Texture of Pecans Measured by Sensory and Instrumental Means

The texture of pecans (Carya illinoensis) from four cuhivars (Barton, Mahan, Western and Wichita) was analyzed using sensory and instrumental methods. Sensory hardness, flexibility and crispness were rated by trained panelists. Ranking of hardness and crispness was also carried out. A Texture Analyser TAXT2 was used for 50% compression, texture profile analysis (TPA), puncture and bending. Puncture and 50% compression gave best reproducibility, least variability and agreement with sensory data. The most relevant TPA parameters were cohesiveness, elasticity and fracturabihty. Parameters from the bending test did not indicate texture of the pecans suitably.     

Texture of Glassy Corn Cakes as a Function of Moisture Content

Glass transition temperatures of yellow and white corn cakes were investigated within the moisture range of 2 to 32% (w/w) using dynamic differential scanning calorimetry. All measurements were conducted at 10°C/min heating rate, 30 sec equilibrium period, and 1°C amplitude. Effects of water plasticization on corn cakes were predicted by the Gordon-Taylor's equation. Moisture sorption isotherms were established using BET and GAB equations. Relationships were found among glass transition temperature, moisture content and cake texture. The loss of crispness of corn cakes occurred within the glassy state. The initial loss of crispness occurred around monolayer moisture content, and the complete loss of crispness occurred at about 9% moisture with the highest hardness.     

Impact of Almond Form and Moisture Content on Texture Attributes and Acceptability

The objectives of this study were to measure sensory texture attributes of 5 types of almonds (blanched slivered, natural sliced, whole blanched, whole dry roasted, and natural whole) conditioned at 4 different moisture levels, to measure liking of a subset of these products, and to compare the sensory texture measurements with consumer liking ratings. Thirteen panelists trained to evaluate almond texture rated the texture attributes of the 20 almond samples. A panel of 113 almond consumers rated their liking of a subset of 8 of these almonds. Compared with the whole almonds, sliced and slivered almonds had less hardness, less crunchiness, less cohesiveness, less tooth packing, and required fewer chews and swallows to consume. Compared with slivered almonds, sliced almonds were more powdery, had more surface roughness, more loose particles, and were crisper. Compared with slivered almonds, sliced almonds were less hard, broke into fewer pieces, had less moistness and cohesiveness of mass, less fatty film, and required fewer chews and fewer swallows to consume. Dry roasted almonds were generally harder, more crisp, more crunchy, and produced more loose particles than natural almonds, which were, in turn, more hard, crisp, and crunchy than blanched almonds. As moisture content increased, moistness of mass and cohesiveness of mass increased. Crispness, number of pieces, hardness, crunchiness, persistence of crunch, and particulate mass decreased with increasing moisture content. Consumer texture liking ratings were highly positively correlated with the attributes crispness, crunchiness, and persistence of crunch.     

不同水分含量对南极磷虾烤虾质构和色泽的影响

以质构和色泽为指标,并结合感官评定,对水分含量分别为22％、25％、28％和31％的四种南极磷虾烤虾品质进行研究。实验结果表明,水分含量对南极磷虾烤虾质构有一定影响,水分含量22％的南极磷虾烤虾的硬度、胶粘性、咀嚼性和剪切力与其他水分含量的南极磷虾烤虾呈显著性差异（P〈0．05）,水分含量25％和28％的南极磷虾烤虾的内聚性和弹性相对较高,品质较好;通过测定四种烤虾的RG雅,发现四种样品的色泽均属于粉色系,对外观的影响不是很大,随着烤虾水分含量下降,制品的色泽越容易接受。水分含量28％的南极磷虾烤虾的感官评分最高,为8．99±0．05,通过对不同水分含量的南极磷虾烤虾的质构和色泽分析,结合感官评定,认为南极磷虾烤虾的水分含量为28％时品质最佳。     

Pecan Texture as Affected by Freezing Rates, Storage Temperature, and Thawing Rates

Pecan texture was measured by texture profile analysis (TPA) at 80% compression before and after being frozen at 6 controlled rates, to 3 minimum temperatures and thawed at 2 rates. Freezing and thawing rates had more influence than storage temperature on pecan texture. Certain TPA parameters (i.e., hardness, area 1, fracturability and slope of linear segment of force vs. deformation curve) were more affected than others by freezing and thawing rates. Freezing and thawing at high rates had the least effect on pecan texture.     

