Food & Function
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A holistic approach towards defined product attributes by Maillard-type food processing Cite this: Food Funct., 2013, 4, 1105 Tomas Davidek,a Silke Illmann,a Andreas Rytzb and Imre Blank*a
A fractional factorial experimental design was used to quantify the impact of process and recipe parameters on selected product attributes of extruded products (colour, viscosity, acrylamide, and the flavour marker 4-hydroxy-2,5-dimethyl-3(2H)-furanone, HDMF). The study has shown that recipe parameters (lysine, phosphate) can be used to modulate the HDMF level without changing the specific mechanical energy (SME) and consequently the texture of the product, while processing parameters (temperature, moisture) impact both HDMF and SME in parallel. Similarly, several parameters, including Received 27th February 2013 phosphate level, temperature and moisture, simultaneously impact both HDMF and acrylamide Accepted 21st April 2013 formation, while pH and addition of lysine showed different trends. Therefore, the latter two options DOI: 10.1039/c3fo60080g can be used to mitigate acrylamide without a negative impact on flavour. Such a holistic approach has www.rsc.org/foodfunction been shown as a powerful tool to optimize various product attributes upon food processing.
Introduction Experimental Materials Extrusion is a versatile process for manufacturing of numerous foods which permits in one step several operations such as Rice our (Remy Industries N.V., Leuven-Wijgmaal, Belgium); conveying, mixing, cooking, texturing and shaping to be per- calcium carbonate (Brenntag Schweizerhall, Basel, Switzer- formed.1,2 Low labour, low energy and oor requirements are land); monosodium phosphate (anhydrous, >98%), disodium some of the advantages of extrusion.2 However, there are still phosphate (anhydrous, >98%) (Thermphos International BV, some challenges linked to extrusion cooking and avour Vlissingen, The Netherlands); L-lysine HCl (>99%) (Aminolabs, generation is one of them. Short residence time and aroma Hasselt, Belgium); L-rhamnose monohydrate (>99%) (Kaden Bio-chemicals, Hamburg, Germany); 4-hydroxy-2,5-dimethyl- Published on 20 May 2013. Downloaded by RSC Internal 02/07/2013 16:10:38. stripping at the die are o en pointed out as the main reasons for the less intense avour of extruded products.3–6 Another 3(2H)-furanone (HDMF, 99.6%) (Givaudan, Dubendorf,¨ 13 challenge is to modulate avour without negatively impacting Switzerland); C2-HDMF (isotopic purity >99%) (Aroma Lab, other product attributes, such as colour, shape, texture, nutri- Planegg, Germany); methanol (>99.9%) (Merck, Darmstadt, tive value or product safety. Germany); methyl acetate (99.5%), sodium sulphate (anhy- A holistic approach based on an experimental design and drous, >99%) (Fluka, Buchs, Switzerland). global product characterisation may be very useful to better understand the impact of recipe and processing parameters on Extrusion trials the avour of extruded products and, at the same time, on the The trials were performed on a BC 21 extruder (Clextral, Fir- other product attributes contributing to the overall product miny, France) using a rice our based model recipe. These trials quality. systematically varied 3 recipe parameters and 4 extrusion The aim of our study was to illustrate the benet of such a parameters: holistic approach by evaluating the impact of selected recipe Rhamnose : lysine molar ratio (1 : 0, 3 : 1) and extrusion parameters on different product attributes pH (6.4, 7.7) generated in a model rice recipe enriched with rhamnose. The Phosphate level (0.035, 0.134 mol kg 1) investigated attributes include colour, viscosity, acrylamide Way of precursor addition (dry mix, slurry) level, and the level of the caramel smelling 4-hydroxy-2,5- Moisture (17, 20, 23%) dimethyl-3(2H)-furanone (HDMF). Rhamnose, a 6-deoxyhexose, Screw speed (300, 400, 500 rpm) is a well-known precursor of HDMF.7–10 Temp./extruder length (120 C/700 mm, 120 C/500 mm, 135 C/500 mm, 150 C/500 mm).
