CRISPNESS AND CRUNCHINESS JUDGMENT OF APPLES BASED ON CONTACT ACOUSTIC EMISSION

Contact acoustic emission (AE) measurement, together with a puncture test, were used to evaluate the crispness and crunchiness of three apple cultivars. A storage program was used to induce changes in apple crispness and crunchiness. The instrumental measurements were compared with the results of sensory evaluation.
It was found that crispness and crunchiness could be evaluated instrumentally by measuring firmness, AE events, mean AE amplitude or the product of AE events and mean AE amplitude. For one cultivar, however, firmness was not correlated with any sensory attribute. Generally, the best correlation with sensory attributes was found for the exponential value of AE events. Contact AE allows the measurement of sensory crispness or crunchiness for a given apple cultivar or independently for any apple cultivar. Contact AE can be considered as a useful method for the evaluation of sound properties of wet-crisp foods.

PRACTICAL APPLICATIONS

Contact acoustic emission method can be used for instrumental evaluation of crispness and crunchiness of apples. The method allows more accurate evaluation of these attributes than firmness measurement. There is a chance to extend the application to other wet-crisp foods and to use the method together with other destructive tests, like texture profile analysis or single edge notched bend.     

New contact acoustic emission detector for texture evaluation of apples

A new contact acoustic emission detector (CAED) was developed for the instrumental texture evaluation of apples. The goal of this work was to determine the relations between instrumental parameters and sensory texture attributes, and to develop calibration models for prediction of the sensory texture of apples with CAED. Seven apple cultivars were used for the construction and validation of the models. CAED is particularly useful for evaluation of sensory crispness, crunchiness and hardness. There is also a significant correlation of acoustic emission counts with juiciness, mealiness and overall texture. Validation of the models indicates better prediction of these sensory attributes by total acoustic emission counts than prediction by puncture firmness in terms of variance explained, root-mean-square of a model prediction, and bias.     

五种苹果质构测定方法的比较及与感官评价的相关性分析

为比较5种苹果质构不同测定方法,采用剪切法、穿刺法和TPA压缩法测定了辽宁地区5种主栽苹果的质构特征,同时研究了不同测试条件对测定指标的影响,并分析了仪器测定与感官评价结果的相关性。结果表明剪切、穿刺和TPA压缩均能测得苹果的硬度特征,并区分不同品种间的差异,去皮果肉硬度大小依次为王林 > 红富士 > 国光 > 乔纳金 > 黄元帅;穿刺法检测显示果皮对苹果质构有显著影响(P<0.05),且不同穿刺部位的质构差异显著(P<0.05),其中果顶部位穿刺硬度值最大,其次为果肩和赤道;与感官评价相关性分析显示最大穿刺模量与感官脆性极显著相关(r=0.638,P<0.01),可作为苹果脆性的表征指标;对TPA法,随着压缩形变量增加,苹果硬度测定值显著增加(P<0.05),而内聚性显著减小(P<0.05),且形变量为25%时与感官评价相关性最好。本研究表明穿刺法和TPA法均适用于苹果质构的测定,果皮及穿刺位点对穿刺影响显著,最大穿刺模量可用于表征苹果脆性指标;压缩形变量为25%时TPA法所测得质构参数与感官评价结果相关性最好。     

EFFECT OF MANNITOL TREATMENT ON ULTRASOUND EMISSION DURING TEXTURE PROFILE ANALYSIS OF POTATO AND APPLE TISSUE

An ultrasound acoustic emission (AE) signal was recorded during texture profile analysis (TPA) of potato and apple tissue with different texture. The acoustic sensor was in contact with the sample through solid medium. Texture of the tissue was controlled by soaking it in different mannitol solutions. Both TPA and AE parameters change with the texture of potato and apple samples. However, correlation coefficients of linear regression of acoustic parameters are higher than TPA parameters and all of them are significant at a higher confidence level. Critical stress and strain indicate micro‐cracking of the material and they increase with decreasing tissue turgor. The ratio of the critical stress to hardness allows an analysis of sound duration. The sound lasts longer when the tissue is more turgid as a result of the decrease of critical stress to hardness ratio. Counts of AE recorded in the whole TPA test decreased logarithmically with tissue osmolality. The article showed that contact AE can be used for texture evaluation of potato and apple tissue.     