Pecan Kernel Breakage and Oil Extracted by Supercritical CO2 as Affected by Moisture Content

During supercritical CO₂ extraction of oil from pecans, kernel breakage frequently occurs when the depressurization time is short. The purpose of this study was to investigate the effects of initial moisture content of pecan kernels and moisture equilibration time on pecan breakage and oil recovery when extracting with supercritical CO₂. Initial pecan moisture content, adjusted to 3.5% to 11.0%, had a significant effect on breakage when using a short depressurization time. With higher pecan moisture, less kernel breakage occurred. Increasing moisture equilibration time from 1 to 48 h reduced kernel breakage and produced an average of 30% more oil during extraction. Moisture content did not significantly affect the amount of oil extracted.     

Tocopherol Quantification by HPLC in Pecans and Relationship to Kernel Quality during Storage

Changes in tocopherols were followed in Stuart, Desirable and Schley cultivars during storage at 23.9°C and 60-70% RH and 0.6°C and 75% RH for 12 mo. Quality changes in the pecans were monitored using Hunter color measurements and conjugated diene measurement. α-, β-,γ- and 8-tocopherols were found in the three cultivars and γ-tocopherol was the primary form in each. Decreases of γ- and total tocopherols and L, hue angle and saturation index values were observed for pecans stored at 23.9°C (P < 0.05). Positive correlations (P < 0.05) were found between γ- and total tocopherols and Hunter color values for samples stored at 23.9°C. Conjugated diene levels did not correlate with tocopherol levels and Hunter values (P < 0.05). Pecans could be stored at 0.6°C and 75% RH for 12 mo without changes in kernel color, oil quality, tocopherols or conjugated diene levels.     

Oxidative Stability in Raw and Roasted Pecans: Chemical, Physical and Sensory Measurements

To develop predictive relationships for sensory responses of crunchiness and rancid aroma and flavor, raw and roasted pecans were stored under two different relative humidities (55 and 65%) up to 8 mo. In response to relative humidity, rancid scores did not differ with either raw or roasted pecans. Rancid scores in raw and roasted pecans during storage most closely paralleled peroxide value and thiobarbituric acid reactive substances, respectively. Multiple regression models employing two or three oxidative and chemical measurements led to better prediction of sensory scores. In general, primary oxidative products of triacylglycerols factored into the models for raw pecans while secondary oxidative products of total lipids factored into the models for roasted pecans.     

Effects of Variety and Crop Year on Tocopherols in Pecans

Alpha‐, beta‐, gamma‐, and delta‐tocopherols (α‐, β‐, γ‐ and δ‐T) were quantified in pecans (seedlings, Desirable, Stuart and Schley) of 2 crop year by using a direct extraction method coupled with normal‐phase HPLC. % recoveries of the assay were about 98, 92, 97, and 97 for α‐, β‐, γ‐ and δ‐T, respectively. Accuracy was excellent with low % CVs for all tocopherols. Overall precision was good except for δ‐T, which was not resolved from an unidentified interference. There were significant differences in tocopherol contents among cultivars (p < 0.05). No significant difference was observed in α‐TE (tocopherol equivalent) between 1998 and 1999 crop year for Stuart and Schley (p > 0.05), but α‐TE content of Desirable and seedling did vary (p < 0.05). γ‐T was the predominant tocopherol for all pecan samples ranging from 20.1 to 29.3 mg/100 g. α‐, β‐, and δ‐T occurred in low levels. Tocotrienols were not present. α‐TE ranged from 3.3 to 4.2 in the different cultivars.     

转谷氨酰胺酶诱导调质大豆分离蛋白凝胶的水分分布及凝胶特性

利用低场核磁共振技术、质构仪、差示扫描量热仪等对调质大豆分离蛋白凝胶水分分布、凝胶特性及微观 结构进行测定,研究调质大豆分离蛋白的蛋白组成对转谷氨酰胺酶诱导的蛋白凝胶的影响。结果表明：调质大豆分 离蛋白中11S球蛋白所占比例对蛋白凝胶水分分布、凝胶特性及微观结构有显著相关性。11S球蛋白的质量分数由 60%提高到80%时,蛋白凝胶的横向弛豫时间T2先缩短后延长;凝胶的硬度、黏性、咀嚼性3 项指标值均有不同程 度的降低;蛋白凝胶的热稳定性先提高后降低,70%的11S球蛋白蛋白凝胶ΔH最低,凝胶中水分不易失去;11S球 蛋白质量分数分别为60%与70%的大豆分离蛋白凝胶形成的微观结构表面较平整,孔洞较小且相对均匀。     

