Quality and Acceptability of Microwave and Conventionally Pasteurised Kiwifruit Puree

The development and optimisation of food preservation processes seem to be necessary in order to address consumer expectations related to secure, fresh-like foods. To this end, the sensory, nutritional and functional properties must be maximally retained. In order to contribute to the acquisition of knowledge about the adequacy of microwave processing as a means of preserving fruit-based products, the present study compares the impact of microwave heating with conventional thermal processing. The consumer acceptance of fresh and pasteurised kiwifruit puree was studied as was the content of water, soluble solids and bioactive compounds and the pH, consistency, viscosity, colour coordinates and antioxidant capacity, as well as the effect of the thermal treatment on enzyme and microbial inactivation. As bioactive compounds, the content of vitamins C, A and E and the total flavonoid, phenol and tannin content have been considered. As the obtained results show, not only was microwaved puree preferred by consumers, but it also exhibited a superior maintenance of the nutritive and functional properties of the fruit, smaller colour changes and a content of inactivated enzymes and microorganisms equal to or greater than the conventionally heated sample.     

Effects of Heating System, Temperature and Rate of Heating on Sensory Characteristics of Beef

Sensory scores for appearance and texture of oven-roasted beef semitendinosus were compared with those of samples heated in glass tubes in a water bath. Roasts heated in 93 and 149°C ovens appeared to be less done and were moister than water bath samples heated at comparable rates. Samples heated to 60°C in both systems appeared to be less done and were moister and less mealy than samples heated to 70°C. Few differences in sensory scores for textural parameters were attributed to heating system, endpoint or heating rate. Correlations between scores for intact roasts and objective measurements for the small samples were not always of the same direction or strength as were the relationships between scores and objective values for roast samples.     

微波加热对小龙虾品质的影响

为了挖掘微波在小龙虾热加工中的应用潜力,本文以水煮小龙虾为对照,通过热成像温度分析、摄影图像色泽分析、质构和脱壳完整率分析以及感官分析等方法,全面地分析了不同功率密度的微波加热对小龙虾品质(色泽、质构、脱壳完整率、质量损失等)的影响。结果表明,小龙虾在微波加热过程中的温度和表壳色泽分布不均,但高功率密度和长时间的微波加热有利于小龙虾温度和橘红色泽分布趋于均匀,其中5 W/g微波加热4.5和5.5 min的小龙虾外观评分分别与水煮4.5和5.5 min的小龙虾无显著性差异。随微波加热时间和功率密度的增加,小龙虾的质量损失和虾肉的水分流失随之增加,进而影响了虾肉的质构特性、剪切特性、挤压损失和口感。对于不同功率密度的微波加热,小龙虾虾尾的口感与其质构特性和剪切特性间的相关性存在差异,其中虾尾的口感与虾尾表面硬度、紧实度、含水量和挤压损失呈正相关,与虾尾剪切力、剪切能呈负相关。此外,3 W/g微波加热3.5 min的虾尾口感评分最高,且与水煮3.5 min的虾尾口感无显著差别,但非水环境下微波加热的小龙虾比水煮小龙虾更容易脱水且更难脱壳,这使得微波加热的小龙虾虾尾的形态和色泽较水煮更差。随着微波加热时间或功率密度的增加,微波小龙虾虾尾的L^*和b^*值有所增加,但虾尾的a^*值下降且脱壳完整率的改善不明显。综上,微波在小龙虾的热加工中具有一定应用潜力。     

蔗糖溶液中的微波热效应特征研究

介绍微波热效应的原理及其特点。利用微汉加热新技术进行清水和蔗糖溶液匠温升试验，结果表明，微波可快速加热清不和蔗糖溶液，并且糖液的浓度越高温度升得越快。     

微波加热对冷冻馒头品质特性的影响

研究微波加热对冷冻馒头温度、水分含量、质构特性等品质特性的影响。结果表明:增大微波功率可以缩短加热时间,对温度变化趋势及质构特性影响较小。直接微波加热时,中火功率更利于水分的保持;馒头表面涂水加热和微波加蒸汽加热延长了加热滞后期,都能减少馒头水分的流失,改善馒头加热后质构特性,尤以微波加蒸汽加热最为理想。因此,冷冻馒头微波加热的最佳条件:采用微波加蒸汽加热方式,高火,加热时间120s(质量约80g馒头)。     

Microbial and Sensory Effects of Combined High Hydrostatic Pressure and Dense Phase Carbon Dioxide Process on Feijoa Puree

