A Controlled Agitation Process for Improving Quality of Canned Green Beans during Agitation Thermal Processing

This work introduces the concept of a controlled agitation thermal process to reduce quality damage in liquid‐particulate products during agitation thermal processing. Reciprocating agitation thermal processing (RA‐TP) was used as the agitation thermal process. In order to reduce the impact of agitation, a new concept of “stopping agitations after sufficient development of cold‐spot temperature” was proposed. Green beans were processed in No. 2 (307×409) cans filled with liquids of various consistency (0% to 2% CMC) at various frequencies (1 to 3 Hz) of RA‐TP using a full‐factorial design and heat penetration results were collected. Corresponding operator's process time to impart a 10‐min process lethality (F_o) and agitation time (AT) were calculated using heat penetration results. Accordingly, products were processed again by stopping agitations as per 3 agitation regimes, namely; full time agitation, equilibration time agitation, and partial time agitation. Processed products were photographed and tested for visual quality, color, texture, breakage of green beans, turbidity, and percentage of insoluble solids in can liquid. Results showed that stopping agitations after sufficient development of cold‐spot temperatures is an effective way of reducing product damages caused by agitation (for example, breakage of beans and its leaching into liquid). Agitations till one‐log temperature difference gave best color, texture and visual product quality for low‐viscosity liquid‐particulate mixture and extended agitations till equilibration time was best for high‐viscosity products. Thus, it was shown that a controlled agitation thermal process is more effective in obtaining high product quality as compared to a regular agitation thermal process.     

Kinetic Parameter Estimation for Quality Change during Continuous Thermal Processing of Grapefruit Juice

Reaction order, activation energy (E_a) and average rate constant (k_av) were evaluated by dynamic modeling for color degradation of grapefruit juice during thermal processing. Simulated aseptic conditions were: 85–135°C, 40–175 set processing time, and average velocities 5–30 cm/set. Quality was assessed by nonenzymatic browning index (NEBI) and S-hydroxymethyl-furfural (HMF). Average values for reaction-order and energy of activation were: 0 and 21.4 kcal/g-mol (NEBI) and 0.3 and 23.2 kcal/g-mol (HMF), respectively. These values were compared with those contained in the deformed ellipsoid which define the 90% joint confidence interval of all possible parameter combinations. Based on initial and final concentrations, the method can predict effects of processing on liquid foods.     

Multiobjective Optimization Approach: Thermal Food Processing

ABSTRACT:  The objective of this study was to utilize a multiobjective optimization technique for the thermal sterilization of packaged foods. The multiobjective optimization approach used in this study is based on the optimization of well-known aggregating functions by an adaptive random search algorithm. The applicability of the proposed approach was illustrated by solving widely used multiobjective test problems taken from the literature. The numerical results obtained for the multiobjective test problems and for the thermal processing problem show that the proposed approach can be effectively used for solving multiobjective optimization problems arising in the food engineering field.     

Sodium Chloride Diffusion in Low‐Acid Foods during Thermal Processing and Storage

This study aimed at modeling sodium chloride (NaCl) diffusion in foods during thermal processing using analytical and numerical solutions and at investigating the changes in NaCl concentrations during storage after processing. Potato, radish, and salmon samples in 1% or 3% NaCl solutions were heated at 90, 105, or 121 °C for 5 to 240 min to simulate pasteurization and sterilization. Selected samples were stored at 4 or 22 °C for up to 28 d. Radish had the largest equilibrium NaCl concentrations and equilibrium distribution coefficients, but smallest effective diffusion coefficients, indicating that a greater amount of NaCl diffused into the radish at a slower rate. Effective diffusion coefficients determined using the analytical solution ranged from 0.2 × 10^–8 to 2.6 × 10^?8 m²/s. Numerical and analytical solutions showed good agreement with experimental data, with average coefficients of determination for samples in 1% NaCl at 121 °C of 0.98 and 0.95, respectively. During storage, food samples equilibrated to a similar NaCl concentration regardless of the thermal processing severity. The results suggest that sensory evaluation of multiphase (solid and liquid) products should occur at least 14 d after processing to allow enough time for the salt to equilibrate within the product.     

Temperature Prediction during Thermal Processing of Surimi Seafood

ABSTRACT: An interactive temperature prediction for surimi seafood was constructed and validated. The prediction model showed good agreement with experimental temperature profiles. The heat transfer coefficient (h) decreased with an increase of temperature difference (δT) between the sample surface and the water bath. The h had an effect on the convective heat transfer, resulting in a slower overall heat transfer at the beginning of heating. Thermal diffusivity (α) of surimi seafood was determined from experimental temperature profiles. The α increased slightly as the temperature difference (δT) between sample and water bath increased. The low a observed at small δT reduced conduction, resulting in a slower overall heat transfer.     

