Fracture Intensity Distributions during Compression of Puffed Corn Meal Extrudates: Method for Quantifying Fracturability

The distribution of fracture intensities occurring during compression of puffed corn meal extrudates was described using an exponential function, and parameters from that analysis were used as fracturability indices. Since “jagged” or oscillating stress-strain functions are typical for porous and brittle materials, fracture intensities were determined by measuring the abrupt, sequential reductions in stress produced during compression. Both distribution exponent and cumulative fracture stress correlated strongly with fracturability measured by other techniques, including fractal and Fourier analysis of stress-strain functions. Distribution parameters also indicated textural differences due to process parameters (structural modification through addition of different levels of sucrose) and storage conditions (equilibration at various relative humidities).     

Low-fat, High Added Water Bologna from Massaged, Minced Batter

Bolognas were manufactured to produce a high-fat (30% fat), 10% added water (AW) formulation and three low-fat treatments which contained 10% fat/30% AW. Lean and fat trim for the low-fat treatments were blended and minced before massaging intermittently (10 min on/20 min off) for 0, 2.5 and 5.0 hr. Massaging did not affect pH or cook/chill losses but increased batter viscosity. Massaging generally increased purge accumulation, regardless of degree of vacuumization. Sensory and instrumental determinations indicated massaging up to 2.5 hr increased (P<0.05) cohesiveness. In addition, particle definition was decreased. There were no differences (P>0.05) in hardness among low-fat treatments. Massaging resulted in low-fat products that were less cohesive, softer, and more juicy than high-fat bologna.     

Accelerated Maturation of Cheddar Cheese: Influence of Added Lactobacilli and Commercial Protease on Composition and Texture

The addition of live and heat-shocked Lactobacillus casei-casei L2A and Neutrase© was tested for its ability to accelerate the maturation of Cheddar cheese. An evaluation of physicochemical and rheological properties showed that cheese pH was decreased by bacterial and enzymatic additives, while fracturability and cohesiveness were influenced principally by Neutrase. The integrated process recommended is composed of three parts: first, the addition of live L. casei-casei L2A to control the undesirable microflora, second, heat-shocked cells of the same species at a concentration of 1.0%, and third, Neutrase at a concentration not higher than 1.0 × 10^-5 AU/g of cheese. This process led to a good-quality sharp Cheddar cheese with 60% increase in flavor intensity compared to control cheese.     

造纸法烟草薄片脆性的评价方法

为建立一种客观评价造纸法烟草薄片脆性的方法,采用质构仪对不同含水率的1#造纸法烟草薄片样品进行撕裂测试和拉伸测试,分析测试结果与样品含水率的关系;采用质构仪对国内不同种类(1#~4#)造纸法烟草薄片进行撕裂测试,分析该方法的准确性.结果表明:无论撕裂测试是纵向还是横向,样品的正峰个数与含水率的相关系数(R2)最高,分别为0.938 0、0.954 8,说明撕裂测试时正峰个数能够表征造纸法烟草薄片的脆性;撕裂测试时国产造纸法烟草薄片的正峰个数与其手感脆性相对应,该方法能够准确评价和区分各类国产造纸法烟草薄片的脆性.     

Total frying-use time effects on soybean-oil deterioration and on tortilla chip quality

Refined soybean oils were degraded at 190°C for 60h to a total polar material of 61.54%. The effect of fresh to highly degraded oil on the physical and thermal properties of the oil as well as on the Final quality of tortilla chips was determined. Surface tension decreased significantly with oil degradation (P < 0.05). Colour readings also changed significantly with oil degradation (P < 0.05) and were more pronounced after 30h of frying. Foam and off-flavour developed between 20 and 30h of degradation suggesting that the oil should have been discarded when the total polar material reached 27%. The convective heat transfer coefficient changed more rapidly after 30h of frying. The values of the convective heat transfer coefficient correlated highly with viscosity (−0.98). The oils, whether fresh or degraded, behaved as Newtonian fluids. Viscosity was significantly affected by oil degradation time and temperature (P < 0.05). The effect of temperature on the viscosity of the oils was described by an Arrhenius equation. Viscosity changed more rapidly with temperature as the degradation time increased. Tortilla chips were fried in fresh and degraded soybean oils. Total oil content and fracturability of tortilla chips were not affected significantly by oil degradation time (P < 0.05). However, the oil content adhering to the surface of the tortilla chips was significantly higher (P < 0.05) in the tortilla chips fried in degraded oil than in fresh oil.     

酸菜自然发酵过程中的质地变化

以自然发酵酸菜为研究对象,应用质构仪质地多面分析(Texture Profile Analysis,TPA)法对自然发酵过程中酸菜质地变化进行分析,探讨了质构仪各项参数之间的相关性及自然发酵过程中各参数的变化规律。结果表明,大多数的质构参数之间呈现显著相关性,酸菜的硬度1、脆度、回复性、凝聚性及咀嚼性随着发酵时间的延长整体呈现下降的趋势,且发酵40～60 d时是食用酸菜品质最佳的时期。     

腐竹热干燥特性及工艺优化研究

为缩短腐竹热干燥时间,得到色差,碎裂性及感官指标均最优的腐竹,对腐竹热干燥工艺进行优化。通过60、70、80、90、100℃恒温干燥腐竹,结果显示：90℃和100℃条件下可明显缩短干燥时间,但腐竹色差和感官效果不可接受;60～80℃范围内干燥,腐竹品质相近,色差较好,但易碎。设计高温→低温和低温→高温共5种温度梯度干燥方案,得到腐竹干燥最佳方案：100℃＋风＋1h→80℃＋风＋1.5h→60℃＋1.5h,共耗时4h。得到的干腐竹L＊值下降幅度小,a＊值上升幅度小,b＊值稳定;硬度和碎裂度值均达到最大值;感官上,腐竹表面出油很少,淡黄色,光泽好,豆香味浓郁,结实不易碎。