Protection of Artificial Blueberry Flavor in Microwave Frozen Pancakes

Chapter 16

Downloaded by UNIV OF MICHIGAN ANN ARBOR on October 1, 2017 | http://pubs.acs.org Publication Date: March 24, 1995 | doi: 10.1021/bk-1995-0590.ch016

Protection of Artificial Blueberry Flavor in Microwave Frozen Pancakes by Spray Drying and Secondary Fat Coating Processes H u i Chin Li and Gary A . Reineccius Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108

While spray dried flavors were retained at about the same level as liquid flavors, fat coating of the spray dried flavor resulted in substantially better retention in pancakes. The improved retention of coated flavors during frying and microwave reheating is attributed to the delayed release of the flavor during heating. Flavor release from coated flavorings into water ranged from 23 to 68% when temperatures did not exceed the melting point of the coating fats, but increased to 80-98% when temperatures exceeded the melting points of the coating fats. This was dependent upon the material being coated (e.g. gum acacia vs maltodextrin) and type of coating fat. Flavor loss during frying and microwave reheating of pancakes ranged from 0-15% for coated flavorings as compared to 17-95% when liquid flavorings were used.

The market for microwave foods appeared to be unlimited a few years ago. However, sales never reached the predicted levels and in fact, have been declining in recent years. The main problem with microwave foods has been the lack of quality relative to their traditional counterparts. A n important aspect of quality is flavor. The major flavor problems associated with microwavable foods are a lack of typical flavor development during heating and substantial losses of any flavors added to the product (1). The first problem in attempting to increase the thermal generation of aromas during microwave heating has been addressed in several ways including the addition of precursor systems (2), the use of active packaging (metalized films) and/or formulation modification to improve absorption of microwave energy. The second problem, that of flavor loss during microwave 0097-6156/95/0590-0180$12.00/0 © 1995 American Chemical Society Risch and Reineccius; Encapsulation and Controlled Release of Food Ingredients ACS Symposium Series; American Chemical Society: Washington, DC, 1995.


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Artificial Blueberry Flavor in Frozen Pancakes 181

heating, is relevant since whatever flavor is formed during heating or added in an attempt to overcome a lack of flavor development is typically lost due to steam distillation. Studies have shown 95 % or more of a given flavor compound can be lost from model food systems during microwave cooking (3). Steiken et al (4,5) has investigated the influence of microwave heating on flavors. He found that the formation of Strecker aldehydes and the loss of flavor components were much greater during microwave heating than conventional heating. There are several techniques which may be used to improve the retention of flavor compounds during the microwaving process. Sadafian et al (6) have studied the retention of encapsulated aroma compounds during extrusion-cooking. Spray dry encapsulation and β-cyclodextrin inclusion were found to increase the aroma retention during extrusion. Reineccius (7) has discussed the potential for using secondary coating of already encapsulated materials in microwave food applications. Theoretically, this approach offers excellent protection to the flavoring during storage (little evaporative losses and oxidation) and would delay release until the flavoring is well into the microwave process thereby decreasing flavor losses. The secondary coating can be accomplished in several ways. Preferred methods include fluidized-bed coating (8) and centrifugal coating (9). The objectives of this research were to evaluate the effectiveness of spray dried flavorings and secondary coated spray dried flavorings in improving flavor retention during the initial frying and subsequent microwave reheating of pancakes. Experimental Model blueberry flavor. The blueberry model flavor system was composed of equal parts of ethyl methyl butyrate, α-terpineol, ethyl valerate, phenylenthanol, r-2-hexenal, anethole, linalool, methyl anthranilate, maltol and 7-decalactone. These chemicals were obtained from Aldrich (Milwaukee, WI). Spray drying. Gum arabic and maltodextrin-100 (M-100) were the two carrier materials used for spray drying. Solutions of gum arabic (30% w/w) and M-100 (50% w/w) were gently heated over a steam bath to facilitate solubilization. The solutions were cooled to room temperature and refrigerated (4°C) overnight. Model blueberry flavor was emulsified into the hydrated carriers (20% w/w of solids) using a high shear blender (Greerco Corp. model 1L.81, Hudson, NH). Each emulsion was immediately spray dried using a Niro Utility Drier with a centrifugal wheel atomizer. The inlet and outlet temperatures were controlled at 200 and 100°C, respectively. Secondary coating. The spray dried flavorings produced above were put into a fluidized bed agglomerator (Glatt Hlatgen WSG-5, Winchester, K Y . ) and coated with liquid fat by Zumbro Inc. (Owatonna, M N ) . Two commercial powdered vegetable stearins were used for coating: Dri-Tex and Stereotex (Karlshamns U S A , Inc., Columbus, OH). Dri-Tex is a hydrogenated cottonseed oil with a melting point of 145°F (62.8°C) and Stereotex is a hydrogenated soybean oil with a melting point of 165°F (73.9°C) . These powdered fats were melted prior to applying in the fluidized-bed. The desired coating of fat was ca. 30% by weight.

