.21–8.55). Food type affected colour parameters and p‐anisidine value of the oils. For CN, the lowest fat content and higher hardness were obtained when they were fried in PO. CN caused a faster deterioration in the oils, in comparison with FF, especially in POC. Gas chromatography allowed to observe differences in fatty acids composition for both used oils.     

Saponins of quinoa (Chenopodium quinoa): Effects of processing on their abundance in quinoa products and their biological effects on intestinal mucosal tissue

Quinoa (Chenopodium quinoa) is a valuable source of protein in some parts of South America, and it is likely to be exploited further in both developing and industrialised countries. However, quinoa seeds contain significant levels of saponins which are potential antinutrients. In the present study, the effects of processing on the quantity and composition of saponins in quinoa products were determined, and the biological effects of quinoa grain and cereal products containing high or low levels of saponins were investigated both in vitro and in vivo in the rat. Quinoa saponins were shown to be membranolytic against cells of the small intestine and to cause an increase in mucosal permeability in vitro. Unwashed bitter quinoa caused a significant food aversion and poor food conversion efficiency in rats. However, processing quinoa, during the manufacture of an infant cereal, reduced the concentration and membranolytic activity of saponins, and increased the palatability and nutritional quality of the cereal product to a level similar to that of a wheat-based cereal product.     

Effects of microwave heating on the quality characteristics and thermal properties of RBD palm olein

In the present work, the influence of microwave power (low-, medium- and high-power settings) and heating time on lipid deterioration produced during the microwave heating of RBD palm olein (RBDPO_O) was evaluated. The changes in thermal profiles by differential scanning calorimetry (DSC) were studied in comparison to the changes in chemical parameters. The DSC method was based on the cooling and melting curves of oils at a scanning rate of 5 °C/min. The chemical evaluation of the oils was based on free fatty acid content, C18:2/C16:0 ratio, peroxide, iodine, and anisidine values. The DSC results were explained on the basis of the endo- or exothermic peak temperatures. A statistical comparative study was carried out on the DSC and chemical parameters. The results indicate that there is a good correlation between the DSC and chemical methods. Based on the results obtained, the DSC appears to be a useful instrumental method in monitoring the oxidation of microwave heated oils, and it may have the potential to replace the time- and chemical-consuming standard chemical methods.     

An investigation on the physicochemical characterization of interesterified blends of fully hydrogenated palm olein and soybean oil

In this study, the effect of interesterification (using sodium methoxide) on physicochemical characteristics of fully hydrogenated palm olein (FHPO)/soybean oil blends (10 ratios) was investigated. Interesterification changed free fatty acid content, decreased oil stability index, solid fat content (SFC) and slip melting point (SMP), and does not affected the peroxide value. With the increase of FHPO ratio, oil stability index, SFC and SMP increased in both the interesterified and non-interesterified blends. Fats with higher FHPO ratio had narrower plastic range, as well. Compared to the initial blends, interesterified fats had wider plastic ranges at lower temperatures. Both the non-interesterified and interesterified blends showed monotectic behavior. The Gompertz function could describe SFC curve (as a function of temperature, saturated fatty acid (SFA) content or both) and SMP (as a function of SFA) of the interesterified fats with high R² and low mean absolute error.     

藜麦萌发过程中营养物质变化规律及藜麦芽乳制浆工艺研究

为进一步开发利用藜麦芽类产品,以藜麦为原料,经一定条件萌发,分别测定藜麦萌发后蛋白质、粗脂肪、淀粉、还原糖含量、α-淀粉酶、β-淀粉酶活性、维生素B1、B2含量、多酚、黄酮以及γ-氨基丁酸（GABA）含量的变化规律,并确定最佳萌发时间。在单因素的基础上采用正交实验优化,以原料利用率和多酚提取率的综合水平值作为评价指标,探寻藜麦芽乳最佳磨浆工艺。结果表明,最佳萌发时间为第3 d,磨浆温度为60℃,磨浆时间为3 min,磨浆液料比为6∶1 m L/g,磨浆p H为6.5时工艺最佳。此条件下原料利用率达到70.91%,多酚提取率为79.79%,综合水平值为77.13%。      

Antioxidative effects of alpha-tocopherol and ascorbyl palmitate on thermal oxidation of canola oil

Canola oil, with and without added alpha-tocopherol and ascorbyl palmitate, was used to deep-fat frying potatoes once per day for 10 day or once per week for 10 weeks. Changes in chemical and physical properties were monitored. Refractive index, free fatty acids and absorbance at 232 and 270 nm increased with frying time. Smoke point, 'L' color index, iodine value and the C18:2/C16:0 ratio in the oil decreased with the frying time. According to smoke point, which shows the time of the oil should be discarded, canola oil without antioxidant (control) can be used safely 8 times daily or 7 times weekly. For canola oil with antioxidant (oil + alpha-tocopherol + ascorbyl palmitate), the smoke point did not decrease below 170 degrees C in both daily and weekly fryings. This showed that canola oil with antioxidant could be used safely at least 10 times for both frying intervals. In both daily and weekly fryings, the addition of 200 ppm alpha-tocopherol and 200 ppm ascorbyl palmitate increased the oxidative stability of canola oil.     

油腊煎炸品质变化对油炸面制品保质期影响的研究

分析油脂在煎炸过程中品质的变化以及对油炸面制品保质期的影响.实验表明,油脂在煎炸过程中,其理化指标发生明显变化,不同油品煎炸面制品,保质期差异显著.     

秦岭山脉野生蒲公英提取物的抗氧化活性及其对胡麻油氧化稳定性的影响

以秦岭山脉野生蒲公英全草为原料,采用超声波纤维素酶同步法提取总活性成分。对蒲公英提取物的DPPH自由基清除能力、超氧阴离子自由基清除能力、羟自由基清除能力和总还原能力进行了测定,并与人工合成VC进行了比较,同时采用加速氧化的方法评价蒲公英提取物对胡麻油氧化稳定性的影响,并与BHT、迷迭香提取物进行比较。结果表明:蒲公英提取物比人工合成VC有更高的抗氧化活性; 3种抗氧化剂抗氧化能力大小为迷迭香提取物(700 mg/kg)>蒲公英提取物(700 mg/kg)> BHT(200 mg/kg),并且蒲公英提取物添加量与胡麻油的氧化稳定性呈正相关。因此,秦岭山脉野生蒲公英全草总活性成分提取物可作为天然抗氧化剂用于延缓食用油氧化。     

Effects of roasting conditions of sesame seeds on the oxidative stability of pressed oil during thermal oxidation

Oxidative stability of sesame oil (SO) prepared from sesame seeds roasted at 213, 230, and 247 °C for each 14, 21, or 28 min was determined at 180 °C heating condition by 2,2-diphenyl-1-picrylhydrazyl (DPPH), conjugated dienoic acid (CDA) value, headspace oxygen analysis, and profile changes of sesamol and sesamolin. As sesame seeds were roasted with longer time and higher temperature, more sesamol was found in SO. SO from sesame seeds roasted at 247 °C for 28 min had the highest oxidative stability based on the results of CDA and headspace oxygen. Absorbance of DPPH from SO roasted at 230 and 247 °C showed different patterns compared to those from SO at 213 °C during thermal oxidation. Sesamol was continuously generated with the decrease of sesamolin in SO from 230 to 247 °C while sesamol in SO from 213 °C did not increase during 180 °C heating. Higher oxidative stability of SO may be related with the continuous generation of sesamol from the degradation of sesamolin during thermal oxidation rather than the initial antioxidant content.