Understanding potato chips crispy texture by simultaneous fracture and acoustic measurements, and sensory analysis

The fracture and acoustic properties of six commercial potato chips that differ in sensory hardness and sensory crispness were analysed and related in this work. Principal component analysis showed a correlation among the sensory attributes and the instrumental parameters (both mechanical and acoustic). Two components mainly explained the behaviour of the different potato chips. The first component was positively related to the number of force and sound events, to sound pressure level maximum, to the area under the force curve, and to sensory crispness, and negatively related to fat content; and the second component was positively related to the gradient (slope of the first part of the curve), the potato chip thickness, and to sensory hardness and sensory crispness. The behaviour of the different potato chips was explained by either one of the two components or by both components. Results indicate that certain degree of sensory hardness is necessary for higher crispness perception.     

Methodological developments in crispness assessment: Effects of cooking method on the crispness of crusted foods

A new method was developed to assess the texture of crispy-crusted foods with a soft, high-moisture core. This method, applied to commercial pre-cooked chicken nuggets, combines characteristics derived from the force/displacement curves of the whole sample with characteristics of the simultaneously emitted sound. The use of a not-sharp blade probe to perform the test proved to be an effective technique for characterizing the texture of chicken nuggets after different final cooking processes. The force curves of the samples differed with the cooking process. Deep-fried samples and those cooked in a conventional oven presented jagged force curves and acoustic signals with many peaks, both characteristics of crispy products. The curve profiles of microwaved samples were drastically different and typical of tough, gummy products. The use of a susceptor package in microwave heating improved the crispness of the samples. The number of sound peaks was the acoustic parameter that best discriminated between the samples. It was found that although the moisture and fat contents of the core and crust are closely related to the texture characteristics, samples with similar water contents can have very dissimilar crispness characteristics. The fat content of the core did not change significantly with the final cooking process in any of the samples.     

ACOUSTIC ENVELOPE DETECTOR FOR CRISPNESS ASSESSMENT OF BISCUITS

The crispness of food materials based on the force/displacement behavior and their acoustic nature was assessed using an Acoustic Envelope Detector (AED) attached to the Texture Analyzer, wherein six kinds of biscuits were used: Carr's Table Water, Crackerbread, Digestive, Dutch Crispbakes, Rich Tea fingers and Shortbread. The force/displacement and acoustic signals were simultaneously recorded during the breakup of biscuits. For each detected acoustic signal, there was a sudden drop in the compression force. The analysis of the force/displacement curve demonstrated the links between the second derivative of force curve and the acoustic event, indicating the energy released through the air of these crack events. The acoustic behavior of the biscuits was assessed in terms of maximum sound pressure level and the number of acoustic events, which were further interpreted as the acoustic events per unit area of newly created surface area and the acoustic event per unit time. The acoustic ranking of biscuits from instrumental assessment was in very good agreement with that from sensory panel tests. The normal integration time (1.25 ms) for the AED was generally effective in detecting acoustic signals for crisp biscuits, but a shorter integration time (0.25 ms) was found advantageous in detecting acoustic signals that occur within a very short time period and gave better differentiation of crisp biscuits.     

Characterization of crispness of French fries by fracture and acoustic measurements,effect of pre-frying and final frying times

The influence of pre-frying and final frying time on the crispness of French fries was evaluated by simultaneous analysis of the fracture and acoustic properties during instrumental simulation of human chewing. The analysis of the frequency distribution of the force and sound events corresponding to the crust of the French fry reflected an effect of both pre-frying and final frying time on instrumental crispness. Up to 60 s pre-frying, an increase in the number and magnitude of force and sound events was found, which reflect an increase in crispness. The increase in final frying time increased crispness, but it cannot counterbalance a lack of pre-frying. The moisture content of the whole French fries cannot explained the effect of pre-frying on crispness. Conversely, the effect of pre-frying can be explained when considering only the moisture content of the crust. Pre-frying may allow an easier loss of water from the crust during final frying, which will enhance its crispness.     

ACOUSTIC TESTING OF SNACK FOOD CRISPNESS USING NEURAL NETWORKS

The crispness of selected snack foods, Pringles potato chips, Paprika extruded snack and Munchy crackers, was evaluated by crushing the snack samples with a pair of pincers, and analyzing the frequency domain spectra of acoustic patterns by the neural networks (NNs). The inputs for training the NNs comprised 102 amplitudes of sound signals in 0–7 kHz frequency range at the intervals of about 69 Hz with moisture content or crispness grades as outputs. Both backpropagation (BPNN) and probabilistic (PNN) models showed good performance in classifying the snack foods into four grades of sensory crispness. The prediction accuracy of PNN models ranged approximately from 96 to 98% and was higher than the accuracy of BPNN models by about 10 to 25%. Results showed that frequency domain spectra of acoustic signals could be successfully analyzed by the NNs for predicting the crispness of snack food products.     