aNestl´e Product Technology Center Orbe, 1350 Orbe, Switzerland. E-mail: imre. All possible combinations of these 7 parameters would lead 4 2 1 [email protected]; Fax: +41 244427021; Tel: +41 244427532 to 576 trials (¼ 2 3 4 full-factorial design). A fractional factorial bNestle Research Centre, 1000 Lausanne 26, Switzerland design over 32 trials was used in order to reduce the
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experimental effort without compromising on the quality of the a 250 mm 4 mm i.d. CarboPac PA100 anion exchange column results (Table 1). Rhamnose (0.9%) and lysine were either added (Dionex) and a 50 mm 4 mm i.d. CarboPac PA100 guard as such into a dry mix (dry addition) or were dissolved in water column (Dionex). Isocratic separation using water (A) and NaOH and injected into the extruder (slurry preparation). The extruded (100 mmol L 1, B) was achieved as follows: 88% A and 12% B as a products were dried in a Minimat ZIBO M oven (Wiesheu, Ger- mobile phase at a ow rate of 1 mL min 1 for 18 min. Each many) and milled in a MGI-628 mill (Frewitt, Switzerland). analytical cycle was followed by cleaning and regeneration of the column with NaOH (1 mol L 1) for 5 min and equilibration of the column with initial conditions for 10 min. L-Rhamnose was Rhamnose analysis quantied with an electrochemical detector equipped with a gold Ground product (2 g) was suspended in hot water (75 mL, 70 C) working electrode. The electrode pulse potentials were as follows: ¼ – ¼ – ¼ and extracted (30 min) in a volumetric ask (100 mL). Aer the E1 0.1 V, 0 400 ms; E2 2.0 V, 410 420 ms; E3 0.6 V, 430 ms, ¼ – extraction, the volume of the extract was adjusted to 100 mL E4 0.1 V, and 440 500 ms. To increase the sensitivity, the with water, ltered through a double layer lter (Acrodisc PF column eluent was mixed with NaOH (300 mmol L 1,0.5mL Syringe Filters, 0.8/0.2 mm/25 mm) and analysed by High- min 1) prior to the detection. Quantication was based on a Performance Anion-Exchange Chromatography (HPAEC). calibration curve by comparing the peak area with that of stan- Quantitative data were obtained using a calibration curve. dard solutions containing known amounts of pure compounds. HPAEC analyses were performed on a Dionex ion chroma- Each sample was injected twice (variation coefficient <3%). The tography system (DX500, Dionex, Sunnyvale, CA) composed of an solutions and eluents were prepared using ultra-pure deionised autosampler (model AS-50 with a 25 mL sample loop), a gradient water (specic resistivity 18.2 MU cm) from a Milli-Q-system pump (model GP-50) with on-line degas, an electrochemical (Millipore, Bedford, MA). NaOH solutions used as eluents were detector (model ED-40) and a post column pump (HPLC Compact prepared by diluting a carbonate free 50–52% (w/w) NaOH solu- Pump, Bischoff, Germany). The separation was accomplished on tion in water previously degassed under vacuum.
Table 1 Fractional factorial design for preparation of extrudates
Rha : Lysa Phosphate Moisture Screw speed Extruder Way of Sample # pH (mol/mol) (mol kg 1) % (rpm) Temp. ( C) lengthb additionc
A01 6.4 1 : 0 0.035 17 500 150 Short Dry A02 6.4 1 : 0 0.035 20 400 120 Long Slurry A03 6.4 1 : 0 0.035 20 400 120 Short Slurry A04 6.4 1 : 0 0.035 23 300 135 Short Dry A05 6.4 1 : 0 0.134 17 500 120 Short Slurry A06 6.4 1 : 0 0.134 20 400 135 Short Dry A07 6.4 1 : 0 0.134 20 400 150 Short Dry Published on 20 May 2013. Downloaded by RSC Internal 02/07/2013 16:10:38. A08 6.4 1 : 0 0.134 23 300 120 Long Slurry A09 6.4 3 : 1 0.035 17 400 150 Short Slurry A10 6.4 3 : 1 0.035 20 500 120 Long Dry A11 6.4 3 : 1 0.035 20 300 120 Short Dry A12 6.4 3 : 1 0.035 23 400 135 Short Slurry A13 6.4 3 : 1 0.134 17 400 120 Short Dry A14 6.4 3 : 1 0.134 20 500 135 Short Slurry A15 6.4 3 : 1 0.134 20 300 150 Short Slurry A16 6.4 3 : 1 0.134 23 400 120 Long Dry A17 7.7 1 : 0 0.035 17 400 120 Long Slurry A18 7.7 1 : 0 0.035 20 300 150 Short Dry A19 7.7 1 : 0 0.035 20 500 135 Short Dry A20 7.7 1 : 0 0.035 23 400 120 Short Slurry A21 7.7 1 : 0 0.134 17 400 135 Short Dry A22 7.7 1 : 0 0.134 20 300 120 Short Slurry A23 7.7 1 : 0 0.134 20 500 120 Long Slurry A24 7.7 1 : 0 0.134 23 400 150 Short Dry A25 7.7 3 : 1 0.035 17 300 120 Long Dry A26 7.7 3 : 1 0.035 20 400 150 Short Slurry A27 7.7 3 : 1 0.035 20 400 135 Short Slurry A28 7.7 3 : 1 0.035 23 500 120 Short Dry A29 7.7 3 : 1 0.134 17 300 135 Short Slurry A30 7.7 3 : 1 0.134 20 400 120 Short Dry A31 7.7 3 : 1 0.134 20 400 120 Long Dry A32 7.7 3 : 1 0.134 23 500 150 Short Slurry
a b c Rha ¼ L-rhamnose, Lys ¼ L-lysine. Short ¼ 500 mm, long ¼ 700 mm. Dry ¼ precursors (rhamnose and lysine) were dry mixed into the feedstock, slurry ¼ precursors were dissolved in water and injected as a slurry.