High hydrostatic pressure (HHP) is used for microbial inactivation in foods. Addition of carbon dioxide (CO₂) to HHP can improve microbial and enzyme inactivation. This study investigated microbial effects of combined HHP and CO₂ on Escherichia coli, Bacillus subtilis, and Saccharomyces cerevisiae, and evaluated sensory attributes of treated feijoa fruit puree (pH 3.2). Microorganisms in their growth media and feijoa puree were treated with HHP alone (HHP), or saturated with CO₂ at 1 atm (HHPcarb), or 0.4%w/w of CO₂ was injected into the package (HHPcarb+CO₂). Microbial samples were processed at 200 to 400 MPa, 25 °C, 2 to 6 min. Feijoa samples were processed at 600 MPa, 20 °C, 5 min, then served with and without added sucrose (10%w/w). Treated samples were analyzed for microbial viability and sensory evaluation. Addition of CO₂ enhanced microbial inactivation of HHP from 1.7‐log to 4.3‐log reduction in E. coli at 400 MPa, 4 min, and reduction of >6.5 logs in B. subtilis (vegetative cells) starting at 200 MPa, 2 min. For yeast, HHPcarb+CO₂ increased the inactivation of HHP from 4.7‐log to 6.2‐log reduction at 250 MPa, 4 min. The synergistic effect of CO₂ with HHP increased with increasing time and pressure. HHPcarb+CO₂ treatment did not alter the appearance and color, while affecting the texture and flavor of unsweetened feijoa samples. There were no differences in sensory attributes and preferences between HHPcarb+CO₂ and fresh sweetened products. Addition of CO₂ in HHP treatment can reduce process pressure and time, and better preserve product quality.     

Structural Characteristics of Pumpkin Pectin Extracted by Microwave Heating

Abstract: To improve extraction yield of pumpkin pectin, microwave heating was adopted in this study. Using hot acid extraction, pumpkin pectin yield decreased from 5.7% to 1.0% as pH increased from pH 1.0 to 2.0. At pH 2.5, no pectin was recovered from pumpkin flesh powder. After a pretreatment at pH 1.0 and 25 °C for 1 h, pumpkin powder was microwave‐extracted at 120 °C for 3 min resulting in 10.5% of pectin yield. However, premicrowave treatment at 60 °C for 20 min did not improve extraction yield. When microwave heating at 80 °C for 10 min was applied after premicrowave treatment, final pectin yield increased to 11.3%. When pH was adjusted to 2.0, the yield dropped to 7.7% under the same extraction conditions. Molecular shape and properties as well as chemical composition of pumpkin pectin were significantly affected depending on extraction methods. Galacturonic acid content (51% to 58%) of pumpkin pectin was lower than that detected in commercial acid‐extracted citrus pectin, while higher content of neutral sugars and acetyl esters existed in pumpkin pectin structure. Molecular weight (M_w) and intrinsic viscosity (η_w) determined for microwave‐extracted pumpkin pectins were substantially lower than acid‐extracted pectin, whereas polydispersity was greater. However, microwave‐extracted pectin at pH 2.0 had more than 5 times greater M_w than did the pectin extracted at pH 1.0. The η_w of microwave‐extracted pectin produced at pH 2.0 was almost twice that of other microwave‐extracted pectins, which were comparable to that of acid‐extracted pectin. These results indicate that extraction yield of pumpkin pectin would be improved by microwave extraction and different pectin structure and properties can be obtained compared to acid extraction. Practical Application: Pumpkin is a promising alternative source for pectin material. Pumpkin pectin has a unique chemical structure and physical properties, presumably providing different functional properties compared to conventional commercial pectin sources. Depending on the conditions to produce pumpkin pectin, diverse molecular structures can be obtained and utilized in various food applications.     

Microwave Heating Effects on Relative Stabilities of Tocopherols in Oils

The relative stabilities of individual tocopherols during microwave heating were investigated in fatty acid esters and tocopherol-stripped vegetable oils. The rate of tocopherol loss during heating was less from the highly unsaturated ethyl esters or vegetable oils than from ethyl laurate or olive oil. However, changes in chemical properties of the substrates depended on degree of unsaturation of esters and oils. The stability of tocopherols during microwave heating was δ > β > γ > α, and the order did not change with differences in the type of ethyl esters of fatty acids or oils.     