Risch and Reineccius; Encapsulation and Controlled Release of Food Ingredients ACS Symposium Series; American Chemical Society: Washington, DC, 1995.

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Determination of flavor release from coated flavors. 1 g of secondary coated powder was weighed into a headspace vial, and 9 ml of distilled water was added. The vial was sealed with a Teflon cap and then incubated at two controlled temperatures for 1 hr before manually sampling the headspace for flavor compounds by G C . For Dri-Tex coated powder, the incubation temperatures were 45 and 74°C. The Stereotex coated powders were incubated at 52 and 85°C. Values for a complete release (100%) were based adding 0.3 g coating fat and 0.7 g spray dried powder into a headspace vial and following the same procedure as outlined above for the coated samples. Determination of coating amount. 2 g of secondary coated powder were placed in an extraction thimble (Whatman, 22 x 80 mm) and covered with glass wool. The thimble had been predried and weighed. Extraction was done in a Soxhlet extractor with 150 ml petroleum ether for 6 hr. The thimble was removed and dried in an air oven at 100°C for 1 hr. The thimble was placed in a desiccator with Drierite and allow to cool. The thimble and its contents were weighed to calculate the fat content in the sample and the percent fat in the sample was calculated. Determination of flavor retention in batter and fried pancakes. 20 g of spray dried flavoring were mixed with 300 g of commercial pancake mix. The flavored pancake mix was then combined with 300 g distilled water to make pancake batter. The flavored pancake batter was then fried on a Teflon coated griddle at 190°C until the color was golden brown. Samples of batter and fried pancakes were taken for the determination of blueberry flavor compounds and the remainder of the pancakes were frozen at -20°C overnight in Zip Lock bags. The following day, the frozen pancakes were reheated in a microwave oven and then analyzed for blueberry flavor compounds. Flavor isolation was done by solvent extraction. The procedure involved adding 30 ml acetone (containing ethyl hexanoate as internal standard, 0.045mg/m/) to 15 g batter, (15-x^ g fried pancakes, or (15-x ) g microwave reheated pancakes. Xj and x were corrections for water loss in the fried pancakes and microwave reheated pancakes, respectively. These amounts of water were added back to the sample prior to adding acetone. The extraction was completed on a magnetic stirplate. The resultant mixture was filtered and the filtrate frozen at -70 °C for 90 min to solidify the fat. The liquid portion was recovered by filtering. The extract was then dried with anhydrous magnesium sulfate, filtered again, and concentrated to approximately 2 ml under nitrogen and analyzed by GC. The G C , column and operating conditions were as follows: Hewlett Packard model 5880 with FID detector; DB-5 column (length:30m, i.d.:0.32mm, film thickness: 1 w, J&W Scientific, Folsom, CA). The GC temperature program started at 40°C and then increased at 5°C/min to 200°C. The carrier gas was helium at a column head pressure of 15 psig. 2

2

Results and discussion Efficiency of secondary coating. Table I shows the percentage of fat coated on the spray dried flavorings. The fat contents of the secondary coated powders were


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Artificial Blueberry Flavor in Frozen Pancakes 183

all ca. 30% which was the coating target. The standard deviations of four coated powders were low ranging from 0.7% to 3.7% for G-165 (Stereotex coating on gum arabic spray dried flavor) and M-145 (Dri-Tex coating on maltodextrin-100 spray dried powder), respectively. Table I. Percentages of fat on secondary coated spray dried flavorings* G-165"

G-145

M-145

w

M-165


% ....

