Ultrasonic cutting of foods: Effects of excitation magnitude and cutting velocity on the reduction of cutting work

The effects of vertical cutting velocity and the magnitude of ultrasonic excitation on the reduction of the work necessary to separate various food materials were investigated. Generally, cutting work increased with increasing cutting velocity but, at each particular cutting velocity, decreased with increasing magnitude of the ultrasonic excitation of the cutting tool. Interactions between cutting velocity and the maximum vibration speed at the cutting edge, which is determined by both excitation amplitude and excitation frequency, are significant. Depending on the food under action, the relative amount of cutting work reduction is either affected by the maximum vibration speed or, additionally, by vertical cutting velocity. No distinct effects of the excitation frequency (20 or 40 kHz) were observed.

Industrial relevance

Ultrasonic cutting is used in the food industry, especially for the separation of products consisting of layers with different rheological properties to achieve minimally damaged cut surfaces. The results of the study may be useful for selecting operational variables (cutting velocity, excitation amplitude) during cutting to achieve a controlled reduction of the cutting work.     

Ultrasonic cutting of foods with inclined moving blades

Cutting with devices excited by ultrasound is a promising alternative to conventional cutting when the materials contain particles which differ in stiffness and elasticity from the surrounding bulk or when they consist of layers which exhibit largely differing mechanical properties. Aim of the present study was to evaluate the impact of ultrasonic excitation and blade inclination (slice-to-push ratio) on cutting forces and cutting work of different foods with a fast-moving device which was excited in a way that the direction of vibration was parallel to the edge of the blade. The results show that ultrasonic excitation significantly reduces cutting force, that the magnitude of cutting force reduction largely depends on the product, and that cutting force and cutting work increase with increasing cutting velocity. Whereas these interactions are because of the micro-saw movement of the cutting tool, it was not possible to explain the product-dependent response to blade inclination.     

CUTTING RESISTANCE OF A RESTRUCTURED FRUIT BAR AS INFLUENCED BY WATER ACTIVITY

The cutting resistance, of thin rectangular strips of a restructured dehydrated fruit bar was measured over a range of water activity, 0.30-0.97. There was a 100-fold increase in cutting force as the product was dried from an initial cutting resistance of 4.4 N at a_w, = 0.86 to a maximum of 452 N at a_w= 0.33. Below a water activity of 0.33, samples became brittle and showed lower cutting resistances; for example, 68 N at a_w= 0.30. The major ingredients in the fruit product affecting cutting resistance were the level of apple puree and maltodextrin.     

TEXTURE AND STRUCTURE OF CRISPY-PUFFED FOOD PRODUCTS PART II: MECHANICAL PROPERTIES IN PUNCTURE

A puncture test was used to describe the mechanical and textural behavior of crispy-puffed food extrudates. Four criteria were identified from the force-time curves: (1) the average puncturing force, F_m, (2) the spatial frequency of structural ruptures, N_wr, (3) the average specific force of structural ruptures, f_wr, and (4) the crispness work, W_c. The discriminating power of these criteria was shown through the effects of moisture content and recipe composition in the extrusion-cooking process. Relationships between puncture criteria were also studied. The effect of water activity showed that the force related criteria described well the mechanical behavior of expanded extrudates.     

Mold-free Shelf-life Extension of Bakery Products by Active Packaging

ABSTRACT: Total elimination of oxygen (O₂) in modified atmosphere packaging of bakery products is difficult to achieve. Because of the typical porous texture of the packaging, air can be retained inside. The effect of O₂ absorbers alone or in combination with modified atmosphere on Eurotium amstelodami, E. herbariorum, E. repens , and E. rubrum growth was investigated. Cakes of 0.80 to 0.90 water activity ( a_w ) were packaged with different atmospheres (air, 100% N2; 70% N2:30% CO₂) and O₂ absorbers of 2 different absorption capacities. The use of absorbers with a suitable absorption capacity led to a significant increase of cakes with mold-free shelf life, regardless of a_w and pH level, at 25 °C.     