Texture of Vacuum Microwave Dehydrated Apple Chips as Affected by Calcium Pretreatment, Vacuum Level, and Apple Variety

ABSTRACT: The effects of calcium pretreatment, vacuum level, and apple variety on the texture of apple chips, processed using a combination of air drying and vacuum microwave dehydration (VMD), were determined. Pretreatment of apple slices by immersion in 1-5% aqueous CaCl₂ significantly increased crispness of chips as determined by instrumental and sensory analysis; however above 1%, chips were perceived as bitter. Higher vacuum applied during VMD significantly lowered density and increased crispness of chips. This effect was mediated by the vaporization of water in the interior of the chip, which caused expansion of the tissue. Chips made from Fuji apples had higher calcium contents, and were crisper than Red and Golden Delicious apple chips. Microstructure of the chips evaluated by scanning electron microscopy indicated that chips with thicker cell walls and large internal voids were crisper.     

江苏富士苹果的理化及感官特性分析

江苏省苹果以丰县为集中产地,富士为主栽品种,隶属于黄河故道产区,为明确其鲜食特性的地域特点,对丰县富士糖酸含量、色泽和质构等理化指标和硬性、易碎性、多汁性、酸甜度等感官属性进行了测定,并与陕西富士进行了比较。结果显示丰县苹果蔗糖和苹果酸含量偏低,分别为陕西苹果的75.88%和58.90%。江苏苹果果皮L*为64.37,a*值为11.19,b*值为32.12,a*值低而L*、b*值高于陕西苹果,说明果皮红色弱而偏黄色;果肉L*值为81.19,b*值为29.00,L*值低而b*值高于陕西苹果,说明果肉色泽偏黄。质构仪测得江苏苹果的脆度显著高于陕西苹果。感官评价结果显示江苏苹果具有硬性低、易碎、易嚼、酸度低的特点,而多汁性和甜度差异不显著。在偏爱性比较中,73.7%的评价人员偏爱陕西苹果的色泽,而对滋味和质地的偏爱程度差异不显著。研究结果将为江苏富士品质评价提供借鉴。     

Determination of the Sensory Characteristics of Rose Apples Cultivated In Thailand

ABSTRACT:  Rose apple, an economic fruit in Southeast Asia, has potential as an export to western countries where its special attributes are better known to consumers. This research studied sensory characteristics of 8 rose apple varieties using highly trained panels and a defined sensory lexicon. A total of 9 sensory attributes including rose apple identity (ID), fruity, overall sweet, overall sour, bitter, firmness, cohesiveness of mass, astringent, and pulpy residue were present in all rose apple samples, but at different intensities for each variety. Only 5 attributes (floral/perfumy, green, spongy, initial crispness, and sustained crispness) were found in most samples, and were absent in a few samples; and "characteristic" attributes (rose, peel like, spicy, woody, earthy, starchy, and mealy) were detected in only 1 or a few samples. Based on their sensory characteristics, the rose apples being examined were categorized into 3 clusters. Rose apples in this study that are popularly cultivated and consumed including Pet-Num-Ping, Toon-Klao, Tub-Tim-Jun, Pet-Sai-Rung, and Pet-Sam-Pran, all of which were grouped together in cluster 3. They all had a crispy texture, but were very bland in flavor. Ma-Meow (cluster 1) and Num-Dok-Mai and Sa-Rak (cluster 2), which are not as popular, did not have a crispy texture; however, they did have the characteristic flavors of floral/perfumy and rose. The rose apples in cluster 3 might become better accepted if they had the flavor notes similar to those in cluster 1 and 2.     

