The Effect of Milk Fat Percentage on Milk Gummy Snacks

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1 Whitney Heavrin F&N 453 Food Chemistry The Effect of Milk Fat Percentage on Milk Gummy Snacks Abstract: The idea of a milk snack was conceptualized and to see what would make the best product, different milk fat % levels were used. The first trial failed to gel while in the dehydrator so gelatin was added to make a more gelled product. When tested in the water activity machine and the texture analyzer as well as against a sensory panel, the findings were that the product with the softest texture was the product with the 0% milk fat level and panelists liked the flavor of the 0% and 2% milk fat level products. This tells us that the 0% milk fat would be the most desirable to the consumer and would be a good replacement for a roll-up snack made with fruit juice. This new product contributes protein and calcium to American diets which would be great since Americans as a whole are not getting enough calcium. Since the lowest fat product is what would be used, this allows both adults and children to use the milk snack to replace another gummy product and get nutritional value from it. Introduction: Roll-up gummy snacks made with fruit are a common lunch-time food. To use this concept and make a product similar but with a nutritional benefit was the basis for the design of this experiment. Milk is a nutritious part of our diet and dairy is one of our food groups (USDA). It is known that the American population, especially children and teens, does not get enough calcium in their diets. According to an article in Food Technology (Ohr), 30% of children ages 1-5, 70% of preteen girls, 60% of preteen boys, 90% of teenage girls and 70% of teenage boys are not meeting the calcium needs for their bodies. To combine the idea of a gummy roll-up snack with the nutrition of milk would be very beneficial but presented several hurdles to overcome. When using milk in a product, rancidity and microbial growth were large concerns and since this product is meant to be shelf-stable, was even more important. Also with milk, Maillard browning, and the pigment melanoidin, were almost certain considering the

2 presence of sugar in the forms of natural lactose and added sucrose, and also the protein in the milk. The product was dried in a food dehydrator which heated the product and removed water, both of which are catalysts to the Maillard browning reaction (Scheule and Bennion). It was important that the color of the snack be in keeping with the chosen flavor and to make sure this browning did not negatively affect the perception by the taste panel. For this reason, chocolate was the flavor of choice and cocoa was medium used to deliver that flavor as to add both the natural flavor and color that could mask the color caused by melanoidin as a result of the Maillard reaction. This was not a huge concern because often, milk products are added to confectionary creations to produce this very same reaction for the subtle caramel notes that are produced (Clark). In addition to flavor, it was desirable to have a soft and chewy texture to the product. It was determined that the product would not form a gel on its own after the first trial and gelatin was added for its gelling properties. The amount of gelatin used was determined as 8.5% of the weight of the milk. This is actually not the correct usage level for gelatin so the product had a different texture than it should have. The calculation is as follows. 200g x.085 = 17g: this was added to the recipe (seen in methods). To determine the hardness, flavor and shelf-stability of the product, the testing methods that were used include texture analysis, water activity and sensory panels (Duxbury). According to research, fat can be very important in a confectionary product, as it can help add softness to a product as well as mouth feel (Pszczola, 2004). This added confidence to the experiment that the independent variable, which was milk fat percentage,

3 was going to be critical in the outcome of the product in the case of texture and taste panel preference. This experiment was designed to find two things. The first thing was if the product idea would actually work with or without gelling agents and the second thing was if the percent milk fat used made a difference in the texture and palatability of the product. Methods: This experiment used a gummy snack recipe from a Purdue professor who used it in an introductory processing class. It was changed slightly and the ending result is the recipe below. 200g milk (0%, 2% or 3.7%) 65g granulated sugar 35g corn syrup 15g cocoa powder 17g gelatin The ingredients were weighed out and the dry ingredients were sifted together to get rid of lumps and to make the cocoa easier to dissolve in the milk. This mixture was added to the milk and beat with a whisk until mixed. The corn syrup was added last so that it didn t bind to water before the dry ingredients were added and it was also beat in with a whisk. This procedure was repeated for all three fat percentage levels for each of the three trials. Prior to the mixing of the ingredients, the dehydrator was prepared. This involved lining the three trays with Glad Press-n-Seal wrap and then cutting a hole in the middle where the air travels through. Also, the trays were heavily sprayed with a flavorless canola oil cooking spray. Before each sample was poured, the try was placed on the dehydrator so that once poured, the sample did not have to be moved and risk spillage or leakage.

