Process dynamics of starch-based microcellular foams produced by supercritical fluid extrusion. I: model development

Supercritical fluid extrusion (SCFX) has been used successfully to produce biopolymeric foams with bubble size in the range of 50–200 microns, and bubble density to the order of 10⁶ per cm³. Final bubble size and expansion ratio of extrudates depend on process and material parameters like CO₂ injection rate, nozzle temperature, oven temperature, melt viscosity, melt yield stress, etc. The objective of this study was to describe SCFX process dynamics and post-extrusion drying mechanism by using a mathematical model for bubble growth at the microscopic level in conjunction with a macroscopic model for flow of starch melt through the extruder nozzle, bulk diffusion of CO₂ and water to the atmosphere and heat transfer in the extrudate. The model was written in Visual Basic. The model provided the basis for a good understanding of the mechanisms of bubble growth and collapse, post-extrusion drying and open cell formation during SCFX processing, and is the only such one developed so far for extrusion puffed products. Simulation results and comparison with experimental data are presented in Part II of this paper.     

Development of a Method for Manufacturing Noodles from Finger Millet

Available methods of preparing foods from finger millet at home are laborious, time consuming, and people are reluctant to prepare foods from finger millet even though finger millet is a nutritionally important food item. Also, there are hardly any food items prepared from finger millet in the market, and less attention has been given to finger millet. As a solution for this problem, a study was carried out to develop a medium scale method for manufacturing of noodles from finger millet with maximum substitution, and tests were conducted by using a process line used to manufacture rice noodles with modifications. Based on the results of the preliminary experiments, main tests were carried out with blending ratios of finger millet to rice flour percentages of 50:50 and 100:0 with three replicates. Flours were mixed with water to increase the moisture content up to 35% and pellets were formed. Paste prepared by steaming the pellets was extruded to make sheets, and they were sent to an extruder to form noodles. Formed noodles were sterilized at 100⁰C, cut to 4 inches length pieces and sent to a dryer. Temperature of drying air was maintained about 40-45⁰C. It was found that the moisture content and percentage total solids in gruel of both types of produced noodles were satisfied the maximum allowable level for rice noodles i.e.12% and 8% according to SLS 858. Sensory evaluation results revealed that both types of noodles produced with finger millet were highly acceptable and 100% finger millet noodles were shown a higher acceptability in colour than 50% finger millet noodles. Developed finger millet noodles packed in PET/LDPE bags can be stored more than 1.5 years without any deterioration of quality. Hence, the developed method can be used to manufacture 100% finger millet noodles commercially on a medium scale level. Cost of production is 250 SLR per kg.     

营养冲调粥流化床干燥特性及动力学模型的建立

利用流化床干燥装置,对营养冲调粥（玉米、红豆、荞麦、燕麦和小米质量比为3.5∶3.0∶2.0∶0.7∶0.8,加水后经双螺杆挤压膨化制得）的流化床干燥特性进行实验研究,探讨干燥过程中不同风速、进风温度以及产品加工过程中的加水量对营养冲调粥干基水分质量分数和干燥速率的影响,得到了营养冲调粥流化床干燥的失水特性规律。根据实验数据建立营养冲调粥流化床干燥的动力学模型,并对模型进行统计检验。结果表明,经拟合得到营养冲调粥流化床干燥的最佳模型为Page模型,拟合方程为：ln（－ln MR）＝－4.064 63＋0.014 14T＋0.069 85v＋0.327 5H＋（0.570 96＋0.000 976 25T－0.009 68v－0.265 5H）ln t（T为进风温度/℃;v为干燥风速/（m/s）;H为原料加水量/%）,此方程能够较好地描述营养冲调粥的干燥过程,准确预测各阶段营养冲调粥的干基水分质量分数和干燥速率。     

Couscous, a traditional Turkish food product: production method and some applications for enrichment of nutritional value

Traditional Turkish couscous, a cereal‐based product, is made by covering bulgur with milk and flour. Traditionally Turkish couscous was produced from different flours (soyflour and oat flour) and eggs. The nutrient composition of traditional couscous was 90.6% dry matter, 11.27% protein, 2.58% fat, 71.80% carbohydrate, 42.25 mg sodium, 365.62 mg potassium, 2.73 mg iron and 48.30 mg calcium. The calorie content of traditional couscous is about 1487.41 kJ 100 g^?1. The addition of soy and oat flours increased protein content and Ca, K and Fe levels. Sensory properties were also affected. Panellists preferred traditional couscous and couscous with eggs or soyflour over couscous with oat flour.     