THE INFLUENCE OF COOKING METHOD ON THE QUALITY OF PORK PATTIES

Pork patties were subjected to traditional frying, cooking in a microwave oven (microwaves  +  grill), hot air cooking in a cyclojet (Electrim JI-9101 RP, Taiwan) and cooking in a steam-convection (combi) oven (hot air  +  30% steam) (BECK FCV 4 EDS, BECK GmbH, Jagsthausen, Germany). Products cooked in the combi oven (BECK FCV 4 EDS) were characterized by the smallest cooking loss, the highest retention of water and the lowest content of fat compared to other samples. The content of hydroxymethylfurfural in fried and cyclojet-cooked patties was almost twofold higher than in microwave and combi oven-cooked samples. The intensity of lipid oxidation was also higher in fried and cyclojet-cooked meat than in the other two products. The intensity of meat flavor was the strongest in the combi oven-cooked patties. All products were characterized by a low intensity of fatty flavor. The highest scores for overall acceptability were given to the combi oven-cooked patties, whereas the lowest scores were given by the panelists to the microwave-cooked patties.

PRACTICAL APPLICATIONS

Pork patties are an important meat product both in catering production for direct consumption and in convenience food industry when intended for refrigerated or frozen storage. As cooking is a main stage in preparation of patties for consumption, it is essential to use a method of cooking that ensures the high nutritional and sensory quality of products. Most often, pork patties are subjected to deep frying or traditional frying; however, several other cooking methods can be used. The present work shows that the combi oven cooking enables production of patties of desirable nutritional and sensory characteristics and low content of unfavorable compounds.     

Effect of Corn Flour, Salt, and Leavening on the Texture of Fried, Battered Squid Rings

ABSTRACT: The effect of the addition of corn flour and salt on the textural properties of a commercial dry-mix batter used as coating in fried, battered squid rings was studied. Although salt-containing formulations had significantly lower viscosity values than the other samples, the batter pickup values were not significantly different. The crispness of the fried, battered squid rings was measured. The peak force of penetration, slope of the curve, and area up to the peak force did not show big differences, except the values for the formulation that contained leavening agent. In this case, the force value was significantly lower than the rest and the penetrometry profile was also different, corresponding to a crispy product. Finally, the influence on crispness of time lapsed after frying was also studied.     

稻米油调和油煎炸应用研究

通过与棕榈油对比180℃下炸制薯片以及评估薯片感官喜好度、质构、口感及粘牙性等差异来评价稻米油调和油的煎炸应用性能。结果表明:采用稻米油调和油煎炸的薯片中多不饱和脂肪酸含量显著高于棕榈油(P<0.05),且其薯片的整体感官喜好度、质构口感、酥脆度、粘牙喜好度,均显著优于棕榈油薯片(P<0.05)。在加速氧化条件下,采用稻米油调和油炸制的薯片的酸价、过氧化值均与棕榈油炸制的薯片无显著性差异(P>0.05),且远低于GB 16565-2003的规定。在加速存储过程中,谷维素却得到了很好的保留。总之,稻米油调和油具有良好的煎炸性能。     

食品脆度的客观表征及其通用测量公式的研究

食品的脆度指标因构成因素复杂,虽有少量探索,目前为止尚没有形成比较一致的客观表征和测量方法。本研究以具有脆度属性要求的各种蔬菜水果类食品为对象,建立食品的感官脆度评价与仪器测定质构图中提取的各种参数的相关性。把所得的力、斜率、面积、面积/ 距离等参数与感官平均脆度值进行相关性分析,结果表明：斜率与感官脆度值具有最高的相关性,据此建立脆度指标的表征模型。以饼干类食品对该模型进行验证,表明该模型对蔬菜水果及饼干类食品有较好的应用前景。     

INSTRUMENTAL MEASURES OF BITE FORCES ASSOCIATED WITH CRISP PRODUCTS

The usefulness of a bite force apparatus for measuring bite forces generated while biting extruded crisp snacks was assessed. Snacks were produced using a twin‐screw extruder, and their textural properties were modified by equilibrating to water activities ranging from 0.11 to 0.44. Maximum force to bite, stress, duration and area under the bite force curve were analyzed and compared to perceived sensory crispness, hardness, brittleness and sound duration evaluated by eight individuals. Maximum bite force and stress were significantly related to hardness, brittleness and crispness showing for the first time, and the relationship between sensory crispness of extruded crisp products and hardness was measured intraorally.     

Relationship of carrot sensory crispness with acoustic signal characteristics

The purpose of this study was to investigate the relationships of carrot sensory crispness with acoustic signal characteristics and microstructure after storage under common shelf conditions. The results showed that carrot sensory crispness declined significantly after the 14th day of storage, and the sensory score reduction was nearly up to 42% after the 28th day of storage. The carrot sensory crispness was positively related to both the waveform index (r = 0.785, P < 0.01) and sound intensity (r = 0.732, P < 0.01) of the acoustic signals in the time domain. Hilbert–Huang transform is a useful method for the observation of frequency changes in the time domain. The overall frequency bands were distributed around 200–2000 Hz through the Hilbert spectra. Rupture did not occur until the 14th day (crispness declined significantly) of storage through the scanning electron microscopy images of microstructure, and the crispness declined gradually with the increase of rupture.     

