Effects of the sound of the bite on apple perceived crispness and hardness

The effects of the manipulation of the sound produced while biting into apple samples, a non-dry food, was investigated. In Experiment 1, participants rated the perceived crispness of flesh cylinders obtained from three apple cultivars differing in their texture profile: ‘Renetta’ (white ‘Renetta Canada’), ‘Golden’ (‘Golden Delicious’), and ‘Fuji’. Participants might hear the veridical sounds they made when biting into an apple cylinder without any frequency adjustment (0 dB filter) or with high frequencies attenuated (either by −12 dB or by −24 dB). Perceived crispness was significantly lower when any of the reductions were applied than when no filter (0 dB) was used. In Experiment 2, new participants rated both crispness and hardness of ‘Renetta’ and ‘Fuji’ cylinders. The sound of the bite could be unfiltered (0 dB), reduced in its high frequencies (−24 dB), or globally reduced (the microphone was switched off). Crispness, again, was perceived as significantly lower with any of the sound reductions. Interestingly, perceived hardness was significantly affected by the sound information as well: Hardness was rated as being significantly lower when a global sound reduction was applied than when the sound was unfiltered. We demonstrated, for the first time, that sound information plays an important role even for the evaluation of hardness, a property believed to be primarily oral/mechanical.     

Effect of blending cassava starch,rice, waxy rice and wheat flour on physico-chemical properties of flour mixtures and mechanical and sound emission properties of cassava crackers

A simplex-centroid design was used to investigate the physico-chemical properties of flour mixtures composed of cassava starch, rice flour, waxy rice flour and wheat flour on the one hand and linear expansion, texture and sound emission properties of crackers, made from theses mixtures on the other hand.     

Modeling water sorption dynamics of cellular solid food systems using free volume theory

Water sorption and dynamical properties of bread crust were studied using gravimetric sorption experiments. Water uptake and loss were measured while relative humidity (RH) was step-wise in- or decreased. Experimental results were compared with Fickian diffusion models and empirical models like the exponential and power-law model. From comparison of experimental sorption curves and the power-law model for short times it followed for all bread crust that the diffusional coefficient n is close to one. It turned out that this is not due to so-called case II diffusion and water transport that is limited by relaxation of the solid material but due to the fact that RH did not instantaneously but gradually increased to the set value.Sorption curves of isotherm experiments could be best described by the Fickian diffusion model for low RH and by the exponential model for large RH. Transport rates depend on moisture content and show a maximum around RH = 0.7, corresponding to a water mass fraction ω₁ = 0.12. Diffusion rates could be well described by free volume theory up to the maximum, but this theory could not explain the strong decrease at higher ω₁. Indications for a local glass-rubber transition at room temperature were found near a water mass fraction ω₁ ≈ 0.09. This corresponds very well to the start of the crisp–non-crisp transition as measured by a sensory panel, but not to the glass-rubber transition at ω₁ ≈ 0.12 as measured by other techniques like Differential Scanning Calorimetry. So it seems that more than one glass-rubber like transitions may be important to describe the properties of heterogeneous cellular food systems.     

Optimisation of processing variables in the preparation of sweet potato chips using response surface methodology

Models capable of predicting the product quality of sweet potato chips have been developed using response surface methodology and used to determine the optimum processing conditions. Moisture loss, oil uptake, crispness (measured using a bending-snapping test in the TA.XT2 Texture Analyser), and sensory attributes such as colour, flavour, and texture were used to assess the product quality in the preparation of sweet potato chips. The optimum conditions which were attained for maximum moisture loss (11.65% on wet basis), minimum oil uptake (2.57%), crispness (794.37 g), colour score (7), flavour score (7) and texture score (7) were: frying temperature, 174.7 °C; salt concentration, 0.45%; citric acid concentration, 0.37%; potassium metabisulphite concentration, 0.65%; and frying time, 26 s.     

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.     