4 When all three samples were placed in the dehydrator, it was turned on and left to sit for 24 hours to dry. The dehydrator only had one setting so no air temperature or convection speed is known. After 24 hours, the dehydrator was turned off and the product left to sit and continue to gel for at least 12 hours after. When finished, the product was removed for testing. The sensory panel filled out a structured ranking scale for hardness and a rating scale for flavor. The panelists were given a variety of samples that came from different parts of the product with some being thicker and some being thinner. The sensory score card is as follows. The product was also tested for water activity and texture. Two uniform pieces of the product were placed in the disposable testing container for the water activity machine and left to be tested. Each sample was tested in duplicate. For the texture analyzer, the machine was put on the gelatin setting and two pieces of the product were stacked for testing. The cone probe was used to test puncture force. This was tested in triplicate around different areas of the product as to get an accurate reading.

5 Sensory Evaluation Please taste each sample in front of you. On the scale below please mark the line that best describes each gummy snack 502 Very Soft Slightly Soft Slightly Hard Very Hard Extremely Soft Moderately Soft Neither Soft or Hard Moderately Hard Extremely Hard 239 Very Soft Slightly Soft Slightly Hard Very Hard Extremely Soft Moderately Soft Neither Soft or Hard Moderately Hard Extremely Hard 797 Very Soft Slightly Soft Slightly Hard Very Hard Extremely Soft Moderately Soft Neither Soft or Hard Moderately Hard Extremely Hard Rank the samples in order of preference. 1 being the one you like most and 3 being the one you like least. Comments:

6 Results: Trial 1 did not produce a gel and therefore was not able to be tested for water activity or texture because it would not release from the wrap covering the dehydrator trays. Table 1. Water activity for each product containing a different milk fat percentage: Trial 2. Milk Fat % Aw Avg Table 2. Water activity for each product containing a different milk fat percentage: Trial 3. Milk Fat % Aw Avg Table 3. TA force for each product containing a different milk fat percentage: Trial 2. Milk Fat % Force (g) Avg

7 Table 4. TA force for each product containing a different milk fat percentage: Trial 3. Milk Fat % Force (g) Avg Table 5. Subjective analysis of the hardness of each product containing different milk fat percentages. The scale was 1-9, 1 being very soft and 9 being very hard. Trial 2. Milk Fat % Subject: Avg Table 6. Subjective analysis of the hardness of each product containing different milk fat percentages. The scale was 1-9, 1 being very soft and 9 being very hard. Trial 3. Milk Fat % Subject: Avg Table 7. Subjective analysis of the flavor of each product containing different milk fat percentages. The scale was 1, 2 or 3, 1 being the flavor they liked the most and 3 being the flavor they liked the least. Trial 2. Milk Fat % Subject: Avg / /

8 Table 8. Subjective analysis of the flavor of each product containing different milk fat percentages. The scale was 1, 2 or 3, 1 being the flavor they liked the most and 3 being the flavor they liked the least. Trial 3. Milk Fat % Subject Avg Water Activity vs Milk Fat % Water Activity (Aw) Milk Fat (%) Figure 1. Water activity levels compared among the different fat % levels. Trial 2.

9 0.7 Water Activity vs Milk Fat % 0.6 Water Activity (Aw) Milk Fat (%) Figure 2. Water activity levels compared among the different fat % levels. Trial TA Force vs Milk Fat % TA Force (g) Milk Fat (%) Figure 3. TA puncture force among the different % fat levels. Trial 2

10 1800 TA Force vs Milk Fat % TA Force (g) Milk Fat (%) Figure 4. TA puncture force among the different % fat levels. Trial Hardness vs Milk Fat % 6.2 Hardness (1-9 scale) Trial 2 Trial Milk Fat (%) Figure 5. Hardness according to subjective tests compared among to different fat % levels. Trials 2 and 3.

