Comparison of ultrasonic and pulsed NMR techniques for determination of solid fat content

An ultrasonic technique was developed to study the crystallization process of edible fats on-line. A chirp wave was used instead of the conventional pulser signal, thus achieving a higher signal-to-noise ratio. This enabled measurements to be made in concentrated systems [~20% solid fat content (SFC)] through a 8.11-cm thick sample without significant signal loss. Fat samples were crystallized at 20, 25, and 30°C at a constant agitation rate of 400 rpm for 90 min. The crystallization process was followed by ultrasonic spectroscopy and a low-resolution pulsed nuclear magnetic resonance spectrometer. Specific relationships were found between ultrasonic parameters [integrated response, time of flight (TF), and full width half maximum] and SFC. TF, which is an indirect measurement of the ultrasonic velocity (v), was highly correlated to SFC (r 2 > 0.9) in a linear fashion (v = 2.601 SFC + 1433.0).Paper no. J10957 in JAOCS 82, 305-312 (May 2005). KEY WORDS:Full width half maximum, integrated response, p-NMR, solid fat content, time of flight, ultrasonic velocity.Sensing and measurement of food properties is crucial to the improvement of the quality of food and profitability of food manufacturing operations. Instrumental measurements can reduce the dependence on time-consuming chemical and sensory analysis. Measurements should provide some information about the food (e.g., temperature, composition, structure, concentration) that will be useful in controlling final product quality. The response time is crucial, so although laboratory tests on finished product are valuable, measurements made on-line of the freshly made or in-process foods are better. On-line sensors used in the food industry must also be inexpensive and robust to survive in the frequently hot and wet environment of a food-processing plant. The technique should also be both nondestructive and amenable to hygienic design principles (ideally, noninvasive). It should also provide a relatively simple output to an operator or an automated control system (1). Ultrasonic technology has advantages over many techniques because it can be applied to systems that are optically opaque, concentrated, and electrically nonconducting. In addition, ultrasonic measurements are rapid and precise, are nondestructive and noninvasive, can be fully automated, are nonhazardous, and are particularly suitable for on-line monitoring.Ultrasound techniques exploit the interaction of high-frequency sound with matter to generate information about material physicochemical properties. Such techniques have been established and used in numerous fields such as medicine, oceanography, and materials science. A number of publications have demonstrated the usefulness of ultrasound in food research, including particle size determination, creaming, crystallization, and aggregation phenomena in emulsions (2,3). Ultrasound also has been used to characterize the rheological behavior of solid fat dispersions and xanthan/sucrose mixtures (4,5) and to calculate the percentage of frozen material in foods...

Section: Resultssupporting

confidence: 93%

mentioning

confidence: 99%

In situ monitoring of solid fat content by means of pulsed nuclear magnetic resonance spectrometry and ultrasonics

Martini

Bertoli

Herrera

et al. 2005

“…The relative differences persisted in the attenuation data and were larger, but they were not seen in the reflectance measurements. Other workers have seen differences in velocity in more concentrated dispersions not related to changes in SFC (16). Although it is possible that some of these differences were due to polymorphic transitions, it is also possible that differences in the crystal-crystal interactions, which become more significant at higher solids loadings, may have led to some structural sensitivity of ultrasonic velocity in more concentrated systems.…”

Section: Resultsmentioning

confidence: 93%

Shear and longitudinal ultrasonic measurements of solid fat dispersions

Saggin

Coupland

2004

Dispersions of coating fat in corn oil (2.5-12.5 wt%) were prepared following two different protocols: Type A dispersions had an average crystal size of 30-36 µm, whereas type B dispersions were less than 1 µm. In both dispersions the fat crystals were aggregated into larger structures (up to 80 µm). The longitudinal ultrasonic properties (i.e., velocity, attenuation, and reflectance) were linearly related to the solid fat content, but only attenuation was sensitive to the different microstructures. The velocity and reflectance measurements were modeled using the Urick equation. Shear ultrasonic reflectance and oscillatory viscometry were used to measure the dynamic viscosity of all dispersions. According to both methods, type B samples were always more viscous than type A at a similar solids content. The correlation between the two techniques was good (r 2 > 0.99), but the numeric agreement was different for both systems.

“…Ultrasound techniques have been used in numerous areas, such as medicine, oceanography, and materials science. Several authors have described the application of ultrasonic waves to the determination of SFC in fat systems (3)(4)(5)(6)(7)(8)(9). Ultrasonic technology has advantages over many other techniques because it can be applied to systems that are optically opaque, concentrated, and electrically nonconducting.…”

mentioning

confidence: 99%

New technologies to determine solid fat content on‐line

Martini

Herrera

Marangoni

2005

The determination of solid fat content (SFC) is an important analytical procedure in the food industry. The most common way to determine SFC is by low-resolution pulsed NMR (p-NMR). Although this technique is very sensitive and easy to use, it has the disadvantage that it cannot be used for on-line measurements. The present work compares new technologies to determine SFC on-line. On-line ultrasonic spectroscopy and NMR-MOUSE (NMR mobile universal surface explorer) techniques were compared with off-line p-NMR measurements and there was a good correlation between the values obtained. Ultrasonic measurements accurately described the SFC variation, whereas NMR-MOUSE determinations need to be improved to some extent owing to a strong temperature and motion dependence. These two techniques can be used as on-line methodologies to determine SFC during the crystallization of fats. FIG. 3. (a) Calibration curve for the NMR-MOUSE technology showing the linear relationship between the NMR-MOUSE reading and the conventional pulsed NMR (p-NMR) technology, mq20 (shown as liquid percentage). (b) Comparison of SFC values of different dilutions of sample A measured by traditional p-NMR, mq20, and NMR-MOUSE (x and L L, respectively). For abbreviations see Figure 1. SOLID FAT CONTENT DETERMINATION ON-LINE 317 JAOCS, Vol. 82, no. 5 (2005) FIG. 5. Comparison between SFC values measured with traditional p-NMR, mq20 (line with no symbols), ultrasonics (L L), and NMR-MOUSE (L) for sample A (a) and B (b), diluted with 50% of canola oil crystallized at 30°C. For abbreviations see Figures 1 and 3.