Linear Model for Predicting Transient Temperature during Sterilization of a Food Product

The thermal behavior of a conductive canned food during retorting was represented using an input-output linear system, with a finite order N, and a time-delay. The input of the system was the retort temperature, the output was the temperature at the thermal center of the can. This model was applied for a typical sterilization process composed of two isothermal steps. The can internal temperature was expressed as a sum of N exponential terms in which appeared the constant holding retort temperatures, the come-up and come-down times and N pairs of heat penetration parameters identified in a preliminary experiment. The model was tested on a potato mash packed in metal cans processed in a vertical still retort. Temperatures estimated by the model agreed closely with those measured during thermal processing.     

Compression Heating of Selected Fatty Food Materials during High-pressure Processing

ABSTRACT: Compression heating of selected fatty and model food materials during high‐pressure processing was studied using a specially designed experimental system. Commercially available soybean oil, olive oil, beef fat, chicken fat, and salmon fish were studied at different pressures (150 to 600 MPa) and at different initial temperatures (25 to 70 °C). At an initial temperature of 25 °C, fats and oils showed higher compression heating values (up to 8.7 °C per 100 MPa) compared to 2 to 3 °C per 100 MPa for water. Though the compression heating of water depends on its initial temperature, oils have little or no effect of initial temperature.     

辅食营养补充品货架期内营养素的稳定性及叠加风险研究

本文主要对5种辅食营养补充品(1种辅食营养素撒剂和4种辅食营养补充食品)在货架期内营养素的稳定性及叠加风险进行了分析。稳定性试验结果表明,对于辅食营养素撒剂,维生素B₁的平均衰减率最高,为34.62%,其次是维生素D (30.77%)、B₁₂(30.14%)、B₆(29.41%)和A (29.10%),相对稳定的是钙(5.22%)。对于4种辅食营养补充食品,相对稳定的营养素均为蛋白质(0~0.93%)和钙(2.17%~11.30%),相对不稳定的营养素有维生素A (25.77%~30.74%)、D (22.37%~33.82%)、B₁(17.81%~25.93%)、B₂(25.00%~28.00%)、B₆(26.03%~33.33%)和B₁₂(13.11%~21.54%)。不同的品种其营养素的平均衰减率有一定的差异性。营养素叠加风险研究结果表明,婴幼儿在食用婴幼儿配方奶粉的同时摄入辅食营养补充品,需要根据食用的婴配粉营养素含量,科学选取适合的辅食营养补充品,以免产生某些营养素摄入过量风险。对于未食用婴幼儿配方奶粉的目标人群,同时选择婴幼儿米粉及辅食营养补充品食用则无摄入过量风险,反而对目标人群是一个很好的营养补充。     

Monitoring Food Product Temperatures during Convective Heating: Implications for Research Procedures

Turkey rolls were heat processed (105°, 135°, and 165°C) in an electric convection oven with loads of 2, 4, and 6 rolls. Data were analyzed when 50, 66, 83, and 100% of thermocouples (three/roll) reached 77°C. Processing time for 2 rolls, (min/load) and (min/kg), was significantly greater (p<0.05) only at 105°C, when 100% versus 50% of thermocouples were monitored. Energy consumed was not different for 2 or 4 rolls. Processing time differed (min/load) but not min/kg, when 4 and 6 rolls were heat processed at 135°C, depending on the percentage monitored. The percentage monitored significantly changed WH/load but not WH/kg, only when a load of 6 rolls was processed. Determining temperatures on the basis of readings from 50 to 100% of thermocouples did not affect energy data.     

Thermal Processing Canned Meat with Sub-Freezing Initial Temperatures: Thermal and Microbial Validation

Retorting from the frozen state is attractive with respect to product quality and economy and was investigated in canned bentonite and flaked ham. A two dimensional finite difference model was written in which thermal diffusivity varied with temperature. Heat penetrations were completed with initial temperatures of 0, -5°, -10°, -15° and -20°C. In ham, decreasing initial temperatures resulted in increased lag factors (j_h) but did not affect heating rate index (f_h). In bentonite, f_h but not j_h increased. D and Z of Clostridium sporogenes PA 3679 spores were not affected by previous freezing. Sub-freezing initial temperatures were judged to be consistent with safe processes if validated with heat penetration studies.     

南极磷虾虾糜热加工过程中的风味变化

为研究南极磷虾虾糜在热加工过程中的风味变化,采用蒸煮、烘炒热加工方式对南极磷虾虾糜进行处理,通过电子鼻和顶空固相微萃取-气相色谱-质谱联用技术,研究未经热处理的生南极磷虾虾糜和经热加工处理后的南极磷虾虾糜及其蒸煮液的挥发性风味物质。结果表明:热加工处理后,南极磷虾虾糜的风味发生了明显变化。其中,青草味、肥皂味、脂肪味、刺激性风味骤减,烘炒处理还产生烘烤香味和肉香味风味物质。生南极磷虾虾糜、蒸煮南极磷虾虾糜、南极磷虾虾糜蒸煮液和烘炒南极磷虾虾糜的样品中分别检测出32、29、34和55种挥发性物质。研究表明,热加工处理后,南极磷虾中总的挥发性成分呈现明显增多趋势,肥皂味、脂肪味、苦味、刺激性气味去除,烘烤香味、肉香味及腥味增加。     