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Analysis of HDMF Data analysis
Ground product (1 g) was suspended in cold water (50 mL), The fractional factorial design allowed quantication of the 13 1 spiked with 150 mL of internal standard ( C2-HDMF; 3 mgmL main effects of the 7 investigated parameters in an independent of methanol) and extracted for 1 h using a magnetic bar stirrer. way, thanks to its underlying orthogonal structure.13 All main Aer the extraction and sedimentation for 30 min, the extract was effects appeared to be signicant on the a ¼ 5% signicance ltered through a PURADISC 25 PP (polypropylene, 0.45 mm/ level. The statistical analyses were performed using NCSS.14 25 mm) and a double layer lter (Acrodisc PF Syringe Filters, 0.8/ Main effects were visualized using bar charts: each bar 0.2 mm/25 mm). A SPE cartridge ENVI-Chrom P was rinsed rst represents the difference between the mean of all samples with methanol (3 mL), then with water (2 mL) and nally loaded produced at a given level of a parameter (e.g. pH 6.4) and the with the sample extract (2 mL) containing the internal standard. overall mean. The cartridge was rinsed with water (2 mL) and dried for at least 30 min under vacuum (ca. 35 mbar). Aer drying, the HDMF and Results and discussion internal standard were eluted with methyl acetate (2 mL). The eluent was dried over anhydrous sodium sulphate, and imme- Thirty two extrudates prepared according to a fractional facto- diately analysed by GC/MS. If the analysis could not be performed rial design were subjected to analysis of residual rhamnose, ff the same day, the eluent was stored in a freezer ( 80 C). HDMF, acrylamide, colour, and viscosity. The main e ects were GC-MS analyses were performed on a Finnigan Trace gas calculated for each attribute to quantify the impact of individual ff chromatograph coupled to a Finnigan Trace mass spectrometer recipe and extrusion parameters on di erent product attributes. (both ThermoQuest, Italy) equipped with a MPS2 autosampler The advantage of this approach consists in the comparison of ff (Gerstel, Switzerland). The separation was achieved on a the main e ects obtained for individual parameters which ZebronWAX capillary column (30 m 0.25 mm, lm thickness permits us to easily identify critical recipe/process parameters 0.25 mm, Phenomenex, USA) using helium as a carrier gas with a driving the given product attribute. The higher is the absolute ff constant ow of 2 mL min 1. Samples were introduced via value of the main e ect the bigger is the impact of the indi- splitless injection at 240 C(1mL). The oven temperature vidual recipe/process parameter on the product attribute program was 40 C, 2 min, 40 C min 1, 120 C, 6 C min 1, studied. 185 C, 10 C min 1, and 240 C, 10 min. The temperature of the ion source was 200 C. Mass spectra in the EI mode were Impact of recipe and extrusion parameters on the residual level of rhamnose generated at 70 eV over a mass range of 30 to 220 Da. Quanti- cation of HDMF was performed in the scan mode by The main effects inuencing the impact of individual parame- measuring the molecular ions of HDMF (m/z 128) and that of ters on the residual rhamnose level are shown in Fig. 1. 13 the internal standard C2-HDMF (m/z 130). All samples were analysed in duplicate (variation coefficient < 8%).