30.88±0.21

28.06±0.64

27.61 + 1.02

28.79+0.22

**: indicates gum acacia carrier and 165°F coating. ***: Indicates maltodextrin carrier and 165°F coating. Thermal release. Due to the nature of the analytical headspace procedure, results were most accurate and reproducible with only the more volatile flavor compounds. Volatility of many of the flavor compounds in the model was too low to be detected by the static headspace procedure. Thus, data on flavor release from the secondary coated flavorings was based only on the release of the most volatile compounds, ethyl methyl butyrate(EMB) and ί-2-hexenal, which provided more reproducible data. It is expected that the release of all volatiles would be represented by these compounds. The percentages of flavor release of Dri-Tex coated flavoring at 45 and 74°C incubation are shown in Table II. The results show that when the incubation temperature is lower than the melting point of Dri-Tex (63 °C), release of the flavoring is retarded compared to the data from incubation at a temperature higher than that of the Dri-Tex melting point. It is, however, obvious that over a period of 1 hr at 45 °C, a substantial amount of flavoring was released even at the lower incubation temperature. This shows that the coating was not perfect but allowed some of the spray dried particle to dissolve and release its flavor upon contact with with water. When the incubation temperature was higher than the melting point of DriTex, the coating fat melted and the secondary coated powder dissolved in water to release flavor compounds quickly. If the incubation time is long enough, the flavor release of the dissolved powder should theoretically reach 100%. In this experiment, about 86% the of flavor release was obtained from both G-145 and M 145 samples. However, G-145 samples showed a better thermal flavor release than M-145. The percent changes between two incubation temperatures (45°C & 74°C) were ca. 62 and 35 for G-145 and M-145, respectively. Flavor release from Stereotex coated flavorings (Table III) was similar to that from Dri-Tex coated flavorings. The coated gum acacia powder released less flavor when held below the melting point of Stereotex than the maltodextrin coated powder. The percent changes between the two controlled temperatured samples (52°C and 85°C) were ca. 52 and 41 for G-165 and M-165, respectively. Flavor protection. Data for the losses of added blueberry flavor compounds during the frying of pancakes are presented in Table IV. When flavor was added



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ENCAPSULATION

before the frying process, compounds which are more volatile, such as ethylmethyl butyrate, ethyl valerate and ί-2-hexenal, should have greater losses than other less volatile compounds. Little loss was observed for fat soluble flavor compounds such as α-terpineol, maltol, anethole and γ-decalactone. Results of spray dried powder samples were mixed. The increases of ethylmethyl butyrate, ethyl valerate and γ-decalactone were not expected. A possible explanation for this abnormal phenomenon might be that the lipid oxidation products of the aged pancake mix and new volatiles formed during frying might coelute with these three compounds making chromatographic separation difficult. The higher flavor losses observed in spray dried samples vs. flavor solution samples was considered the result of longer frying time which caused greater volatilization of flavor compounds. Table II. Percentages of flavor release of Dri-Tex coated powder incubated at 45 and 74°C* % release M-145 45 °C EMB 54.15 f-2-hexenal 68.73 *: all experiments have four replicates.

74°C

G-145 45 °C

74 °C

84.25 88.11

22.90 26.76

88.63 80.31

Table III. Percentages of flavor release of Stereotex coated powder incubated at 52 and 85°C* % release M-165 G-165 85 °C 52°C 85 °C 52°C EMB ί-2-hexenal

49.31 55.49

91.03 98.50

32.50 39.11

88.35 88.09

With Stereotex coated powder samples, all the flavor compounds showed an increased after the frying process. The increases are reasonable because after the temperature of pancakes reached the melting point of Stereotex, the flavor compounds started to release into fried pancakes. During the frying process, the holding time at high temperature was just enough for the coating fat to melt and release the flavor compounds, but not long enough for flavor compounds to volatilize. Thus few flavor compounds were detected in the G-165 batter samples, but increased amounts of flavor compound were observed in G-165 fried pancakes. When frozen pancakes undergo microwave reheating, the flavor compounds typically flash out by steam distillation. Table V shows the losses of added blueberry flavor compounds in microwave reheated pancakes. Severe losses of flavor compounds were observed from both flavor solution and spray dried powder samples, particularly for E M B , ethyl valerate and f-2-hexenal. In G-165 samples, the losses of these three compounds were significantly reduced.


16. LI & REINECCIUS

Artificial Blueberry Flavor in Frozen Pancakes

Table IV. Changes of added blueberry flavor compounds in fried pancakes* solution**

G-spray**

G-165**


% EMB -69.0 ethyl valerate -86.0 r-2-hexenal -51.0 linalool -21.0 — phenylethanol cKerpineol -2.0 anethole -8.0 ~ methyl anthranilate γ-decalactone -11.0 : compared to batter samples. *: all experiments have four replicates.