Ultrasonic cutting of cheese: Composition affects cutting work reduction and energy demand

Eight cheese varieties with different moisture (357–488 g kg^?1), fat (183–335 g kg^?1) and protein content (202–292 g kg^?1) were subjected to ultrasonic cutting using a 40 kHz guillotine sonotrode. Cutting force curves were evaluated with respect to ultrasound-induced cutting work reduction and energy demand of the sonotrode. With cutting velocity and ultrasonic amplitude set to 2500 mm min^?1 and 12 μm, respectively, composition had a significant effect on the response of the cheeses. Whereas cutting work reduction was mainly determined by fat-in-dry matter, the energy demanded by the sonotrode to maintain vibration was inversely interrelated to the ratio of moisture to solids-non-fat. Three selected cheeses were subjected to cutting experiments with systematically varied cutting velocity and amplitude. The results indicate that the cheeses respond differently to the cutting parameters, and that their careful adjustment is helpful for a target-orientated design of the process.     

Decontamination Efficacy of Combined Chlorine Dioxide with Ultrasonication on Apples and Lettuce

ABSTRACT:  The bacterial reduction of Salmonella and Escherichia coli O157:H7-inoculated apples and lettuce by ClO₂ at 0, 5, 10, 20, and 40 ppm with and without 170-kHz ultrasonic treatments for 3, 6, and 10 min, respectively, have been studied. The treatments of ClO₂ at 20 and 40 ppm for 3, 6, and 10 min or at 5 and 10 ppm for 6 and 10 min with 170-kHz ultrasonication caused 3.115 to 4.253 log reductions in Salmonella and 2.235 to 3.865 log reduction in E. coli O157:H7 on inoculated apples. Using combined ClO₂ and ultrasonication to treat 4.48 × 10⁴ CFU/g Salmonella and 1.07 × 10⁵ CFU/g E. coli O157:H7-inoculated lettuce, the bacterial reductions were 2.257 to 2.972 and 1.357 to 2.264 log, respectively. The residual ClO₂ decreased with increasing treatment times, over 80% of ClO₂ was detected after the 3-min treatment, and more than 70% remained after the 10-min treatment time. No bacteria were recovered from the posttreatment solutions of ClO₂ or ClO₂ combined with ultrasonication. The temperature of the ClO₂ treatment was 20.1 °C, and it increased to 40.1, 44.9, and 50.3 °C, with 170-kHz ultrasonic treatments for 3, 6, and 10 min, respectively, on apples.     

Influence of Oxygen, Carbon Dioxide, and Degree of Cutting on the Respiration Rate of Rutabaga

ABSTRACT: Both the O₂-consumption and CO₂-production rates of uncut and cut rutabaga were measured in a closed system. Compared to enzymatic and 1st-order linear models, a 2nd-order expression was found to best predict respiration rates under the conditions typically found in modified atmosphere packages. The concept of degree of cutting was introduced to quantitatively analyze the effect of wounding on respiration rates. A linear relationship was observed between the respiration rates at a fixed pO₂ and pCO₂ and the quantified degree of cutting injury. Mathematical expressions were developed that accurately describe the relationship between respiration rates, O₂ and CO₂ partial pressures, and the degree of cutting.     

蛋糕分切插纸一体机的设计与研究

针对蛋糕分切过程中出现的蛋糕局部坍塌、破损和残渣粘刀等问题,设计了一款以超声波切割刀为核心装置的蛋糕分切插纸一体机。该机包括超声波切割装置、蛋糕插纸装置和控制系统等关键机构,通过控制系统设置超声波切割刀振动频率、蛋糕旋转台转盘速度和蛋糕分切等分数等参数,进而实现不同类型、不同需求蛋糕的分切插纸,一次性完成蛋糕分切和插纸两道工序,并解决了蛋糕坍塌、破损和粘刀等问题。     

VARIATIONS IN FLEXURAL AND COMPRESSIVE FRACTURE BEHAVIOR OF A BRITTLE CELLULAR FOOD (DRIED BREAD) IN RESPONSE TO MOISTURE SORPTION

Mechanical properties of dried bread (a cellular baked product) equilibrated at different water activities (A_w) were measured using three-point bending and uniaxial compression to compare their responses to moisture sorption. The glass-to-rubber transition was clearly demarcated in all the mechanical property-A_w curves, although there were differences in critical A_w (0.32–0.56) at which the dramatic changes in mechanical properties occurred. The role of water appeared to be strictly that of a plasticizer where flexural mechanical parameters were concerned, leading to reduced modulus and fracture stress but increased fracture strain with increasing A_w. Uniaxial compression tests revealed moisture-induced mechanical antiplasticization effects on the material in the glassy state which resulted in maximum compressive fracture stress but minimum fracture strain over the A_w range from 0–0.56. Compressive modulus apparently was not affected much by moisture sorption up to an A_w of 0.43, above which it decreased sharply.     