Published on 20 May 2013. Downloaded by RSC Internal 02/07/2013 16:10:38. Colour analysis
This was performed on a ColorFlex spectrophotometer (Hunt- erlab, USA) according to the standardized principle of the CIE- LAB L*a*b* system.11
Viscosity measurement
The powder (21 g) was reconstituted in 170 mL of preheated milk ( 70 C) and the viscosity was measured with the Rapid visco analyser RVA-4 (Newport scientic, Warriewood NSW, Australia). The measurement was done for 10 min at 50 C and with a constant shear rate of 50 min 1. The maximum of viscosity reached within the 10 min (maximum pap viscosity) was extracted from the curve.
Acrylamide analysis
Ground samples (2 g) were spiked with 100 mL of internal 13 1 standard ( C3-acrylamide; 5 mgmL ) suspended in hot water (60 C, 10 mL), vortexed (1 min), and sonicated in an ultrasonic water bath (5 min). Aer precipitation of proteins with Carrez reagents, the extract was further cleaned up by solid-phase extraction and the acrylamide content was determined by LC- Fig. 1 Main effects of recipe/process parameters on the residual rhamnose level 12 MS/MS as described previously. expressed as % of the original level.
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The rhamnose degradation was affected by almost all importance for HDMF formation, the temperature had much parameters investigated, with the exception of screw speed higher impact on acrylamide formation as compared to other which had only a marginal impact. Its degradation increased two parameters. Hence, the use of high temperatures (>140 C) with increasing pH, increasing temperature, increasing phos- should be avoided as these temperatures have a stronger effect phate level, decreasing moisture content, and with lysine on acrylamide formation than on HDMF formation. addition. The extrusion temperature had the highest impact Similarly to rhamnose degradation, the screw speed had only followed by moisture in the extruder. marginal impact on the formation of both compounds. These data are in line with those reported by Parker et al. who observed Impact of recipe and extrusion parameters on the levels of negligible impact of screw speed on avour of oat extrudate.10 HDMF and acrylamide Contrary to the level of phosphate, the other two recipe parameters (pH and addition of lysine) did not show the same The addition of rhamnose into the feedstock should lead to the trend on the formation of HDMF as compared to acrylamide. generation of HDMF, a desirable compound smelling caramel- While pH had no effect on HDMF, the acrylamide level like. On the other hand, it might also trigger the formation of decreased with decreasing pH value. The effect of lysine is even undesirable compounds, such as acrylamide, through interac- more interesting as the addition of lysine enhanced the yield of tion of reducing sugars with asparagine present in the rice our. HDMF while decreasing the level of acrylamide. These results In this context understanding of the critical recipe/process not only conrm literature data15 concerning the impact of pH parameters that drive the formation of individual compounds is and amino acids on generation of acrylamide, but also of crucial importance to favour the formation of desirable demonstrate that lowering of pH and the addition of amino compounds while mitigating those that are undesirable. acids represent an interesting mitigation option that may have The comparison of the main effects is shown in Fig. 2 indi- neutral or even positive impact on avour. cating the impact of recipe and process parameters on the levels Overall, the addition of lysine had the most signicant of HDMF and acrylamide. impact on the generation of HDMF as the yield of HDMF Several parameters, including phosphate level, temperature generated upon extrusion was 7 mol% higher in the presence of and moisture, showed a similar trend on HDMF and acrylamide lysine as compared to in its absence. formation. Consequently, if these parameters are used to enhance HDMF formation from rhamnose, the acrylamide Impact of recipe and extrusion parameters on colour levels will be increased as well. Nevertheless, the order of importance of these three parameters was not the same for The inuence of the process parameters on colour development HDMF and acrylamide. While all three parameters had similar is displayed in Fig. 3. The colour intensity of the samples Published on 20 May 2013. Downloaded by RSC Internal 02/07/2013 16:10:38.
Fig. 2 Main effects of recipe/process parameters on yield of HDMF and level of acrylamide.
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phosphate level, increasing temperature and decreasing mois- ture content. These factors also increased HDMF formation. Contrary to the HDMF formation, the darkness was also affected by pH, screw speed and the way of precursor addition, i.e. it increased at higher pH, low screw speed and dry addition of precursors. Thus, these parameters can be used to modulate the colour of products without affecting the HDMF level. For example, if the colour change should be limited then lower pH should be applied to convert rhamnose into HDMF.