The functional properties of popped, flaked, extruded and roller-dried foxtail millet (Setaria italica)

Foxtail millet grains were decorticated in rice‐milling machinery and the decorticated millet was processed to prepare flaked, extrusion cooked and roller‐dried products, whereas the native grains were subjected to high‐temperature, short‐time treatment to prepare popped millet. The nutrient composition and some of the functional properties of the products were determined, principally solubility and swelling power in water, oil absorption capacity and pasting characteristics. Carbohydrate and lipid profiles of the products were also studied. The changes in the starch granular structure caused by heat treatment were examined by scanning electron microscopy. The degree of starch gelatinization was highest in the case of roller‐dried millet followed by popped, flaked and extruded products. It was concluded that the cereal processing technologies that were investigated could be successfully applied to foxtail millet to prepare ready‐to‐eat or use products, thereby increasing its utilization as a food.     

Influence of depigmentation of pearl millet (Pennisetum gluacum L.) on sensory attributes, nutrient composition and in vitro digestibility of biscuits

Presence of high concentration of pigments in the pericarp and endosperm regions of pearl millet imparts undesirable gray color to its products. This study attempts to improve the acceptability of pearl millet products through processing technique and to study its effect on nutritional composition of pearl millet product. Pearl millet grains were depigmented by soaking in 0.2 N HCl for 18 h followed by washing, blanching at 98°C for 30 s and sun drying. Three different types of biscuits were prepared from refined flour (Reference), native or unprocessed pearl millet (T-I) and depigmented pearl millet (T-II). Results indicated that depigmentation improved the sensory attributes especially the color of pearl millet biscuits (T-II). The protein, fat, ash and total dietary fiber of pearl millet based biscuits (T-I as well as T-II) were significantly (P?0.05) higher than the reference biscuits. Depigmentation significantly improved the in vitro starch digestibility, in vitro protein digestibility and the soluble dietary fiber content of pearl millet biscuits (T-II) by 14.50, 6.56 and 6.18%, respectively. On the other hand, a significant decrease of 6.73, 2.43 and 17.03 g/100 g in protein, starch and insoluble dietary fiber was detected in pearl millet biscuits (T-II) due to depigmentation.     

不同干燥方法对速食小米粉品质及体外抗氧化活性的影响

采用微波真空干燥（Microwave vacuum drying,MVD）、微波热风干燥（Microwave hot air drying,MHAD）、热风干燥（Hot air drying,HAD）和传统烤制法（Traditional roasting,TR）4种干燥方法制备高品质纯天然速食小米粉,比较了4种干燥方法对速食小米粉营养成分、粉体特性和抗氧化活性的影响。结果表明:与生小米粉相比,干燥后的小米粉营养成分含量和体外抗氧化活性能力均下降,粉体特性增强。其中MHAD法制备的小米粉粗脂肪、蛋白质和多酚含量最高,分别为2.64、8.63、57.2 g/100 g,清除DPPH自由基、超氧阴离子和还原力能力最高,其IC₅₀分别为0.138和0.134 mg/mL,还原力为1.98,粉体具有最好的流动性,吸湿性最低（39.34%）,结块度最低（17.01%）,碘蓝值最高（0.685）,并获得最高的感官评价分（95.2分）。MVD法制备的小米粉黄色素含量最高（67.22 mg/100 g）,清除羟自由基的能力最强（IC₅₀为0.059 mg/mL）。综合比较,微波热风干燥法在速食小米粉制备中能较完整地保持其营养成分,品质好且抗氧化性强,可作为制备小米粉的适宜干燥新方法。     

