Pyrazines in extruded malt

Green malt, partially dried, was processed by high-temperature short-time (HTST) extrusion cooking at three different temperatures. Volatile components of the product were analysed by gas chromatography (g.c.) using a headspace sampling technique, and identified by mass spectrometry (m.s.). The concentration of pyrazines increased when the temperature was increased from 130 to 160°C, but it fell at 190°C, probably as an effect of volatilisation. However, the influence of parameters such as water content, the milling of the raw material and its residence time in the extruder must also be taken into account. Extruded malt contained more total pyrazines than conventionally processed malt. 2-Vinyl-5-methylpyrazine and 2-vinyl-6-methylpyrazine were found only in extruded malt, especially at high processing temperature. The pyrazine content per colour unit was high, an observation which may lead to the production of a more flavourful beer of the lager-type.     

Effect of steaming time on the linear expansion of fish crackers (‘keropok’)

The effect of steaming time on ‘keropok’ was studied. The morphology of the starch granules in keropok gel at different steaming times was examined using scanning electron microscopy (SEM). There was an optimum time for the steaming of keropok which gave the best linear expansion and hardest texture of steamed gel. This occurred when the starch granules were expanded to their largest sizes and before fragmentation of the granules. A steaming time of 20–30 min is sufficient to cook the keropok gel. Excessive steaming time will result in a poor-quality product as well as extra production costs. © 1999 Society of Chemical Industry     

膨化小米粉对挂面加工特性的影响

为充分利用小米杂粮资源,有效提高在面制品中的添加量,增加挂面的花色品种,本文将膨化小米粉按照一定比例添加到小麦粉中,对所得混合粉的粉质特性、拉伸特性、糊化特性进行了分析,同时对其混合粉制作的挂面品质进行了分析研究。结果表明:添加膨化小米粉可有效改善面团的粉质、拉伸和糊化特性;适量添加可有效降低挂面的最佳蒸煮时间,增强挂面的弹性和硬度。在该实验条件下,综合分析混合粉的粉质、拉伸特性和糊化特性,并通过测试分析挂面的蒸煮特性、断裂强度、熟挂面的剪切力等,最终确定挤压膨化小米粉最佳添加量为6%,为其在面制品中的应用提供了参考。      

Influence of food processing on iron availability in vitro from extruded maize-based snack foods

Samples of an extruded maize-based snack food taken at various points during manufacture were digested in vitro under simulated physiological conditions. The proportion of iron diffusing across a semi-permeable membrane was used as an index of bioavailability. Iron diffusibility increased from less than 3 % in raw whole maize to over 20 % in the finished product. Four processing stages were found to be responsible for this enhancement: (I) refining of raw maize, (2) product formulation, (3) extrusion cooking, (4) addition of flavourings. The extrusion cooking process itself was responsible for only a small part of the increase in iron diffusibility. There was a reduction in iron content due to refining, but a small increase in iron content due to product formulation and extrusion cooking. The various factors associated with each stage of snack food manufacture are discussed in relation to their potential influence on iron availability.     

氯化钠添加量对香酥鱼片制备工艺及产品品质的影响

以粘度、质构、色差及产品膨化度为评价指标,结合扫描电镜观察,研究盐含量对香酥鱼片制备工艺及产品品质的影响。实验结果表明,在氯化钠添加量为0%～4%内,随着氯化钠含量增加,鱼浆粘度增加,鱼糕白度增加,质构变化显著,且产品膨化度增加。通过分别添加低钠盐、氯化钾及氯化钙,比较口味及膨化度实验,发现添加4%低钠盐可使产品获得高膨化度,且咸度适宜。      

Effect of fish,starch and salt contents on the microstructure and expansion of fish crackers (‘keropok’)

Light microscopy studies on the fish cracker gel and expanded product (‘keropok’) emphasised the role of fish proteins in the starch expansion process. The addition of salt (20 g kg⁻¹) in the ‘keropok’ helped to distribute evenly the starch in the fish protein. Formation of thin fish muscle bundles assisted the expansion of ‘keropok’. At 700–900 g kg⁻¹ fish content, the fish muscle bundles formed a continuous network that caused a drop in the ‘keropok’ expansion. From the scanning electron microscopy study, ridges were found in samples (containing 600–900 g kg⁻¹ fish content) with 20 g kg⁻¹ salt at high magnification. © 1999 Society of Chemical Industry     

Micronised-roasted coffee from unripe fruits improves bioactive compounds and fibre contents in rice extruded breakfast cereals

Unripe green coffee is one of the by-products from coffee processing that does not have many applications in higher value-added food products. This study aimed to evaluate the chemical, technological, and sensory properties of rice-based breakfast cereal made with micronised-roasted coffee (MRC) from green coffee fruits. The products were elaborated with different MRC concentrations (2, 5 and 9%) and manufactured in a single screw extruder. Data were analysed by analysis of variance and Tukey's test (p < 0.05). The increase in MRC concentration improved the contents of caffeine, chlorogenic and caffeic acids in the breakfast cereals, and reduced the luminosity and expansion index due to the presence of brown colour and fibres from coffee beans. The cereal made with 5% of MRC was more accepted by consumers. Thus, MRC has proven to be a potential source of bioactive compounds, fibres and natural brownish colour for breakfast cereals.     