菠菜粉对芋头粉糊化和菠菜芋泥流变特性与感官特性的影响

针对婴幼儿辅食中蔬菜补充不足的问题,以菠菜粉和芋头粉为原料制备菠菜芋泥,探究了菠菜粉对芋头粉糊化特性的影响,以及芋头粉添加量为5、10和15 g/100 mL时菠菜粉的添加量对菠菜芋泥流变特性与感官特性的影响。结果表明,菠菜粉的添加降低了芋头粉的峰值黏度、谷值黏度、最终黏度,改善了高温加工过程中芋头粉糊的稳定性,抑制了淀粉的回生。菠菜粉的添加提高了菠菜芋泥的储能模量（G'）和表观黏度。感官评价结果显示,菠菜粉的添加提高了菠菜芋泥的搅动阻力、滞留感和稠厚感,降低了其流动性。流变特性与勺搅拌阻力呈现出最强的正相关性,与口腔内流动性呈现出最强的负相关性。芋头粉添加量为10 g/100 mL的菠菜芋泥的流变特性符合婴幼儿果蔬泥的要求。在开发菠菜芋泥产品时,可通过增加菠菜含量来达到预期的感官指标。控制芋头含量并提高菠菜含量,有助于婴幼儿摄入适量的膳食纤维。     

Physical and Sensory Properties of Sweetpotato Puree Texturized with Cellulose Derivatives

We evaluated the physical and sensory characteristics of restructured sweetpotato puree texturized with methylcellulose (MC) or methylhy-droxypropylcellulose (MHPC). Samples were studied by instrumental texture profile (TPA), dynamic rheometric and sensory analyses, and scanning electron microscopy. Gelation of the gum-puree mixtures gave maximal values of the storage modulus (G^') at 60-70^°C. The TPA curves measured at 60^°C for the 0.50%MC or MHPC sample were similar to those of baked sweet potatoes (control). A texture profile panel rated the 60^°C samples of the 0.25-0.50%MC or MHPC product as nearly equal to baked roots for several texture notes. An untrained acceptability panel scored the 0.25%MC and MHPC samples significantly higher in flavor and overall acceptability than baked roots.     

Effects of Microwave Heating on the Molecular Species of Soybean Triacylglycerols

Microwave heating of whole soybeans resulted in an apparent increase of the total lipids. Molecular species of triacylglycerols were isolated from total lipids by a combination of silicic acid column chromatography and AgNO₃-thin layer chromatography (TLC). Fifteen molecular species of triacylglycerols were still found in whole soybeans following heat treatment. Microwave heating for about 5 min did not change all molecular species of soybean triacylglycerols nor cause a loss of unsaturated heat fatty acids. However, heat treatment for 8 min significant decrease not only in molecular species containing more than four double bonds, but also in the amount of diene and triene present in a triacylglycerol.     

Heating Characteristics of Milk Constituents in a Microwave Pasteurization System

A continuous pasteurization system was designed using a domestic microwave oven and heating characteristics were studied on water, cream, and milk constituents. Parameters were determined as functions of flow rate and power using water ≧ 75g/min (minimum flow at full power without boiling). Operation at less than 100% caused unacceptable temperature oscillations. Cream, milks and solutions of the individual milk constituents (fat, protein and lactose), were also assessed in attempts to determine relative contributions of each. Milk heated more rapidly than water and protein was the major contributor to heating, with fat and lactose-effects being negligible. The microwave system could heat solutions to temperatures needed for HTST pasteurization and was controlled by adjusting flow rate.     

Changes in Volatile Sulfur Compounds in Strawberry Puree during Heating

ABSTRACT: Solid-phase microextraction coupled with gas chromatography/pulsed flame photometric detection was used to monitor methane thiol, hydrogen sulfide, sulfur dioxide, dimethyl sulfide, carbon disulfide, methyl thioacetate, dimethyl sulfide, methyl thiobutyrate, and dimethyl trisulfide after heating strawberry puree at 95°C for 0, 0.5, 1.0, 1.5, 2.5, 4, and 10 min. After heating 10 min, dimethyl trisulfide increased from 0.11 to 0.41 ng/mL, and dimethyl disulfide decreased from 1.3 to 0.3 ng/mL. Concentrations of methyl thiobutyrate and methyl thioacetate were approximately 6 and 60 ng/mL, respectively, and essentially unaffected by heating. Dimethyl sulfide (cabbage aroma) was not detected in fresh puree but increased exponentially during heating, reaching a value of 500 ng/mL (100 × its odor threshold) at 10 min. Dimethyl sulfide was the major sulfur aroma impact compound in heated strawberry puree and a major contributor to the flavor change associated with heated strawberry puree.     