+ 13.4 +27.1 -53.3 -56.1 -15.3 -47.9 -58.6 -22.2 +25.0

+ 117.0 +97.8 + 135.6 +94.5 + 137.3 + 113.2 + 119.7 +85.6 + 122.4

Table V. Changes of added blueberry flavor compounds in microwave reheated pancakes* solution**

G-spray**

G-165

-94.6 -94.9 -57.5 -62.0 -61.3 -16.7 -33.3 -28.4 -25.2

-41.6 -49.2 -10.0 -19.5 -14.2 -21.8 -31.5 -7.1 -14.3

1

% EMB -93.6 ethyl valerate -92.9 ί-2-hexenal -81.6 linalool -55.7 phenylethanol a-terpineol -30.6 anethole -32.6 — methyl anthranilate γ-decalactone -24.7 : compared to fried pancakes. **: A l l experiments have four replicates.

One interesting observation was the performance of methyl anthranilate in liquid flavor samples and encapsulated samples. Osnabrugge (9) has pointed out that alcohols, aldehydes and ketones will interact with proteins to varied degrees. With no protection, the amino group of methyl anthranilate reacted with the aldehyde group of the sugars in the pancake mix to form Schiff's bases. This binding of methyl anthranilate prevented extraction by acetone, so there was no peak observed for methyl anthranilate in flavor-solution samples. With protection by encapsulation, methyl anthranilate was separated from the sugars by the carrier wall material. The interaction was blocked, and we could again detect the peak of methyl anthranilate in G-spray and G-165 samples.


185

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ENCAPSULATION


Conclusion Thermally controlled release of flavor compounds is a characteristic property of secondary fat coated flavored powders, and can be applied in microwave frozen food products to protect against flavor loss from distillation (flash-out). The initial wall materials used as the spray dry carrier will affect the performance of secondary fat coated powders. In this study, the secondary coated gum arabic powder was observed to exhibit a better thermally controlled release property than the maltodextrin secondary coated powder. Many factors still need to be evaluated in the future, such as the protective effect of maltodextrin spray dried powders and secondary coated powders, as well as the physical properties of these encapsulated powders. A l l of these factors should be more thoroughly investigated before applying the theory to commercial food products. Acknowledgement Published as paper No. 21480 of the contribution series of the Minnesota Agriculture Experiment Station based on research conducted under project No. 18018. Literature Cited 1. Whorton, C. and Reineccius, G . A . , 1990, Flavor problems associated with the microwave cooking of food products, in "The Maillard Reaction in Food Processing, Human Nutrition and Physiology", ed. P . A . Finot, H . U . Aeschbasher, R . F . Hurrel and R.Liardon, Birkhäuser, p. 197-208. 2. IFF patent 4,735,513. 3. Risch,S.J., 1989, Flavors for microwavable foods, Cereal Food World, 34:226 4. Steinke, J.Α., Frick, C. Strassburger, K . J . and Gallagher, J., 1989, Interactions of flavor systems in the microwave environment, Cereal Food World, 34:330-332. 5. Steinke, J.Α., Frick, C . , Gallagher, J.A. and Strassburger, K . J . , 1989, Influence of microwave heating on flavor, in " Thermal Generation of Aromas", ed. T . H . Parliment, R.J. McGorrin and Chi-Tang Ho, American chemical Society, Washington, D . C . , pp. 519-525. 6. Sadafian, A . and Crouzet, J., 1988, Aroma compounds retention during extrusion-cooking, in" Frontiers of Flavor, Proceeding of the 5th International Flavor conference", ed. G. Charalambous, Elsevier Science Publishers B . V . , pp.623-637. 7. Reineccius, G . A . , 1989, Flavor encapsulation, Food Rev. International, 5(2):147. 8. Sparks, R . E . , 1981, in "Kirk-Othmer Encyclopedia of Chemistry Technology",Wiley, New York, pp471. 9. Sparks, R . E . , 1987,U.S. Patent 4,675,140 10.Osnabrugge, W . V . , 1989, How to flavor baked goods and snacks effectively, Food Technol., 43(1):74-82. RECEIVED October 11, 1994


Protection of Artificial Blueberry Flavor in Microwave Frozen Pancakes

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