An apple a day: the influence of memory on consumer judgment of quality

Regular consumers of apples are subjected to a high level of variability in sensory experience. This is due to the biological variation between individual apples, and the deterioration in quality that occurs when fruit are stored for many months. Therefore consumer assessment of quality is likely to be strongly influenced by their capacity to remember past experiences. In this study, we examined the ability of untrained participants to detect differences in apple texture (a primary determinant of quality for many consumers) when presented with fruit at daily and ∼1 min intervals. Each day the participants were given an apple that differed in firmness (measured by an instrumental puncture test) by 0, 5, 10, or 15 N from the fruit tasted on the previous day. They were asked whether the apple was harder, the same or softer than the previous apple, and how sure they were of their answer. The results were analysed using a traditional, bipolar, and weighted bipolar R-index. When comparing apples eaten at daily intervals, the participants were able to detect differences in texture when the instrumental firmness of the fruit differed by as little as 5 N (note that consumers might experience apples between ∼50 and ∼85 N during the year). When the participants tasted apples at ∼1 min intervals, they experienced difficulty detecting any difference in texture even when instrumental firmness of the fruit differed by as much as 15 N. The poorer performance of participants at ∼1 min presentation intervals may be explained by the disruption of a memory trace for texture by other similar but interfering memories (i.e. factors akin to ‘proactive interference’ and ‘suffix’ effects found in research on visual and acoustic memory).     

A review of acoustic research for studying the sensory perception of crisp,crunchy and crackly textures

The relationship that acoustic sensations have with the perception of texture has been studied for crisp, crunchy and crackly products. This has involved evaluating the contribution of chewing sounds to the perception of these textures or recording noises produced during mastication and evaluating various acoustic parameters from the resulting amplitude–time curves. Combining the analysis of acoustic recordings with mechanical testing results has been successful for predicting crispness and crunchiness of snack foods. The next stage for acoustic research should be to relate the structure of the products to the sounds produced during mechanical breakdown of the products in order to fully understand the textural properties of the food.     

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.     

苹果发育过程中细胞壁代谢及果肉质地的变化

以质地存在差异的“蜜脆”、“嘎拉”、“倭锦”、“鸡冠”4 个品种的苹果为材料,分析了果实发育过程中硬度、脆度和单果质量的变化,以及细胞壁中果胶、纤维素、半纤维素的含量和多聚半乳糖醛酸酶（polygalacronase,PG）、果胶甲酯酶（pectinmethylesterase,PME）、纤维素酶（carboxymethycellulase,Cx）、β-半乳糖苷酶（β-galactosidase,β-Gal）活性的变化,以期找到品种间质地差异的主要因素。结果表明：果实发育过程中果实硬度降低、脆度变小、感官脆度增大,细胞壁各个组分的含量在4 个品种中均呈下降趋势;在成熟果实中,脆性较好的品种果实中纤维素含量较低,水溶性果胶（water soluble pectin,WSP）含量较高,硬度低的品种果实中离子结合果胶（ionic soluble pectin,ISP）含量较高;PG、β-Gal在高脆品种“蜜脆”、“嘎拉”中活性较高,而Cx、PME活力在各品种间无明显差异。认为WSP、ISP和纤维素含量的差异以及PG和β-Gal活性的差异是形成苹果果实质地差异的关键因素。     

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.     

Changes in texture,cellular structure and cell wall composition in apple tissue as a result of freezing

Apple texture is one of the critical quality features for the consumer. Texture depends on several factors that are difficult to control and which change with freezing. To better understand the mechanisms involved in the texture degradation of apple tissues following freezing/thawing, our approach was to combine mechanical properties, cellular structure and cell wall composition measurements on fresh and thawed apples (Granny Smith) after three different freezing protocols (at ?20 °C, ?80 °C and ?196 °C). This work highlighted the interest of applying macrovision and image texture analysis to quantify the freezing effects on cellular structure and ice crystal size. Freezing at ?20 °C and after immersion into liquid nitrogen were the protocols affecting the most fruit texture leading to cell membrane breakage resulting in cell wall collapse and tissue breakage, respectively, which accounted for the mechanical behaviour of the samples. All freezing protocols induced vacuole burst showing that the turgor pressure preservation remains critical during the freezing process.     