Turbot Fillet Sections Cooked by Microwave and Conventional Heating Methods: Objective and Sensory Evaluation

Greenland turbot fillet sections were baked in conventional and microwave ovens. The microwave oven cooked the fish faster, required less energy, and demonstrated greater relative efficiency than did the conventional oven. Solid-drip and total cooking losses were greater and Kramer shear values and evaporative loss were lower for microwave-heated fish. No differences in sensory flakiness and moisture were found between oven treatments, but microwave-heated samples were rated softer and less chewy by a trained panel. Several significant correlations were found among sensory attributes and objective measures of quality. A 39-member consumer panel indicated no differences in acceptability of turbot heated by the two cooking methods.     

微波加热对春卷物理特性的影响

研究了微波加热几种处理对冷冻春卷物理特性的影响。结果表明 :( 1)在 650W微波加热 2min后 ,春卷中心温度达到 110℃ ,高于外表面的 90℃ ,水分含量从 55 0 0 %迅速减少至 2 0 75% ,外表层水分含量从 31 70 %减到 13 30 % ,颜色值L =69 30 ,a =0 12 ,b =14 4 7,不会变焦黄色 ,质地变硬 ,断裂力和变形距离分别是 5 34N和 4 4 1mm。( 2 )微波加热前涂油处理可提高春卷的表面温度 ,使其于 2min后达到 110℃ ,整春卷及其表层水分含量分别为 30 85%和 16 18% ,水分的减少比无涂油处理的慢 ,但仍无法获得焦黄色 (L =63 0 3,a =- 0 2 9,b =12 32 )和酥脆的质地 ,断裂力和变形距离分别是 3 56N和 4 84mm。( 3)涂油和微波感受材料 (microwavesusceptor)包装处理 ,在 650W微波加热 2min后 ,春卷外表层温度上升至 160℃以上 ,而内部温度保持在 10 0℃ ,水分含量为 2 4 4 5% ,其中外表层水分因高温而迅速减少至 4 16% ,外表面大部分变得焦黄色 (L =54 67,a =6 56,b =2 2 2 8)和脆的质地 ,断裂力和变形距离分别为 3 11N和 2 96mm。     

水分和温度对猪肉质构及感官品质的影响

本文以猪里脊肉为原料,在感官评定、仪器分析的基础上,结合低场核磁共振测定结果,考察了水分条件及加热温度对猪肉制品品质的影响。实验数据表明:猪肉的感官硬度、紧密性及咀嚼感随含水量降低而升高,感官弹性略有改善,但100℃热处理的不同干燥样之间没有显著差异(p0.05);质构指标硬度、咀嚼性和剪切力值等与肉品的水分含量呈极显著负相关关系(p0.01);通过降低肉的含水量(36%)可改善121℃热处理导致的肉质软烂和硬度降低。通过LF-NMR分析发现:随干燥程度增大,各状态水分的T2弛豫时间均向快弛豫方向移动,加热温度越高,T21状态的水分弛豫时间移动越明显;干燥脱水造成的水分分布变化不及高温加热造成的影响显著;不易流动水与肉的质构特性关系相当密切,控制其含量可影响脱水肉制品的食用品质。     

Effects of Homogenization on Sensory Characteristics of Vanilla Ice Cream

Nine different batches of ice creams that contained no emulsifier and that had been processed at various homogenization pressures were compared with a reference ice cream batch that was processed by commercial techniques (an emulsifier added and homogenized double-stage at 140.74 and 35.18 kg/cm² (2000 and 500 psi), first and second stage, respectively). The samples were compared for seven sensory attributes: chewiness, greasy mouthcoating, iciness, vanilla flavor intensity, loss of shape, wheying off, and curdling. Data showed differences in loss of shape and vanilla flavor intensity in some of the samples when compared with the reference sample. Vanilla flavor intensity was more pronounced in experimental samples, which indicated that the emulsifier in the reference mix in some way suppressed vanilla flavor intensity.     

Effects of Microwave Heating on Solubility, Digestibility and Metabolism of Soy Protein

Microwave heating of soybeans for 9 min decreased protein solubility from 80 to 17%, from 81 to 18%, and from 72 to 16% when deionized H2O, 0.6N NaCl and 0.4N CaCl2, were used as solvents, respectively. Experiments were conducted to determine ‘in vivo protein digestibility and metabolizable nitrogen using male Sprague-Dawley rats. The percentages of true digestibility were found to be 73, 84, 87 and 81 when the soybeans were microwave heated for 0, 9, 12 and 15 min, respectively. Microwave heating soybeans up to 15 min did not alter the fatty acids composition of the beans.