Optimizing Processing Conditions for Milk Coagulation Using the Hot Wire Method and Response Surface Methodology

ABSTRACT: :
To evaluate the relationship between the factors affecting coagulation, the hot wire method was used for direct measurements of the renneting milk process as well as a central composite design with 3 factors: rennet concentration (x₁), renneting pH (x₂), and temperature (x₃). Second-order models for maximum voltage (Y₁), time at maximum voltage (Y₂), and coagulation time (Y₃) were employed to generate response surface contours. Optimum conditions for cutting time were found with x₁= 0.0278 R.U./mL milk, x₂= 6.60, and x₃= 35 °C, for which the responses were Y₁= 2854 ± 171 μV, Y₂, = 14.08 ± 3.04 min, and Y₃= 7.16 ± 1.12 min. No significant differences (p > 0.01) were found between the 3 responses obtained in the experiment and the ones predicted by the models. The use of the objective and non-destructive monitoring of curd formation and the response surface methodology can be recommended to optimize milk coagulation.     

A laboratory evaluation of a novel hot water cabinet for the decontamination of sides of beef

A hot water cabinet based on an idealized distributor design for the decontamination of sides of beef is described and a laboratory evaluation of this novel cabinet is reported.
Beef sides were inoculated with E. coli and exposed to mean water temperatures at the surface tissue ( T _f) of 83.5, 74.2, 66.0 and 44.5°C for 10 or 20 s. Mean log₁₀ reductions of bacteria for 10-s exposures were 2.23, 1.40, 0.91 and 0.2. For 20 s, reductions were 2.98, 2.14, 1.17 and 0.1. There was a significant ( P < 0.05) linear relationship between log reductions and T _f which varied with exposure time. At a T _f of 83.5°C with exposure times greater than 20 s, carcass bloom was judged to be permanently and adversely affected. At shorter times or with lower temperatures this did not occur.
Evaporative heat losses were well correlated with the pressure driving force ( r = 0.89) and gravity driving force ( r = 0.92) for air interchange between the cabinet and its surrounds.
The running cost using the distributor cabinet was one-third of that of an existing spray cabinet when compared at the maximum reduction of log 1.3 (95%) achieved by the spray cabinet. An additional advantage of the distributor cabinet is its constructional simplicity.     

A NOTE ON THE SENSITIVITY OF FINGERS, TONGUE AND JAWS AS MECHANICAL TESTING INSTRUMENTS

Deformation of a specimen between the fingers or in the mouth usually results in a significant deformation of the contacting tissues. This implies that the mechanical response is related to both deformations or, in other words, to the mechanical resistance of the combined systems. Since the latter form an in-series configuration, the combined mechanical resistance (M_c) is given by:
where M₁ and M_x are the resistance of the sensory testing system and the test specimen, respectively. Thus, M_c can be a function of the geometry and the rate of force application. The equation provides a simple explanation as to why there are differences in the sensing range between the fingers and the jaws and why the human senses are practically insensitive to hardness beyond certain levels. The model indicates that the sensitivity decreases rather rapidly after the ratio M_x/M₁ becomes greater than about 0.05, but leaves unanswered the question whether, or to what extent, we can compensate for the loss of sensitivity by additional information or modification of the testing procedure.     

基于电子视觉系统的软胶囊自动分选机的开发研究

针对国内食品、医药行业软胶囊制品生产过程中的胶囊分选问题,摒弃原有的人工分选模式,采用电磁振动上料器自动上料、链条输送机构无级调速匹配输送、计算机视觉系统间接判别软胶囊质量、高速喷嘴吹去超差软胶囊制品的方法,来分选软胶囊制品,最高分选速度可达10粒/s以上。该技术最大的优点在于一是极大地提高了分选效率,二是避免了由于人工分选靠感觉和经验来判别软胶囊制品的大小,而把合格制品误判为不合格,或者把不合格品判为合格品,造成误检的情况。     

基于模糊PID控制的电磁式定量给料系统

为解决传统电磁式定量给料系统开环控制过程中给料速度设定随意性较大,无法根据智能控制策略动态调节给料速度的问题,提出并设计了一种基于模糊PID控制的电磁振动定量给料系统;设计了系统整体机械结构,通过理论分析得到了可控硅导通角与振幅的数学关系;并在此基础上建立了简化的电磁振动给料机二阶数学模型。仿真试验结果表明,该系统动态跟随性较好、控制精度较高、响应速度较快和鲁棒性较高,具有较好的应用前景。     

