Solid State Ethanol Fermentation of Apple Pomace as Affected by Moisture and Bioreactor Mixing Speed

Solid state ethanol fermentation was conducted on apple pomace in a 40 L capacity horizontal batch reactor at 30°C using apple pomace moisture contents of 77 and 85% wb, mixing speeds of 2, 20 and 40 rpm and Saccharomyces cerevisiae ATCC 24702. A higher mean maximum ethanol concentration of 19.26% db was obtained at 85% wb moisture, whereas a mean ethanol of 18.10% db was produced at 77% wb pomace moisture. Mean ethanol concentrations during fermentation of 10.79 and 10.27% db, at bioreactor mixing speeds of 2 and 20 rpm, respectively, were significantly higher than the corresponding value of 9.30% db obtained at 40 rpm mixing speed. Maximum ethanol concentrations were attained earlier at 2 and 20 rpm than at 40 rpm. A linear regression model for fermentation efficiency was fitted as a function of initial glucose and moisture.     

顶空固相微萃取- 气相色谱- 质谱法测定苹果渣发酵蒸馏酒的香气成分

以顶空固相微萃取-气相色谱-质谱法测定苹果渣发酵蒸馏酒和酒精浸泡苹果渣蒸馏酒中的香气成分。经过鉴定分析,在苹果渣发酵蒸馏酒中,共测得57种挥发性香气成分,其中酯类物质30种、羧酸类物质5种、醇类物质6种、酮类物质1种、烃类物质14种、其他香气物质1种,相对含量分别占总挥发性香气物质的50.604%、6.322%、22.207%、0.254%、20.542%、0.013%;在酒精浸泡苹果渣蒸馏酒中,共测得37种挥发性香气成分,其中酯类物质22种、羧酸类物质3种、醇类物质2种、烃类物质9种、其他香气物质1种,相对含量分别占总挥发性香气物质的64.272%、2.538%、14.885%、17.437%、0.911%。通过比较分析,苹果渣发酵蒸馏酒中香气成分的种类显著多于酒精浸泡苹果渣蒸馏酒,香气成分分布更加均匀,口感更加醇厚自然,层次感更强。发酵结束后,酒体在保留苹果渣中营养成分的同时,也具有苹果的独特香气。研究说明苹果渣用于生产发酵蒸馏酒是更加利于其综合利用的一种途径。     

Effects of Salt, Sugar and Screw Speed on Processing and Product Variables of Corn Meal Extruded with a Twin-Screw Extruder

The effects of screw speed and additives (sugar and salt) on processing and product variables of corn meal extruded with a twin-screw extruder were studied. Higher salt (0–3%) and sugar concentrations (0–4%) in the feed decreased the die pressure, % torque and specific energy. But at 6 and 8%, sugar increased the three processing parameters. Higher screw speed (250 vs 200 rpm) decreased die pressure and % torque, but increased specific energy. The addition of salt and sugar enhanced extrudate radial and axial expansions, but reduced product bulk density and breaking strength. An increase in screw speed decreased radial expansion and bulk density, but increased axial expansion and breaking strength.     

螺杆转速对持香型仿肉制品结构及挥发性成分保留率的影响

本研究以大豆分离蛋白及谷朊粉为主要原料,以天然呈味粉末油脂为香气调味料,利用高湿挤压技术制备持香型仿肉制品。通过固相微萃取-气相色谱-质谱联用、扫描电子显微镜、核磁共振及傅里叶变换红外光谱分析,确定螺杆转速对持香型仿肉制品挥发性风味物质保留率、微观结构、水分分布、蛋白结构的影响。结果表明挥发性风味物质保留率总体随螺杆转速的增加有先增多后减少的变化趋势,在300 r/min时最大,且仿肉制品较紧密的微观结构、较小的水分子运动自由度及蛋白质二级结构的展开均有利于风味物质的保持。     

Biomass and Patulin Production by Byssochlamys nivea in Apple Juice as Affected by Sorbate, Benzoate, SO2 and Temperature

The effects of potassium sorbate, sodium benzoate, SO₂ and incubation temperature on biomass and patulin production by Byssochlamys nivea in apple juice were determined. Growth at 21, 30 and 37°C over a 25-day incubation period was significantly retarded by 75 ppm SO₂, 150 ppm potassium sorbate and 500 ppm sodium benzoate. Biomass accumulated to approximately 500 mg/100 ml in control samples of apple juice. Patulin was produced in the highest concentrations at 21°C after 20 days incubation. After reaching a maximum concentration at 30 and 37°C, a rapid decline in patulin content was observed. Patulin production was also observed at 12°C. On the basis of concentration, SO₂ had the most significant effect on the rate of biomass and patulin production by B. nivea followed by potassium sorbate and sodium benzoate, respectively.     

Rheological Behaviour of an Insoluble Lemon Fibre as Affected by Stirring, Temperature, Time and Storage

In this work, the effect the preparation method (two different stirring systems at two temperatures and times), fibre concentration (between 2% and 3%), temperature (between 10 °C and 50 °C) and storage time (between 24 h and 50 days at 5 °C) had on the flow properties of a suspension of dietary lemon fibre prepared with a 45° Brix sucrose solution were evaluated. This information will be helpful in order to discover the best possibilities of using fibre to increase the viscosity of certain kinds of products, depending on the processing, storage and consumption conditions. The obtained results indicate that all the aspects which contribute to increase component solubilisation and the interaction of the insoluble fraction with the aqueous phase when preparing the suspension, such as a decrease in particle size, a rise in temperature or a longer homogenization time, entail a higher apparent viscosity. Moreover, favoring the solubilisation in the preparation process leads to a more stable rheological behaviour of the suspension during storage. As expected, the apparent viscosity of suspensions was dependent on the shear rate, concentration and temperature. A thixotropic behaviour of fibre suspension was only observed at a very low shear rate (5 s⁻¹).     

Preservative and Temperature Effect on Growth of Three Varieties of the Heat-Resistant Mold, Neosartorya fischeri, as Measured by an Impedimetric Method

The combined effects of inoculum amount, temperature, pH, and food preservatives on growth of three varieties of heat-resistant mold Neosartorya fischeri cultured on a fruit juice-like medium was investigated. JV. fischeri var. glabra growth occurred at 100 mg sodium benzoate/L at pH 3.5, a level that completely inhibited outgrowth of the other varieties. All were similarly affected by sulfur dioxide; completely inhibited by 300 mg/L at pH 3.5. The inhibitory effect of preservatives was strongly affected by pH, inoculum amount, and temperature. Growth was significantly delayed when temperature was decreased from 32 to 25 to 18°C or pH from 4.5 to 3.5. This is the first report on the use of impedance microbiology to study the effects of environmental factors on molds.