Correlating Perceived Crispness Intensity to Physical Changes in an Amorphous Snack Food

Abstract

A crispy amorphous food was equilibrated to different moisture contents. These samples were tested for the glass transition temperature (T_g) using mechanical methods. The brittle-ductile transition temperature (T_b) was determined using force-deformation methods. Finally, the temperature where the onset to the sharp decrease in crispness intensity occurred (T_ci) was determined by a 10-member sensory panel rating the crispness intensity. The relationships of the T_g, the T_b, and the T_ci were determined using three different statistical methods. The results of this research indicated that the T_g, the T_b, and the T_ci were related to one another as a function of moisture content.     

Performance of cellulose derivatives in deep-fried battered snacks: Oil barrier and crispy properties

The performance of batters containing cellulose derivatives (methyl cellulose (A4M), three hydroxypropylmethyl celluloses (E4M, F4M and K4M) with different degree of hydroxypropyl and/or methyl substitution and carboxymethyl cellulose (CMC)) to produce crispy deep-fried snacks crusts was studied by using a deep-fried crust model. Their performance was compared in terms of their ability to retain moisture content, to decrease oil content and the effect on crispness. Thermogelation properties of the cellulose derivatives depended on the type and degree of substitution. All increased the water content and decreased the oil content of the deep-fried crusts, except for CMC, which does not thermogelate and did not increase the amount of water retained in the crust, although a decrease in the oil content was found. The highest oil reduction and the lowest water retention were found for the cellulose with the lowest level of methyl substitution (K4M). The sound emitted during fracture of K4M crusts had higher intensity than the other cellulose derivatives indicating a crispier crust.     

Cross-linking of wheat starch improves the crispness of deep-fried battered food

Wheat starches with different degrees of cross-linking were used to study the effect of starch gelatinization in the batter and crust characteristics of deep-fried battered food. Pasting properties, viscosity and batter pick up as well as moisture and oil content and crispness of the fried crusts were evaluated. In batters prepared with a constant solids/water ratio, the cross-linked starches increased batter viscosity and consequently the batter pick up. Batters, with comparable viscosity were prepared by varying the solid/water ratio which gave the same batter pick up.The pasting properties of cross-linked starches showed that the higher the cross-linking the more resistant was the starch to gelatinization and granule disintegration. In batters with a constant solids/water ratio, batter with high cross-linked starch had more water loss during frying. Cross-linked starches had lower moisture content after storage and less oil was retained after frying. Crispness, measured instrumentally as sound intensity, was the highest for the high cross-linked starch at 1 and 20 min after frying.Batters prepared with the same viscosity were used to study the effect of cross-linked starches when the pick up was the same. To obtain comparable viscosities between the batters, the batter with native starch was prepared using the lowest mixing water content and the one with high cross-linked starch with the highest. The batter with the high cross-linked starch, although it had the highest addition of water, had the best crispness after frying.In conclusion, high cross-linking of wheat starch enhances crispness perception of deep-fried battered food.     

Impact of air humidity in industrial heating processes on selected quality attributes of bread rolls

The object of this research was to study the real time percent humidity of the air and consequently to analyze this humidity influences on bread rolls. An industrial baking process was visualised by the use of a high-temperature humidity sensor to measure the level of percent humidity of the air (V% H₂O) in relation to the different H₂O-steam amounts (SA). In this study H₂O-SA from 0 to 3.256 L(H₂O) m⁻³ of the oven volume were used. After steaming the results of gas moisture without product (GMWoP) showed a higher maximum (approx. 5%) of the percent humidity of the air than the gas moisture with product (GMWP). The trials reveal that the presence of products (bread rolls) is a factor in attaining an increase in the percent humidity of the air which influences product quality. Baking with adequate percent humidity of the air bread roll volume increased by 20% compared to trials without steam. New methods were used to quantify product parameters like crust thickness, compression-force and crispness and to find out correlations with the area under the GMWP curve (auc). Strongest correlations with auc GMWP were found for mean and maximum compression-force. Furthermore, it was shown that the increase in crust thickness, lightness and colour change is mutually dependent on an increase change in the total GMWP.