Effect on protein digestibility of different processing conditions in the production of fish meal and fish feed

The effect of processing conditions on protein digestibility and fluorodinitrobenzene (FDNB)‐reactive (available) lysine in the production of fish meal and extruded fish feed has been studied under pilot and commercial conditions using mink as model animals. Fish meal produced under pilot‐plant conditions at processing temperatures below 70–80 °C (FM1) had protein digestibility of 929 (grams of protein digested per 1000 g protein consumed) compared with 905 when processed at temperatures above 100 °C (FM2). A low‐temperature‐processed commercial fish meal (CFM1) had protein digestibility of 940 compared with 888 for a standard commercial fish meal (CFM2). Pilot‐produced extruded fish feed had protein digestibility of 913 when based on FM1 as the main protein source (95% of total protein) compared with 892 when based on FM2. Commercial extruded fish feed had protein digestibility of 912 when based on CFM1 compared with 871 when based on CFM2. Varying extrusion conditions at the pilot scale, ie temperatures from 100 to 126 °C and moisture contents from 21 to 12%, did not affect protein digestibility. Similarly, under commercial conditions, variation in temperature from 89 to 110 °C and moisture from 24.5 to 19.5% did not affect FDNB‐reactive lysine and protein digestibility. The FDNB‐reactive lysine content and protein digestibility of the extruded feed were less than the values calculated from the ingredient mixture before extrusion. Thus, despite different extrusion conditions not giving different FDNB‐reactive lysine and protein digestibility, the total process, ie extrusion, drying and oil coating, caused a reduction. Copyright © 2003 Society of Chemical Industry     

Selected properties of native or modified maize starch/soy protein mixtures extruded at varying screw speed

Mixtures of soy protein isolate and native or modified (crosslinked) maize starch were extruded in a twin‐screw extruder at screw speeds of 80, 120 and 160 rpm and a moisture content of 250 g kg^?1 (dry basis). Increasing screw speed did not affect the specific mechanical energy and water solubility and absorption indices but did affect the sectional expansion index and bulk density, as the flow rate of the feed was not held constant during extrusion. The sectional expansion indices of modified starch/soy protein mixtures were higher than those of native starch/soy protein mixtures, suggesting an effect of feed material in addition to phase transition on the expansion of extrudates containing soybean. Since the bulk densities of modified starch/soy protein mixtures were lower than those of native starch/soy protein mixtures, it appears that bulk densities of extrudates containing high percentages of soy protein can be reduced by the presence of crosslinked starch in the feed. Copyright © 2005 Society of Chemical Industry     

The effect of rice bran on physicochemical,textural and glycaemic properties of ready-to-eat extruded corn snacks

In this work, corn extruded snack products were enriched with rice bran (RB) at 10% and 15%. A co-rotating twin-screw extruder was used with a feed moisture content of 16 g 100 g⁻¹, a screw speed of 240 r.p.m. and four heating sections of the barrel (100, 140, 150 and 150 °C). The impact of RB inclusion on nutritional profile, starch digestion, physicochemical and textural properties of snack products was evaluated. RB-enriched extrudates showed a lower specific volume and hardness and higher crispness than control. RB at 15% gave a water-holding capacity lower than control. Rheology of extrudate dispersions indicated an increase in elastic interactions and solid-like behaviour with RB supplementation. Differences in rheological properties resulted in attenuation of predictive glycaemic response for RB-enriched snacks.     

Corn Grits Particle Size and Distribution Effects on the Characteristics of Expanded Extrudates

The effects of corn particle size and distribution on the ex trusion-cooking process was studied. Extrusion cooking was carried out in a twin-screw corotating extruder. The effects of particle characteristics were studied by analyzing process responses on-line, by expansion indices, mechanical (puncture test) and structural (computerized image analysis) prop erties of the extrudate. An increase in particle size for a given biochemical composition gave extrudates that were harder, with a modified expansion and lower cell density. The par ticle size distribution in the range studied was not significant. Correlations were found between expansion indices and process responses.     