True Thermal Conductivity Determination of Moist Porous Food Materials at Elevated Temperatures

Thermal conductivity (k) of bread samples, moisture content 5% to 44%, (w/w, wet basis) and porosity 0.18 to 0.90, was measured in a sealed stainless steel vessel using the probe method from 25 to 85°C. Significant differences were observed in measured thermal conductivity before and after air pressure was applied to the sample indicating the influence of vapor phase moisture migration on thermal conductivity. The difference increased as temperature and moisture content were increased. True thermal conductivity of bread was found to agree with predictions using a volume fraction model when moisture migration was completely suppressed at an applied air pressure of 18 atm.     

果蔬色泽在热加工和非热加工技术中的变化研究进展

色泽是果蔬十分重要的表观属性,与果蔬本身含有的天然色素高度相关,是判断其品质是否发生变化的重要指标之一。热加工以及非热加工技术广泛应用于果蔬产品的加工。传统果蔬加工技术以热力去皮、热烫、碱液去皮、干燥、油炸等热加工技术为主,加工中使用的高温易对果蔬的色泽品质造成不可逆转的影响。近年来,新型热加工和非热加工技术逐渐被探索,酶法去皮、红外线、超声波、脉冲电场、高压处理、低温等离子体等非热加工技术在果蔬加工维持色泽方面起到了积极的作用。然而目前综合两种加工技术对果蔬加工产品色泽影响的讨论和对比研究较少,明确各法的原理、使用条件、工艺参数及优缺点对于加工高质量的果蔬产品具有重要意义。因此该研究概述了各色素的结构特征以及理化特性,归纳和比较了热加工与非热加工技术的关键技术点和对果蔬色泽稳定性的影响,讨论了影响果蔬色泽的关键因素,最后对果蔬在加工过程中的应对的挑战提出了有关建议,以期为热加工与非热加工技术对果蔬的护色应用提供指导。     

食品加工厂的过敏原控制

本文介绍了过敏的机理及食品过敏原的种类,并就食品过敏原在食品工厂的管理与控制进行了探讨,指出过敏原的控制应从产品研发开始到消费者消费的全过程进行管理。     

食品非热杀菌研究中的科学问题分析

热力杀菌技术不仅能有效保障微生物引起的食品安全,而且非常经济,已广泛应用于食品工业,但其会导致食品品质劣变,包括颜色变化、口味改变、香气损失、营养破坏和质构变化。近年来,非热杀菌技术(nonthermalprocessing,NTP)引起了国内外政府部门、食品工业界和食品领域专家的关注,作为新兴食品杀菌技术,其能在较低温度下达到杀菌钝酶的效果,其中高静压技术已经成功商业化。本文通过对有关文献的分析以及结合自身的研究,对NTP 的有关研究进行了归纳总结,提出了NTP 研究中应该关注的杀菌、钝酶、品质、安全以及其他等5 个方面的问题,并进行了深入的分析和讨论。     

Thermal Processing Affects Properties of Commercial Shrimp and Scallops

Commercial shrimp and scallops were blanched, cooked and canned and their thermal conductivity, density and volumetric expansion were measured. Thermal conductivity was measured with a line-heat source technique while density and volumetric expansion were determined with a gravimetric method. Shrimp and scallops lost moisture and shrunk by <30 and 50%, respectively. Thermal conductivities decreased by <5%, whereas densities increased by 4%.     

肉类热加工过程中有害物质的形成与控制研究进展

肉类在煎炸、烧烤、蒸煮等加热过程中会产生令人愉悦的香气,但同时也伴随着多种有害物质的产生,如杂环胺、丙烯酰胺、反式脂肪酸、多环芳烃类等,这些物质会对人体健康造成极大危害.因此,探究肉类产品热加工过程中有害物质的成因及控制尤为重要.本文综述上述有害物质在肉类加热过程中的形成机理,总结上述有害物质现有的检测方法及控制手段,...     

Changes in Mushroom Texture and Cell Wall Composition Affected by Thermal Processing

ABSTRACT: The effects of thermal processing, calcium, and storage time on texture and cell wall composition of mushrooms were investigated. Whole fruit-bodies were blanched and retorted with addition of 0, 5, or 25 m M CaCl2. Firmness was determined as force for puncturing and toughness as shear force. Alcohol-insoluble fractions were extracted from fresh, blanched, and processed mushrooms. Proteins, carbohydrates, and chitin were analyzed in sequential extracts of alcohol-insoluble solids. Blanching caused an increase in force for puncturing but reduced force for shear. Further retorting did not affect texture, but toughness increased during storage. Calcium increased values for both textural characteristics possibly due to formation of cross-links between proteins and polysaccha-rides.