广式腊肠干燥工艺改进切入点的初步确定

模拟广式腊肠工业化生产中热风干燥的工艺条件,探讨了水分、亚硝酸盐、氨基酸、游离脂肪、发色率等理化指标的变化规律。结果表明,在干燥的第1d,水分蒸发处于主导地位,其他反应相对不显著或者受水分蒸发影响小,而与产品风味密切相关的生化反应主要集中在第3d。初步确定,第1d的干燥过程可以作为工艺改进的切入点。     

熟化方式对小米粉制品挥发性成分的影响

用蒸煮和挤压膨化2种熟化方式制备小米粉,采用顶空固相微萃取法(HS-SPME)提取挥发性成分并与气相色谱-质谱(GC-MS)联用,分析了2种熟化方式制备的小米粉制品中挥发性成分。结果显示,蒸煮小米粉制品中主要有33种挥发性成分,膨化小米粉制品中主要有20种挥发性成分,其中含有15种相同挥发性成分。蒸煮小米粉制品和膨化小米粉制品都产生了较多的醛类化合物,是熟化小米粉制品中的主要挥发性风味物质,膨化小米粉制品中的不良风味的醛类化合物较少;蒸煮小米粉制品中检测到了较多的酮类化合物,而膨化小米粉制品中检测到较多的杂环类化合物。蒸煮小米粉制品中的挥发性风味物质的种类和含量要高于膨化小米粉制品。     

Dietary exposure to furan of the Austrian population

ABSTRACT

In the period from 2007 to 2017 furan levels of foods were analysed by the Austrian Agency for Health and Food Safety. Based on these analytical data and the Austrian consumption data the dietary exposure of children and adults to furan was estimated by using a deterministic approach. For the adult population the mean and 95^th percentile dietary exposures to furan were estimated at 0.31 µg/kg bodyweight per day and at 0.72 µg/kg bodyweight per day, respectively. The mean dietary exposure of children was estimated at 0.18 µg/kg bodyweight per day and is thus only about half as high as for Austrian adults. At the 95^th percentile the dietary exposure of children was estimated at 0.49 µg/kg bodyweight per day. The main contributor to the total dietary exposure for adults is coffee followed by convenience products and for children the main contributors are grain products as well as convenience products, bread and snacks. Based on the BMDL₁₀ of 0.064 mg/kg bodyweight per day for the development of cholangiofibrosis, the MOE-calculation revealed that the current levels of dietary exposure to furan are of concern for Austrian adult high consumers. The MOE-calculation, based on the BMDL₁₀ of 1.31 mg/kg bodyweight per day for the development of hepatocellular adenomas, indicated a health concern for Austrian children and adults.     

Effects of feed moisture and extruder screw speed and temperature on physical characteristics and antioxidant activity of extruded proso millet (Panicum miliaceum) flour

The objective of this work was to determine the impact of extrusion variables [moisture (17–25%), screw speed (170–250 r.p.m.) and temperature (90–150 °C)] on the physical properties and antioxidant activity of proso millet extrudates. Extrusion variables were adjusted using an inscribed central composite rotatable design. Response variables were bulk density (BD), radial expansion ratio, water absorption index, water solubility index, hardness, colour (L*, a*, b*) and antioxidant activity. Moisture and screw speed were the most influential variables affecting millet extrusion: their linear, quadratic and interaction terms accounted for more than 50% of the variability in all responses except for b*. Expansion was greatest at severe conditions of low moisture and high screw speed. These conditions were also consistent with the highest antioxidant activity. This study demonstrated that high expansion and antioxidant activity can be obtained by extruding proso millet under low moisture and high screw speed conditions.     