花样激光自动裁剪系统的DSP控制

为了实现服装面料优质高效裁剪,引入激光裁剪技术,采用具有丰富外设资源的DSP处理器TMS320F2812,运用正切运动插补算法,研究开发了激光自动裁剪控制系统,克服了传统机械裁剪刀具切削引起的震动,不但提高了面料或花样裁剪的质量,而且也提高了裁剪效能。在激光裁剪的原理和自动裁剪系统的总体设计基础上,完成了结构设计和硬件设计,同时配合软件设计,应用SD卡存储及FAT32文件管理程序实现轨迹控制文件的传输,结果表明：激光自动裁剪具有高精度高效率的裁剪效果。     

MODELING FREQUENCY DISTRIBUTION of STEADY-STATE O2 PARTIAL PRESSURES IN MODIFIED-ATMOSPHERE PACKAGES

A mathematical model was developed to predict the frequency distribution of steady-state O₂ partial pressures in modified-atmosphere packages of fresh and minimally processed fruits and vegetables. Variation in O₂ uptake was predicted to have relatively larger influence on the package O₂ distribution than variation in film permeability to O₂. the model also predicted that the range of O₂ partial pressures in the packages would be larger for the products with lower K_1/2 (a constant in product O₂ uptake equation) values. the percent deviation of package O₂ partial pressures from [O₂]_med increased with [O₂]_med up to about 3 kPa and gradually decreased thereafter. Package O₂ distribution was symmetrical at higher [O₂]_med but became gradually asymmetrical with decreasing [O₂]_med from 6 kPa. the model was used to predict target [O₂]_med for the design of modified-atmosphere packages for different probability levels of having package O₂ being equal to or less than a minimum tolerable level of the product.     

INFLUENCE OF UNIAXIAL COMPRESSION RATE ON RHEOLOGICAL PARAMETERS AND SENSORY TEXTURE PREDICTION OF COOKED POTATOES

The effect of uniaxial compression rate (20–1000 mm/min) on the parameters: Stress (σ_ftrue), strain (ε_fHencky) and work to fracture (W_f), modulus of deformability (E_d), maximum slope before fracture (E_max) and work during 75% compression (W_total) was investigated for ten potato varieties. Multivariate data analysis was used to study the correlation between and within the sensory and nonsensory measurements by Principal Component Analysis (PCA) which showed σ_ftrue, E_max, W_f, and W_total to explain the same type of information in the data, and ε_fHencky versus E_d another type of information in the data. The deformation rate had a large effect on ε_fHencky. Nine sensory texture attributes covering the mechanical, geometrical and moistness attributes were evaluated. Relationships between uniaxial compression data at various deformation rates and the sensory texture attributes were studied by Partial Least Squares Regression (PLSR). A minor effect of deformation rate on the correlation with the sensory texture properties was obtained. Mechanical properties were predicted to a higher extent than the geometrical attributes and moistness. The prediction of the mechanical, geometrical and moistness attributes increased largely by using uniaxial compression supplemented by chemical measures such as dry matter and pectin methylesterase, but here no relevant effect of deformation rate was obtained.     

超声波缝合涤纶织物缝口的力学性能

通过定速拉伸超声波缝合涤纶织物缝口,比较不同因素组合下的缝口力学性能,揭示超声波花轮压力、花轮速度、功率与织物缝口力学性能的关系。研究表明：超声波花轮压力越大,花轮输送速度越小,超声波功率越大,织物缝口的力学性能越好。缝口断裂强度、断裂伸长率、断裂功与提出的超声波缝合影响因子（压力×功率/速度）呈极显著的正线性相关,该影响因子可以用来表征超声波缝合织物缝口的力学性能,运用该影响因子可简化超声波缝纫机的调节操作过程。     

干切混凝土时金刚石锯片振动及噪声的研究

干切混凝土时,金刚石锯片在实际工作过程中产生的振动和噪声是非常严重的。文章从理论上分析了混凝土锯切过程中的强振动、高噪音的原因。通过改变锯切速度、进给速度、切深以及通过采用两种不同的基体结构的锯片,研究了不同的切削参数以及锯片的结构对锯片振动和噪声的影响。在不同的锯切工艺参数和锯片结构下,测量了噪声值、噪声功率、噪声电压、振动功率和振动幅值,并对其进行频谱分析。可以从锯片的基体结构、金刚石节块的结构、锯切工艺以及锯机的整体性能等方面来进行改进,从而达到降低噪声与振动的目的。本文在理论分析和实验的基础上提出了一些降低噪声和振动的方法。