Next target for food hydrocolloid studies: Texture design of foods using hydrocolloid technology

Texture is important in terms of both food palatability and the safety of eating. Recently, the importance of texture has been emphasized for the development of nursing-care foods, including dysphagia foods, in recent aged society, where the number of patients with mastication and swallowing difficulties is increasing. Texture design of these food products is now one of the most important tasks in the food industry in Japan. Texture of these food products should be optimized by modulating viscoelasticity using hydrocolloids so that they can easily transform to ‘ready-to-swallow’ bolus during oral processing. This article reviews the importance of texture as an essential attribute of foods and also the usefulness of hydrocolloids as an ingredient to modify and control food texture. The article also covers recent trials by the author’s research team on bolus rheology and in vivo acoustic analysis. The trials are to find some objective parameters describing the mastication and swallowing eases as an alternative to conventional bulk rheology and subjective sensory analysis.     

1-Methylcyclopropene postharvest treatment and their effect on apple quality during long-term storage time

The aim of this study was to evaluate the effect of the postharvest treatment by 1-methylcyclopropene (1-MCP) and storage time on the apple physicochemically quality. The effects of apple storage during 6 months on basic parameters such as dry weight, total soluble solids and titratable acidity, composition of phenolics, antioxidant activity and sensory evaluation were studied to evaluate the potential applicability of long-time stored apples for consumption and processing. Long-time storage of apples resulted in a higher dry matter but decreases total soluble solids and titratable acidity in all examined cultivars (cv.) of apples. The total phenolics determined by HPLC in fresh apples ranged from 1,243 mg in ‘Idared’ cv. to 1,435 mg/kg in ‘Shampion’ cv. During storage, the decrease of polyphenolic content has been observed, in ‘Shampion’ cv., it was higher than in ‘Idared’ cv. Similar effects were observed for antioxidant activity. Comparing quality of fruits just after harvest, it was found that cultivar affects most of the investigated sensory attributes with the exception of ripe apple smell, crispness, crunchiness and the overall texture score. In general, ‘Shampion’ cv. apples got higher ranks for sweetness, taste and the overall quality, whereas ‘Idared’ cv. were perceived as sourer, which is in arrangement with instrumental measurements. The results of presented study demonstrate that apples after storage, especially ‘Shampion’ cv., can be a valuable sensory attributes for food product and consumption. This study indicates that the use of 1-MCP treatment in long-term storage of apples is promising for maintaining the eating quality of fruits, however, in some extent may affect their antioxidant compounds content.     

Relationships between rheological properties, texture and structure of apple (Granny Smith var.) affected by blanching and/or osmotic dehydration

The objective of this work was to evaluate and correlate rheological properties (small-scale dynamic oscillatory and creep/recovery measurements and large-scale compression force-deformation testing), texture (sensory evaluation by trained panel) and structure (optical and transmission electronic microscopy observations) of apples osmotically dehydrated to water activity (a _w) 0.97 with glucose, with or without previous blanching. All apple samples showed a solid behavior (G′?>?G″) dominating the viscoelastic response, but both dynamic moduli were reduced due to processing. The instantaneous elastic compliance (J ₀) and the retarded compliances (J ₁ and J ₂) increased for treated tissues and the steady-state viscosity (η _N) was approximately 15% to 29% of the value of fresh apple. In general, compression parameters decreased for all treated tissues. Changes in structural features were mainly evidenced in heated samples. Partial least squares regression analysis regression models revealed that texture could be well predicted by rheological properties (compression and creep parameters). Juiciness, crispness and sensory hardness were negatively correlated to J ₀, J ₁ and J ₂, and η _N was negatively correlated to sensory fracturability. Some mechanical parameters (fracturability, hardness 2, area 2, modulus of deformability and cohesiveness) were positively related to sensory fracturability, crispness and sensory hardness; and juiciness was negatively correlated to hardness. Compression and creep parameters showed ability to evidence structure differences (rupture of membranes, swelling of cells and degradation of cell walls) and to explain texture of treated apples.