Effects of Microwave Drying on Lipid Oxidation of Stuffed Pasta

The aim of this work was to evaluate and compare the effects of conventional (hot air) and microwave drying on the lipid oxidation of stuffed pasta. Experiments were carried out on the pasta type ravioli dried by conventional and microwave treatments. Peroxide values and induction times were evaluated for the oil extracted from the stuffing. Peroxide values of the lipid extracts for the samples dried by conventional drying and microwave drying were similar (P-level = 0.51) and less than threshold acceptable value (25 mequiv O₂/kg oil). The use of microwave processing could be a remarkable energy saving measure as well as a way of lowering production costs without compromising product quality.     

休闲豆干真空脉冲卤制工艺优化

本文以休闲豆干为原料,通过单因素实验方法,明确卤制温度、卤制时间、真空度对休闲卤豆干的感官评分的影响。按照Box-Behnken设计试验方案,运用响应面分析法建立二阶多项非线性回归方程和数据模型,以感官评分为指标,优化休闲豆干真空脉冲卤制工艺,确定卤制温度、卤制时间、真空度。再结合脉冲次数分析研究,得到最佳脉冲次数。结果表明,休闲豆干真空脉冲卤制工艺的最佳工艺条件为:卤制温度80 ℃,卤制时间80 min,真空度0.03 MPa,脉冲次数为3,在此条件下的豆干感官评分为(89.80±1.33)分。真空脉冲卤制与传统卤制相比,缩短了卤制时间,提高了生产效率、保留了食品风味,降低了感染微生物的风险,产品安全性大幅提升。     

DYNAMIC VISCOELASTIC PROPERTIES OF PASTA AS A FUNCTION OF TEMPERATURE AND WATER CONTENT*

Pasta samples were tested in the linear viscoelasticity range using a dynamic mechanical thermal analyzer over the temperature range of 25 to 95C and the water content range of 12 to 20% (weight of water/weight of solids). To obtain wholesome pasta samples at different moisture levels, the intermittent sorption technique was used. The behavior of G′ and tanδversus temperature curves exhibited a transition, which was determined to be the glass transition by making comparisons to the literature values of glass transition for starch and semolina extrudates. At 12.5% water content, glass transition initiated at 48.7C. With increase in water content values, the initiating glass transition temperature decreased. At 19.7% water content, glass transition was observed in the temperature range of 36.9 to 57.3C. Although pasta contains about 13% protein fraction, it did not seem to affect the major part of glass transition range because the pasta proteins become mobile at temperatures greater than 80C and water content greater than 17%.     

果蔬干制品加工过程中对微生物的控制及其灭菌工艺的研究

食品中微生物含量的控制对延长食品保质期,减少食品营养成分损失,保障食品安全具有非常重要意义。本文综述了果蔬干制品加工过程中微生物的主要来源以及在果蔬干制品生产制造过程各个环节中微生物的防治方法,并对果蔬干制品生产中常见的杀菌方式及其杀菌效果进行了概述。对今后果蔬干制品生产加工过程中微生物的防控及其杀菌方式具有理论指导意义。     

Effect of cassava starch gel,fish gel and mixed gels and thermal treatment on structure development and various quality parameters in microwave vacuum-dried gel slices

Three types of gels including tapioca starch gel, fish gel and mixed gels of both (cassava starch: fish = 1:1) were prepared under different thermal conditions. Slices (4 mm thick) derived from these the gels were dehydrated to a final moisture content of 7% in a microwave vacuum dryer. The micro/macro structure and selected quality parameters of the dried gel chips were measured e.g. shape, relative volume, bulk density, texture, color, sensory and microstructure. The measured gel characteristics were analyzed and related to structure development and selected quality attributes. Both fish and mixed gel chips expanded in both diameter and thickness while the starch gel chips shrank in diameter, but expanded in thickness; the former two represented a continuous cross-section composed of a cellular structure and expanded uniformly in thickness while the latter developed an open cross-section and the center expanded more than the edge region, indicative of a disc and pillow shape, respectively. The higher severity of thermal treatment favored greater expansion and reduced hardness and bulk density, and increased crispness in the mixed gel chips; they developed a smooth and fine surface and pore wall but decreased lightness and whiteness due to starch gelatinization in the starch and mixed gel chips. Only the partial dried mixed gel chips are acceptable to the panelists. A homogenous co-gel in the mixed gel contributed to the higher uniform expansion and cellular structure. These findings will help developing the restructured microwave vacuum-dried product by blending the starch with the fish.     

Utilisation of beef lung protein powder as a functional ingredient to enhance protein and iron content of fresh pasta

Beef lungs are an underutilised co-product of the meat industry that could be used as an ingredient to supplement the protein content of cereal foods. Beef lung powder (BLP) had a protein content of 87% (dry weight basis), an amino acid score of 1, and contained 1 mg g⁻¹ iron. Fresh semolina pasta was used as a model food, and BLP was incorporated up to 20%. Incorporation of 10% BLP improved the indispensable amino acid score of the pasta from 0.48 to 0.91. At that level of incorporation, higher cooking loss and redder (increased ‘a’ value) and darker (decreased ‘L’ value) colour resulted. The fresh pasta with BLP had a lower glycaemic response compared to control samples. BLP improved the functional value of the fresh pasta and is a potential ingredient in the development of new food products.     

