Crunchiness: Incisor Blade or Multiple Puncture Probe
Batter produces a crisp, golden, flavourful crust. The primary factor in sensory acceptance of batter is crispness, a property manifested as a tendency to yield suddenly with a characteristic sound when subjected to an applied force. Consequently, when crisp products such as battered chicken are tested using a Texture Analyser, their force-time curves display characteristic peaks and drops in force ranging from large and few peaks for a very crunchy product to small and many for a product with more delicate crispness. Wherever the product’s crispness lies within this range, the force-time curve is jagged with multiple peaks when tested in bulk.
 |
| Typical test using the Multiple Puncture Probe |
Penetration testing is well-suited to the measurement of battered products as it is possible to measure the properties of the battered layer by penetrating through the batter into the bulk. Very crisp products may be tested using probes with a smaller contact area such as a 2mm penetration probe or incisor blade, also known as the Volodkevich Bite Jaw. This fixture performs an imitative test by simulating the action of an incisor tooth biting through food with upper and lower jaws, with the biting action provided by the compressive movement of the upper jaw shearing into the test sample.
The greatest advantage of using this fixture is its close imitation of the biting action that occurs in the mouth. However, there are two limitations: the sample size is limited to 1cm2, and samples need to be supported by the fingers until the upper jaw comes into contact with the sample.
The Multiple Puncture Probe is a better alternative to single penetration in many cases, as it allows manufacturers to test nonuniform products containing particulates of different size, shape, structure and levels of hardness, to provide repeatable results, due to the averaging effect of the multiple penetration pins. Battered chicken strips are an excellent example of this product type, as the chicken shapes and battered layer are non-uniform. Outer pins may be removed so that the area covered by pins is optimised for the sample in question, with all the pins fitting within the perimeter of any given sample in a batch.
Compression testing is also frequently used in the measurement of batter crispness, particularly when measuring samples with a soft, compliant core or batter samples on their own. Forces are magnified in compression when using larger probe contact areas.
 |
| Testing chocolate biscuits using the Acoustic Envelope Detector |
When analysing a graph measured from the penetration of a sample such as battered chicken, the number of peaks produced represent the fracture events that have occurred during the test. Counting the number of force peaks, the average drop-off and measuring linear distance are common calculations applied to such curves.
The Acoustic Envelope Detector can by employed for any material which produces an audible noise when tested as it captures another dimension (i.e. sound) during the test which can also be analysed and used as a measured product feature. This is usually for acoustic analysis testing of brittle materials and the acoustic signal is as a result of a crack, break, snap or failure of some type. Batter crispness is well suited to acoustic data analysis.
Published research examples that use this test:
- – Defatted rice bran (DRB) is a by-product in the rice bran oil industry generated in large quantities. Unfortunately, DRB, is underutilised and often discarded despite containing valuable proteins, minerals, dietary fiber, and bioactive phytochemicals. This study examined the effects of four DRB substitution levels (0, 10, 15 and 20% of mixed flour in batter and pre-dust) on fried chicken nugget properties. Scientists from Kasetsart University used their TA.XTplus Texture Analyser to measure batter crispness by penetration testing.
- – Deep-fried battered and breaded coatings provide foods with texture, flavour, reduced moisture loss and oil uptake. The physical characteristics of deep-fried batter and breadcrumb coatings was investigated for deep-fried prawns by researchers from the University of Birmingham. Breadcrumbs were divided using different sieve sizes and then applied to the coating in order to investigate the effect of breadcrumb size on the physical and mechanical properties. As crispness is a fundamental sensorial property of deep-fried battered products, crispness was evaluated by uniaxial compression to acquire mechanical and acoustical measurements simultaneously, using their TA.XTplus Texture Analyser. Results showed decreasing breadcrumb size reduced the number of multiple failures, reduced jagged appearance of the force profile was observed, reduced maximum compression force and acoustic emission, which has been used as a representative of crispness. This study provides evidence of the importance of breadcrumb size in deepfried battered and breaded formulations.
- – The aim of this study performed by Scientists from São Paulo State University was to identify the best combination of settings of a device coupled to a TA.XTplus Texture Analyser for acoustic analysis in order to find strong correlations with the sensory texture. Sensory attributes and instrumental properties’ strong correlations indicate that the texture analyser in combination with the acoustic envelope detector is a good instrument to mimic human mastication and texture perception, through both force and sound stimuli. This study about dry crisp food may contribute to the literature and food industry, as well to future studies about wet crispy and crunchy foods.