RELATIONSHIPS BETWEEN SENSORY CRISPNESS AND OTHER SENSORY AND INSTRUMENTAL PARAMETERS1

Twenty subjects judged the crispness, loudness, and firmness of sixteen food samples by both biting and chewing and by only biting the foods. These subjects also scored the foods for thirteen textural qualities. Instrumental measures of slope, peak force, and deformation to fracture were obtained for the sixteen foods from a snap test at four deformation rates. Whether a subject judged an attribute by the bite or the bite and chew technique made little or no difference in the sensory judgments. Crispness appeared to be very closely related to loudness and less closely related to firmness. Loudness of the chewing sounds was more closely related to crispness than to firmness. Of the sensory qualities studied, loud, snap, and crackly were the three most closely related to crispness. Of the instrumental parameters Young's Modulus generally had the highest correlation with the crispness of all foods and peak force generally had the highest correlation with firmness. Deformation rate had minimal effects on measures of flexure or peak force, but its effects on Young's Modulus were frequently large and irregular. A vibrotactile-acoustical hypothesis for crispness is proposed.     

Estimation of crispness and consumer acceptance of fried potato chips by mechanical and acoustic measurements

Fried potato chips retaining various moisture contents (MCs) (2.21–9.20%) were analysed to estimate the intensity of crispness and consumer acceptance by texture and acoustic measurements. The MC of the chips was highly correlated with the mechanical maximum force (MMF) in the texture measurement, total area (MTA) and number of sound peaks (NSP) in the acoustic measurement. The intensities of crispness and consumer acceptance decreased as the MC of potato chips increased. For the predictive models established, the combined use of mechanical and acoustic parameters was shown to better predict sensory crispness intensity [R² = 0.975, root mean square error of prediction (RMSEP) = 0.138] and consumer overall liking (R² = 0.966, RMSEP = 0.111) than either parameter alone. Based on the instrumental‐sensory crispness equivalent table established, the estimated values of the MTA were below 71.24, while the NSP should be above 22.81 to meet ‘slightly like’ category of consumer acceptance.     

Influence of the frying temperature on acrylamide formation in French fries

It is well established that high oil temperatures during frying strongly increase acrylamide formation in French fries, but it is less clear, which temperature or rather which part of a temperature profile is relevant and if rules or regulatory measures should be established in respect of frying temperature, on which temperature they should refer. In most fryers, the oil temperature strongly drops on adding the potato sticks and may not fully recover up to the end of the frying process (depending on the amount of potato added in relation to the volume of oil and the heating power of the fryer). Since acrylamide is formed towards the end of frying, the temperature during the second half of the process is more important than that regulated by the thermostat. The profile of the frying temperature was optimized regarding product quality (crispness, flavor) and acrylamide formation. An initial temperature of 170–175 °C dropping to 140–145 °C and a virtually isothermal frying at 160 °C resulted in products of similar quality and acrylamide content. At initial temperatures below 160 °C and with main frying temperatures below 140 °C, crispness and the flavor of the French fries suffered: the sticks dried out and became oily. Isothermal frying at 167–170 °C resulted in approximately doubled acrylamide content compared to conditions that were optimal in respect of culinary quality and low acrylamide formation, showing that rules on the initial temperature alone are inadequate to ensure low acrylamide contents. Optimized fryers should program temperature: allowing an initial temperature drop, but then efficiently heating to prevent the temperature dropping below a given limit; after the end of frying, the initial temperature must be restored before frying the next portion.     

Feasibility of non-destructive evaluation for apple crispness based on portable acoustic signal

In this paper, apple crispness was evaluated by sensory evaluation and compared with non-destructive measurements of portable acoustic signal to discuss the feasibility of non-destructive evaluation for apple crispness based on portable acoustic signal. Acoustic eigenvalues from the acoustic signal were processed by time domain and Hilbert–Huang transform (HHT), followed by analysing the correlations with apple crispness that had been evaluated via sensory evaluation. Multiple linear regression (MLR) and artificial neural network (ANN) were applied to predict apple crispness. The results proved that crispness correlates significantly (P < 0.01) with four acoustic eigenvalues, including waveform index, sound intensity, energy of low frequency and energy of high frequency. The average relative error of apple crispness predicted by ANN was 1.42 ± 1.9%, remarkably lower (P < 0.01) that of MLR (6.79 ± 5.64%), implying that the model predicted by ANN is more accurate than that of MLR.     

自加热茄汁酥肉加工工艺的研究

采用猪后腿肉为原料,以水分含量、剪切力、质构和感官评分为考察指标,研究挂糊组分、初炸温度、初炸时间、复炸温度和复炸时间等因素对自加热茄汁酥肉品质的影响规律.在单因素试验的基础上,采用L9(34)正交试验对自加热茄汁酥肉的工艺进行优化.结果 表明,挂糊组分对剪切力、硬度、咀嚼性影响显著(P＜0.05),初炸温度对硬度、内...