Impact of recipe and extrusion parameters on viscosity of the pap
The viscosity of the reconstituted product strongly varied depending on the parameters used (maximum viscosity found in the range from 71 to 4973 mPa). It was mainly affected by temperature, moisture, and the extruder length (Fig. 4). The viscosity increased with increasing temperature and moisture and decreasing extruder length, which can be explained by the decrease of SME. Although the viscosity is highly depen- dent on SME not all the parameters that affect SME also affect the viscosity and vice versa. For example, the screw speed had a strong effect on SME but a negligible effect on viscosity. On the other hand, the way of precursor addition and pH had no effect Fig. 3 Main effects of recipe/process parameters on colour. on SME, but it affected the viscosity. The effect of pH could possibly be explained by the increased hydrolysis of starch increased (the L* value decreased indicating a darker sample molecules at lower pH. In general, the inuence of the above and the a* and b* values increased indicating increased redness mentioned parameters on viscosity is very high and needs to be and yellowness, respectively) with lysine addition, increasing taken into consideration when optimizing avour development. Published on 20 May 2013. Downloaded by RSC Internal 02/07/2013 16:10:38.
Fig. 4 Main effects of recipe/process parameters on maximum pap viscosity and specific mechanical energy (SME).
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Conclusions 4 L. J. Bruechert, Y. Zhang, T.-C. Huang, T. G. Hartman, R. T. Rosen and C. T. Ho, J. Food Sci., 1988, 53, 1444– This study has shown that the combination of different process 1447. parameters and ingredient composition allows modulation of 5 H. I. Hwang, T. G. Hartman, M. S. Karwe, H. V. Izzo and individual product attributes (e.g. colour, avour) upon food C. T. Ho, in Lipids in Food Flavours, 1994, pp. 144–157. processing and optimizing conditions with respect to other 6 J. M. Ames, R. C. E. Guy and G. J. Kipping, J. Agric. Food attributes (e.g. texture, mitigation of undesirable compounds). Chem., 2001, 49, 4315–4323. Among others it has been shown that addition of amino acids 7 P. E. Shaw and R. E. Berry, J. Agric. Food Chem., 1977, 25, 641– can be used to enhance avour while mitigating acrylamide. A 644. holistic approach based on an experimental design combined 8 T. Doornbos, G. A. M. van den Ouweland and S. B. Tjan, Prog. with global product characterisation may lead to rapid product Food Nutr. Sci., 1981, 5,57–63. optimisation via understanding of key parameters driving 9 P. Schieberle, in Flavour Precursors – Thermal and Enzymatic individual product attributes and identication of relationships Conversion, 1992, vol. 35, pp. 164–174. between attributes. The holistic approach, as shown in this 10 J. K. Parker, G. M. E. Hassell, D. S. Mottram and R. C. E. Guy, paper, is complementary to the targeted approach based on J. Agric. Food Chem., 2000, 48, 3497–3506. labelling experiments, which allow monitoring of formation 11 R. W. G. Hunt, Measuring Colour, 1987. pathways upon food processing and identication of key 12 R. H. Stadler, F. Robert, S. Riediker, N. Varga, T. Davidek, precursors and intermediates of sensory active compounds. S. Devaud, T. Goldmann, J. Hau and I. Blank, J. Agric. Food Chem., 2004, 52, 5550–5558. Notes and references 13 R. L. Mason, R. F. Gunst, and J. L. Hess, Statistical design and analysis of experiments with applications of engineering and 1 H. P. Schuchmann, in Lebensmittelverfahrenstechnik – science, 1989. Rohstoffe, Prozesse, Produkte, 2005, pp. 189–218. 14 J. Hintze, NCSS 2007, Kaysville, Utah, http://www.ncss.com, 2 W. E. Riha and C. T. Ho, in Process-Induced Chemical Changes 2006. in Food, 1998, pp. 297–306. 15 P. Rydberg, S. Eriksson, E. Tareke, P. Karlson, L. Ehrenberg 3 W. L. P. Bredie, G. M. Hassell, R. C. E. Guy and D. S. Mottram, and M. Tornqvist,¨ J. Agric. Food Chem., 2003, 51, 7012– J. Cereal Sci., 1997, 25,57–63. 7018. Published on 20 May 2013. Downloaded by RSC Internal 02/07/2013 16:10:38.
1110 | Food Funct., 2013, 4, 1105–1110 This journal is ª The Royal Society of Chemistry 2013