内蒙古锡盟地区传统肉制品的品质分析

研究结果表明,锡盟传统肉制品包括汽蒸类、烧烤类、油炸类、人工风干类、自然风干类、烘干类6大类;不同地区不同类型的传统肉制品均以体积小、水分质量分数18.6%～38.9%、蛋白质质量分数36.6%～54.8%、脂肪质量分数9.79%～13.9%、易携带,具有传统肉制品所特有的色泽和风味、呈现了良好的组织状态特点,自然风干类传统肉制品含水量低,口感较硬,不加任何添加剂,其他类型肉制品亚硝酸盐含量13～27mg/kg和食盐质量分数5.2%～7.9%;一些无包装产品或简单包装的产品存放过程细菌总数超标,霉菌和酵母菌开始生长,但大肠菌群数在标准范围内,未检测出致病菌金黄色葡萄球菌。     

The effect of extrusion temperature and drying-tempering on both the kinetics of hydration and the textural changes in extruded ready-to-eat breakfast cereals during soaking in semi-skimmed milk

Ready‐to‐eat breakfast cereals were made by a two‐step extrusion‐cooking and toasting process. Before toasting the products were given a drying‐tempering step. Two process variables (extrusion temperature and moisture content before toasting) were manipulated in order to obtain products with different physical characteristics. Density, hardness, hydration kinetics and textural changes of the products during soaking were studied in order to analyse the influence of these variables on the product quality. Both the variables significantly affected the product quality indices such as hardness and density. The processing conditions had only a slight influence on product water uptake during hydration but a dramatic influence on product softening. The hydration and softening rates were negatively correlated with density. When density was equal samples extruded at different extrusion temperatures showed different water uptake and softening rates. Products with the same values of initial hydration rate showed different initial softening rates because of extrusion temperature.     

The pasting behaviour of lactic‐fermented and dried uji (an East African sour porridge)

The effects of sun‐, cabinet‐, and drum‐drying on the behaviour of submerged culture lactic‐fermented pure cassava, maize and finger millet and composites of maize–finger millet and cassava–finger millet were investigated in a Brabender amylograph. The cereal flours and maize–finger millet composite had higher onset and peak gelatinization temperatures but lower peak viscosities than cassava or cassava–finger millet composites. Fermentation alone or in combination with drying increased the viscosity of the flours, except for the fermented and drum‐dried cassava–finger millet composite flour. This increased viscosity of uji on fermentation and drying makes it more difficult to cook. Fermented and drum‐dried flours recorded high initial viscosities, at 30 °C, when the amylograph was switched on. Copyright © 2003 Society of Chemical Industry     

Performance of Drying Technologies to Ensure Microbial Safety of Dried Fruits and Vegetables

Dried fruits, vegetables, herbs, and spices are produced in and sourced from many countries worldwide, but they have been increasingly reported to be involved in outbreaks and alerts due to the presence of foodborne pathogens such as Salmonella. These dried products are mainly produced by solar drying and conventional air drying, but a wide range of drying technologies are available. From a technological point of view the general trend is to optimize and standardize the drying process to ensure high‐quality products to be offered. Drying technologies are mainly evaluated for their performance to reduce water activity at low energy cost while maintaining good sensorial quality of the dried product. However, as low water activity foods are increasingly recognized to support microbial survival and dried products are often consumed as they are, or are used as ingredients in many ready‐to‐eat foods, there is increasing attention to the microbiological quality and safety aspects of these products. This review presents traditional and emerging technologies to dry fruits, vegetables, herbs, and spices and discusses their potential to inactivate bacteria and viruses throughout the drying process. Overall, the microbial inactivation effect of the presented technologies has not yet been thoroughly assessed, even for traditional methods like solar drying, conventional air drying, or freeze‐drying. Emerging technologies such as dielectric (assisted) drying and low‐pressure superheated steam drying have been shown to reduce microbial populations; however, the number of studies is still low. Very few studies have focused on viral inactivation during drying processes.     