Effect of tertiarybutylhydroquinone on lipid oxidation in fish crackers

The effect of tertiarybutylhydroquinone (TBHQ) in retarding lipid oxidation in fish crackers fried in refined, bleached and deodorised palm olein (RBD olein) during storage was evaluated. The indices of lipid oxidation used were the peroxide and p-anisidine values and u.v. absorbances at 232 and 268 nm of oil extracted from fish crackers stored at 60°C. Two methods for TBHQ incorporation into the fish crackers were used. Fish crackers that were prepared by frying of fish chips in RBD olein containing TBHQ were more stable towards oxidative rancidity than control fish crackers prepared with RBD olein without TBHQ. The rate of lipid oxidation in fish crackers prepared from fish chips that were made with TBHQ in the dough formulation and fried in RBD olein without TBHQ was slightly higher than in control fish crackers. A storage study carried out at room temperature (30°C) showed the same trend in relative rates of lipid oxidation. The study showed that the incorporation of TBHQ into the frying medium was an effective means of retarding the onset of rancidity in fried fish crackers while the incorporation of TBHQ into the dough mixture made the fish cracker slightly more susceptible towards lipid oxidative reactions.     

不同熟化工艺处理对谷物杂粮果蔬粉品质的影响

研究了谷物杂粮经过不同的熟化工艺(烘炒工艺、挤压膨化工艺、蒸煮工艺)后对谷物杂粮果蔬粉营养成分、色泽、流动性、吸水率、结块率以及感官品质的影响。研究发现加工工艺对谷物杂粮果蔬粉营养影响较小,烘炒工艺加工的谷物杂粮果蔬粉在色泽、流动性、结块率以及感官品质方面明显优于其他两种工艺。     

Development of extruded snacks using jatobá (Hymenaea stigonocarpaMart) flour and cassava starch blends

The use of the jatobá trees (Hymenaea stigonocarpa Mart) by the timber industry poses an ecological problem in Brazil. The objective of this research was to investigate the use of jatobá flour for the production of snacks by the thermoplastic extrusion of a composite flour consisting of jatobá and cassava starch. Chemical analysis showed that the jatobá fruit provides high-fibre flour (486 g kg⁻¹) with 66 g kg⁻¹ protein, and 398 and 88 g kg⁻¹ of insoluble and soluble fibre, respectively. Such flour is of potential use for the production of high-fibre snacks, allowing for the economical exploitation of the jatobá while preserving the tree. Composite flours with jatobá flour and cassava starch mixtures (150: 850, 300: 700, 450: 550), conditioned to moisture levels of 170, 200 and 230 g kg⁻¹ were processed in a Brabender single-screw extruder. The extrusion conditions were 150 rpm screw speed, 4 mm die diameter and 125, 150 and 175°C of barrel temperatures. The snacks produced were evaluated as to their sensory characteristics and response surface methodology was used to optimise the extrusion process. Response surface and contour diagrams revealed that all mixtures conditioned to 170 g kg⁻¹ moisture and extruded at 150°C produced snacks of acceptable quality, higher levels of jatobá flour leading to significant quality losses with respect to sensory characteristics. © 1998 Society of Chemical Industry.     

Reduction of fumonisin B1 in extruded corn breakfast cereals with salt,malt and sugar in their formulation

The objective was to determine the effect of added sodium chloride, barley malt and sucrose on the stability of fumonisin B₁ (FB₁) present in corn flour. Two levels of both sodium chloride (0.4% and 2%) and barley malt (0.8% and 5%) were added to the unextruded corn flour, and six levels of sucrose (3–10%) were used. The addition of sucrose at the lowest salt content (0.4%) as well as salt, either at 0.4% or at 2%, led to a significant decrease of FB₁ levels in extruded samples, whereas malt, either at 0.8% or at 5%, did not significantly affect FB₁ stability. Decontamination rates depended on the concentrations of added ingredients and ranged from 2% to 92%. The greatest reductions in FB₁ content were achieved with extrusion cooking with a high salt content, whilst the lowest reductions were the result of processing corn flour with low contents of both salt and sucrose. Salt at 2% was the most effective ingredient in reducing FB₁ content of the final extruded food.     

Screw Configuration Effects on Corn Starch Expansion During Extrusion

Normal corn starch was extrusion cooked in a Brabender single-screw extruder. Three screws with no mixing, one mixing or two mixing elements were used to extrude the samples through a 3 mm cylindrical die nozzle at 140°C barrel temperature and 140 rpm screw speed. Dependent variables included overall and radial expansion ratios, bulk density and specific mechanical energy (SME). Extrudates were ground and re-extruded using the same three screws, and the same extrusion conditions. Significant differences (P < 0.05) in bulk density, SME and radial expansion ratio were found on re-extrusion. No changes occurred in overall expansion ratio (P < 0.05).     

Using fish gelatin and pectin to make a low-fat spread

This preliminary work involved the characterization of a low-fat spread made of fish gelatin and pectin with or without salt addition and pH adjustment. The samples prepared were characterized by temperature sweep, bulk density determination, texture analysis and morphology evaluation. It was found that a decrease in fish gelatin to pectin ratio resulted in an increase in bulk density, firmness, compressibility, adhesiveness, elasticity and melt ability. In addition, spreads prepared at high acidity gave rise to syneresis, which could be remedied with addition of sodium chloride.