11 2.5 2 Flavor Preference vs Milk Fat % Trial 2 Trial 3 Preference (1-3 scale) Milk Fat (%) Figure 6. Flavor preference according to subjective tests compared among to different fat % levels. Trials 2 and 3. Discussion: One important factor in this experiment was the ability to make it shelf stable. This can be done in many ways but on is lowering the water activity of the product so that microbial growth is inhibited. This requires an Aw <.85. From the values in Tables 1 and 2 you can see that all of the products at all fat levels were far below this level (Fellows, 2003). This would suggest that the product is extremely shelf stable. In fact, the product was still intact, fresh tasting and had good texture after 3 weeks in a container permeable to oxygen. This was not part of the experiment, but is worth noting. When looking at Figures 1 and 2, you will note the comparison of the average water activity for each fat percentage level for both trials. We would expect that a product like this, with a high dairy content that there will be bacterial production and in a lower fat product, less bacterial can survive which suggests less respiration and this ultimately leads to a lower water activity reading (O Connor, 2000). Figure 2 clearly shows that this is the case since the sample with 3.7%

12 milk fat has a higher Aw than the sample made with 2% milk fat and that that sample is higher than the sample made with 0% milk fat. However, in Figure one, this is not as clear to see with the sample made with 3.7% milk fat as it is lower than the rest. It is not that much lower when you see that the separation between that and the sample with 0% milk fat is.04, or 4% water. From this, we would assume that the lower fat content would also produce a harder product from having little water or fat to soften it. This however, was not the case. As can be seen in Table 3 and 4, the 0% milk fat produces the softest product that is easiest to puncture. The reason for this could be that more water was in the product initially and so more was there to evaporate. This could have led to a thinner product which would be perceived as softer since there was less product thickness to get through. When looking at Figures 3 and 4 it can be seen the results were the same for both trials. The other two samples seem to fall where it was expected for them to fall in softness. As was said in the introduction, however, too much gelatin was used and if a smaller percentage of gelatin had been used, the results would be more clear and easier to determine. In terms of hardness of the products, the sensory panel had the same feelings about the products. In Tables 5 and 6 and figure 5 it shows that the product with 0% milk fat was perceived to be the softest, the product with 3.7% milk fat was the next softest and the 2% milk fat product was the hardest to the sensory panel. This makes it obvious that something is going on at a molecular level. It seems that the 2% milk fat product had the right combination of fat and water available to form a very strong gel. The most important thing to the consumer however, is flavor. In Tables 7 and 8 and in Figure 6 you can see that the sensory panel didn t really have a preference between the

13 2% and 0% milk fat samples. However, they preferred both of these to the 3.7% milk fat sample. From a nutritional point of view, I feel that since the 0% milk fat sample is softer, has less fat, and is similar in taste preference as the 2% milk fat sample, it would be the optimum product to go to market. This product is also thinner, replicating more closely, this concept of a roll-up gummy snack. Consumers are crazy about low fat and no fat products, especially when they have a nutritional value. In the future, I would suggest some modifications to this procedure and also add some sophisticated measuring techniques. The gelatin is the first thing that needs to be changed. 8.5% was too high and produced a product that was tough and chewy. I would also see how this changes the flavor preference because I hypothesis that the gelatin is trapping the cocoa flavor and not allowing it to release as quickly. In addition, as the process of making the product is occurring, it would be nice to measure the temperature, convection speed and moisture content of the air inside the dehydrator so that later, if the product were to be moved into mass production, theses variables could be better controlled for a more consistent product.

14 References: Clark, J.P Crystallization is Key in Confectionery Processes. Food Technology, Vol. 58, No. 12: pg Duxbury, D Measuring Food Texture. Food Technology, August 2005: pg Fellows, P J. Food Processing Technology; 2 nd ed. CRC press and Woodhead Publishing Limited O Connor, P. Fenelon, M. A. Guinee, T. P. The Effect of Fat Content on the Microbiology and Proteolysis in Cheddar Cheese During Ripening. Journal of Dairy Science Vol 83 Pg Ohr, L.M Nutraceuticals and Functional Foods. Food Technology, Vol. 58, No. 4: pg Pszczola, D.E Confectionery Ingredients Bridge Indulgence with Health. Food Technology, Vol 56, No. 9: pg 72. Pszczola, D.E Confection: A Sweet Acronym. Food Technology, Vol 86, No. 10: pg Scheule, B. and Bennion, M. 2000, Introductory Foods. Columbus, OH. Prentice Hall. pg 109. USDA. Inside the pyramid.