小米挤压粉与小米生粉理化性质及营养品质的差异比较

为了全面分析挤压膨化处理对小米粉品质特征的影响,本文系统比较了小米挤压粉与小米生粉理化性质及营养品质的差异,结果发现:小米挤压粉的密度极显著低于小米生粉(P<0.01),而粒径(P<0.01)和静止角(P<0.01)极显著高于小米生粉。挤压膨化后,小米挤压粉亮度(L*)减小、色泽(a*)变暗、肉眼可观察到色泽的差异。挤压膨化过程中产生较多阈值较低,风味贡献较大的醛类、呋喃类和吡嗪类挥发性风味物质,使得小米挤压粉的风味明显优于小米生粉。醛类,尤其是己醛(其相对质量分数高达34.58%),是小米挤压粉的主要风味贡献物质。与小米生粉相比,小米挤压粉的干基脂肪含量和直链淀粉含量分别减少28.92%和28.21%,但多不饱和脂肪酸含量增加21.08%,其中亚油酸增加19.92%、亚麻酸增加63.40%。据此推测,适量添加小米挤压粉将有利于增强小米制品的风味、改善成品口感、提高成品质量。     

Energy analysis of a Kori-tofu plant

Consumption of energy was analysed on a Kori-tofu plant which processed 6 tons of soybeans per day, involving 13 operations such as wetmilling, extraction-denaturation of soy protein, coagulation, compression, freezing, thawing, drying and waste-water treatment. Total energy consumption per 1 kg of the dry Kori-tofu was 27·1 MJ of fuel energy (27·9 MJ of exergy) plus 8·3 MJ of electrical energy. Energy-intensive operations were the extraction-denaturation of soy protein and the drying for thermal energy, and the refrigeration and the waste-water treatment for electrical energy. The extraction-denaturation of soy protein consumed twice as much thermal energy as the drying. The waste-water treatment consumed more electrical energy than the whole manufacturing process. Points for energy conservation are discussed.     

Gluten contamination in oat products and products naturally free from gluten

Some countries now allow celiac patients to include oats in their gluten-free diet. Studies have shown that commercially available oats can be contaminated with gluten. The aim of the study was to analyse oat products and products naturally free from gluten to determine the degree of contamination. A total of 88 oat products and 22 products based on maize, rice, millet or buckwheat were analysed, using a commercially available enzyme-linked immunosorbent assay (ELISA) with a monoclonal antibody to gliadin. The ELISA is quantitative with a detection limit of 20 mg/kg gluten. Some of the positive samples were also analysed for the presence of DNA from wheat, barley or rye. Thirteen percent of the oat products had gluten content over 200 mg/kg. Of the products naturally free from gluten 14% had a gluten content over 200 mg/kg. There was a tendency for higher levels of contamination with increased processing. The risk of gluten contamination in oat products as well as in non-gluten cereals must be considered. The level of contamination was in most cases low. The results regarding oats can be compared to those of such cereals as maize, rice, buckwheat and millet.     

Image analysis for detecting insect fragments in semolina

Semolina is used for the manufacture of pasta (long goods and short goods) and couscous and any contrasting colored specks adversely affect the appearance of the finished product. The specks result from wheat bran, diseased wheat, ergot or weed seeds. However, there is also the possibility that insect fragments will appear as specks. Specks are currently mostly determined by a manual process or by a speck counter in milling units. We compared the speck counts from an electronic speck counter (SPX Maztech Micrco Vision), acid hydrolysis and flotation (AOAC method 993.26), and near-infrared (NIR) hyperspectral imaging in semolina seeded with insect fragments (50-300 fragments/50 g) of Tribolium castaneum (Coleoptera: Tenebrionidae). There was a significant positive correlation between the number of insect fragments added and detected by all three methods. These results underline the importance of controlling insects in flour mills producing semolina, and also in plants producing pasta and couscous, to reduce speck counts in the finished products.     

Agglomeration of food powder and applications

Agglomeration has many applications in food processing and major applications include easy flow table salt, dispersible milk powder and soup mix, instant chocolate mix, beverage powder, compacted cubes for nutritional-intervention program, health bars using expanded/puffed cereals, etc. The main purpose of agglomeration is to improve certain physical properties of food powders such as bulk density, flowability, dispersability, and stability. Agglomerated products are easy to use by the consumers and hence are preferred over the traditional non-agglomerated products that are usually non-flowable in nature. The properties of food agglomerates and the process of agglomeration like employing pressure, extrusion, rewetting, spray-bed drying, steam jet, heat/sintering, and binders have been reviewed. The physical and instant properties of agglomerated food products have also been discussed.