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。     

不同烹调方法对鱼营养价值及感官评价的影响

通过分析鲟鱼和罗非鱼经清蒸、微波、微波烤、烤箱烤、油煎、高压6种不同烹调处理后水分、脂肪含量的变化,探讨烹调后水分、脂肪含量与质构特性和感官特性的相关性,找到适合水产品烹调方式,使水产品的营养价值得到最大的保存率,以此指导人们合理膳食。结果表明：清蒸烹调后水分含量最大,整体可接受性最高。相关性分析表明：烹调后样品的水分含量与多汁性及弹性有显著正相关性,而脂肪含量与硬度有极显著负相关性,与内聚性具有负相关趋势。以质构指标预测感官特性的预测方程构成因鱼种而有所差异。     

基于低场核磁共振分析与成像探究贮藏过程中板栗水分迁移对其质构变化的影响

本文为探究水分迁移对板栗品质的影响,以黔产仓更板栗为试验原料,运用LF-NMR、TPA检测技术,研究板栗采后贮藏期间水分含量、水分相态变化、质构变化及其相关性。结果表明:黔产仓更板栗出仁率高;板栗含结合水、不易流动水、自由水,贮藏期间板栗不易流动水转化为结合水、自由水,稳定板栗内部结构;板栗水分含量与板栗质构指标内聚性、弹性呈显著正相关(P<0.05);板栗水分中不易流动水与板栗内聚性、弹性呈显著正相关(P<0.05);板栗自由水与板栗弹性呈显著正相关;板栗结合水的变化对板栗品质无显著性影响。研究结果为后续深入研究板栗脱水敏感性和安全含水量,促进板栗保鲜、保质奠定了基础。     

用木材测湿仪测量竹篾含水率的研究

研究了用木材测湿仪测量竹篾含水率的修正问题。根据烘干法通过线性回归分析对测量结果进行了修正,并计算了拟合优度,检验了回归关系的显著性和回归残差的分布,结果表明,用木材测湿仪测量竹篾含水率按回归方程y=1.172x-8.843修正是可行的。     

浅谈木材含水率对刨花板生产的影响

阐述在刨花板生产过程中,含水率对木质原料储备、木片制备、刨花制备、刨花干燥、调施胶、热压的影响。     

Moisture Diffusivity in Sponge Cake as Related to Porous Structure Evaluation and Moisture Content

ABSTRACT: Water diffusivity within sponge cake was determined at 5, 20, and 25 °C by identification from a water sorption kinetic and using a mathematical model based on Fick's 2nd law. Water diffusivity at 20 °C within sponge cake varied from 0.5 × 10^-10 m²/s to 7.5 × 10^-10 m²/s as a function of sponge cake moisture content. Influence of temperature on the concentration-dependent diffusivity was investigated. The activation energy was found to vary with sponge cake moisture content from 84 to 128 kj/mole. Effective diffusivity variations were correlated with the changes in microstructure of the material that was observed by using environmental scanning electron microscopy. The level of porosity in the material played a dominant role in determining the effective diffusivity.     

Application of Image Texture Analysis for Online Determination of Curd Moisture and Whey Solids in a Laboratory-Scale Stirred Cheese Vat

ABSTRACT:  A noninvasive technology, which could be employed online to monitor syneresis, would facilitate the production of higher quality and more consistent cheese products. Computer vision techniques such as image texture analysis have been successfully established as rapid, consistent, and nondestructive tools for determining the quality of food products. In this study, the potential of image texture analysis to monitor syneresis of cheese curd in a stirred vat was studied. A fully randomized 2-factor (milk pH and stirring speed), 2-level factorial design was carried out in triplicate. During syneresis, images of the surface of the stirred curd–whey mixture were captured using a computer vision system. The images were subjected to 5 image texture analysis methods by which 109 image texture features were extracted. Significant correlations were observed between a number of image texture features and curd moisture and whey solids. Multiscale analysis techniques of fractal dimension and wavelet transform were demonstrated to be the most useful for predicting syneresis indices. Fractal dimension features predicted curd moisture and whey solids during syneresis with standard errors of prediction of 1.03% (w/w) and 0.58 g/kg, respectively. It was concluded that syneresis indices were most closely related to the image texture features of multiscale representation. The results of this study indicate that image texture analysis has potential for monitoring syneresis.     

论小麦水分调节的力学效应与潜伏功能

论述了小麦制粉前水分调节的意义和水分的力学效应。通过对全粒小麦、麦皮、麦胚进行不同水分下的抗力实验,证明润水可以创造皮心分离的条件,但是加水量多少和润麦时间的长短都与水分的力学效应有很大关系,应根据粉路的长短,制定合适的润麦水分和润麦时间。并以某面粉厂为例,详细介绍了制粉各系统出粉量粉质和水分的变化。