Ingredient composition and pasta:water cooking ratio affect cooking properties of nontraditional spaghetti

An experiment was conducted to determine the effect of different pasta:water ratios and nontraditional ingredients on the cooking properties of spaghetti. Spaghetti was made using semolina and semolina containing 20% (w/w) nontraditional (NT) ingredients (corn, flaxseed, lentil, oat, pinto bean and soybean flours). Pasta:water ratios evaluated were 13 g:400 mL, 27 g:400 mL and 48 g:400 mL. Addition of pasta caused a decline in cooking water temperature. The water temperature drop and recovery time to boiling (100 °C) varied with pasta:water ratio and with nontraditional ingredient in the spaghetti. These results were attributed to the calculated specific heat capacity of the ingredients incorporated in the spaghetti. Cooking time was reduced for all NT spaghetti with respect to the control sample and was longest when 48 g of pasta was cooked. Pasta:water ratio affected cooking loss but not cooked weight or cooked firmness. Cooking losses were greater with 13 g:400 mL compared to 48 g:400 mL.     

The impact of the protein network on the pasting and cooking properties of dry pasta products

Durum wheat semolina gluten and starch as well as processing conditions determine pasta cooking quality. This study investigated whether, for good organoleptic properties, a permanent protein network needs to be formed during pasta drying or can still be formed during cooking. The cooking quality of 16 spaghetti samples was related to the levels of sodium dodecyl sulphate extractable protein (SDSEP), starch gelatinisation temperatures as well as to the swelling properties of milled dry spaghettis. SDSEP levels in dry and cooked products varied between 31% and 56%, and 12% to 21% of total protein contents, respectively. The highest quality spaghettis had relatively higher levels of SDSEP in the dry product, low starch gelatinisation temperatures and swelling powers, and rigid particles. The lowest quality spaghettis had lower levels of SDSEP and higher gelatinisation temperatures. This work implies that high pasta quality results from an optimal degree of protein polymerisation during drying and/or the subsequent cooking.     

Mathematical Modeling of the Coupled Transport Phenomena and Color Development: Finish Drying of Trellis-Dried Sultanas

A mathematical model for simulation of simultaneous heat and mass transport was developed to describe the drying kinetics during finish drying of trellis-dried sultanas. In this model, the governing partial differential equations for heat and mass transfer for a solid spherical body were numerically solved using a finite difference technique. In addition, a kinetic model was coupled to the heat and mass transfer calculations to simultaneously predict the evolution of product color during the drying process. This allows predictions of moisture content, temperature, and color profiles of the product in a space–time domain during the drying process as a function of various operating conditions.

Predictions compared well with the experimental values, implying that the proposed numerical model can be used with confidence for the simulation of the important transport phenomena in optimizing the design and operation of a drying system for sultanas that maximizes the retention of the desired product color. The work has demonstrated the importance of establishing optimal and closely controlled drying conditions because significant effects of the key operational parameters on drying kinetics and the associated changes of product color were found. The modeling approach proposed here can be extended to other products and for incorporation of other product quality indices.     

The microbiological safety of ready-to-eat specialty meats from markets and specialty food shops: A UK wide study with a focus on Salmonella and Listeria monocytogenes

From 2359 specialty meats (continental sausages, cured/fermented, dried meats) sampled from markets and specialty food shops, 98.9% of samples were of satisfactory or acceptable microbiological quality. However, 16 (0.7%) were unsatisfactory as a result of Escherichia coli, Staphylococcus aureus or Listeria spp. contamination (≥10² CFU/g), and nine (0.4%) were unacceptable due to presence of Salmonella spp. or Listeria monocytogenes (>10² CFU/g). Meats with unacceptable levels of L. monocytogenes were within shelf life (range: 8–143 days remaining). Nine different subtypes of L. monocytogenes were detected with sero/AFLP type 1/2c VII predominating (37%), although this subtype was not overrepresented in any particular meat type (P > 0.05). Ninety-six percent of continental sausages and cured/fermented products were stored at <8 °C at premises, including seven of the nine unacceptable samples. These nine meats were all pre-packed prior to supply to retail premises (OR = 0.1 P = 0.003) indicating that contamination with bacterial pathogens occurred earlier in the production chain. Most samples (72.7%, 8/11) with unsatisfactory levels of E. coli were sliced on request, suggesting cross-contamination at point of sale. This study highlights the importance of ensuring that products do not become contaminated before final packaging, that storage conditions are controlled, and that durability dates are an accurate indication of the shelf life of the product so as to minimise the potential for L. monocytogenes to be present at levels hazardous to health at the point of sale.