The Importance of knowing your Medium: Ice Cream

Introduction:

                Ice cream (I/C) seems to be one of the simplest things to make, but due to the functional role of each ingredient it becomes very complex. Ice cream is a foam, because it contains around 50% air once frozen (Myhrvold 2011).  Making a stable foam can be difficult at times, but with patience and knowledge of your ingredients it can be done (Myhrvold 2011). Ice cream is defined as a foam and in Modernist Cuisine, foam is defined as gas-in-water emulsion (Myhrvold 2011). This is somewhat true for I/C, but I/C is truly an oil-in-water emulsion (Migoya 2008).

 

Ice cream is a frozen mixture of milk fat, emulsifiers, stabilizers, sweeteners, milk solids, and optional flavorings. Milk fat will provide creaminess and richness to the ice cream, and will also contribute to the melting characteristics (Milk Facts 2013). Sources of milk fat include milk, cream, and butter. Emulsifiers are used to keep the fat evenly distributed throughout the base during freezing and storing (Milk Facts, 2013). Egg yolks and mono/di-glycerides are used as emulsifiers in ice cream. If egg yolks are used they will contribute 33% of their weight to the amount of fat in ice cream. Stabilizers are used a lot in commercial ice cream production. They are usually proteins or carbohydrates that help to prevent small ice crystals from migrating to other ice crystals and forming larger crystals that would cause a coarse texture in the ice cream (Milk Fat 2013). The migration of ice crystals usually occurs during long-term storage, thus the reason why commercial ice cream producers need to use stabilizers (Milk Fats 2013). Sweeteners provide the characteristic sweetness of ice cream, but it also lowers the freezing point of the I/C. The sweetener will make sure that some of the water will be unfrozen at serving temperatures, thus making the I/C soft (Milk Fats 2013). If too much sweetener is added, the ice cream will be too soft. This solidifies the need for balance between all ingredients. The total amount of all the solids include the fat, protein, lactose, and any other solids included in the recipe (Milk Fat 2013). The solids will stabilize the air which was incorporated during the freezing process.  The outstanding qualities of cream were heightened when ice cream was created. Ice cream was first made by placing a container of the cream in snow or ice, but it was noticed that the snow or ice would turn to slush before the cream was frozen (McGee 2004). The “chemical ingenuity” of sprinkling salt on the snow or ice would allow the salt to dissolve into the snow, causing the freezing point of the snow to decrease (McGee 2004). 

The use of salts in freezing was first recorded in the 13^th century Arab culture, and along with many other things, the knowledge of salt was brought to Europe through the trade routes and crusades (McGee 2004). The first recipe to resemble ice cream was brought from the Far East in the early 13^th century by Marco Polo on one of his trading journeys (IDFA 2013). Other early uses of flavored, frozen ice going all the back to 2^nd century B.C. have been described, but none seemed to contain cream (IDFA 2013). Ice cream, in its beginning stages, seemed to only be enjoyed by the

privileged and those that could afford the luxuries of frozen ice. Alexander the Great and King Solomon were both known to be fond of flavored snow and ice (IDFA 2013). The ice was flavored with various things, some of which being honey and nectar (IDFA 2013). During the reign of the Roman Empire (A.D. 54-86), Nero Claudius Caesar was known to send runners into the mountains to gather snow, which would then be flavored with fruits and juices (IDFA 2013). The Italians and English seemed to discover “cream ice” at around the same time and it is hard to tell who was the first (IDFA 2013). After Marco Polo introduced the recipe he had discovered in the Far East, 300 years later it was than transformed into something we recognize as ice cream in the 16^th century (IDFA 2013). Ice cream was commonly seen on the table of Charles I in England, in the 17^th century (IDFA 2013).

 

                The modern methods of making ice cream have grown to many new heights. The use of high-quality ice cream machines, liquid nitrogen, dry ice, paco jets, and other modern equipment have caused ice cream to be a very pleasing, smooth delicacy. Also, the method, aging, freezing, overrun, and hardening of ice creams all play significant roles in the texture, flavor, and mouth feel of the “cream ice” (CS:Rsch Mthds 2013). In a previous lab, we tested the different methods of freezing on a lemon sorbet and produced varying results, but the data suggested that the ice cream machine and liquid nitrogen produced the better texturally good sorbet. Because the freezing time was quick on both methods, they produced very small ice crystals which gave them a very smooth texture. The class was split 50/50 between the liquid nitrogen and I/C machine. The other methods tested were dry ice and granita method. The paco jet was not used for that lab, but was used for the experiment that this lab report is based on. Aging of ice cream promotes two important things to happen. The first is the absorption of emulsifiers, which is where the lecithin from the egg yolks absorb to the surface of the fat globules and makes them more susceptible to partial coalescence (Ice Cream Science 2013). Partial coalescence occurs when the base is frozen, during

 

which the fat globules (coated in lecithin) connect and form a fat matrix where air and ice are trapped (Ice Cream Science 2013). The second role that aging has is the crystallization of fat. When the ice cream base is cooled to below 4^oC during aging, the fat droplets begin to crystallize (Ice Cream Science 2013). Full crystallization of fat is needed for the coalescence of fat globules, and the aging of the ice cream base increases the rate of crystallization (Ice Cream Science 2013). Freezing is when base is frozen as quickly as possible, while being continuously agitated in order to incorporate air, reduce crystal size, and create more surface area (McGee 2004). This will, if done correctly, create a very smooth texture. Overrun happens during freezing, it is when the incorporation of air causes an increase in volume (McWilliams 2012). This increases in volume is coined ‘overrun’. The hardening stage is the last stage of the ice cream making process. When the ice cream base is brought to around -6^oC in the ice cream machine, it is then stopped and then extracted and placed in a hardening cabinet for a recommended 2 hours (McGee 2004). The hardening stage must happen quickly, because when the ice cream base first comes out of the freezing apparatus, only half of its water is frozen into ice crystals (McGee 2004). During hardening, another 40% of the water migrates onto the various ice crystals. If this step happens slowly, certain ice crystals will uptake more water than others, causing the ice cream to have a coarse texture (McGee 2004).

                This experiment was conducted to show the different effects of using the recommended minimum and maximum ingredient weights in different ice cream bases. The ice cream bases were evaluated on ice crystal size, sweetness, flavor release, and mouth feel. This experiment was used to show what happens when the ingredients are used at their extremes, and to demonstrate the importance of having a balance of all the ingredients. In our experiment, there was a total of 10 variations of I/C, but my team was in charge of producing the minimum and maximum fat variations. The other variations include: minimum and maximum sugar, minimum and maximum solids, and a second set of minimum and maximum fat. The chart used to determine these percentages was taken out of Chef Migoya’s book Frozen Desserts:

Table 1: Chef Migoya's Table of Min's and Max's (Migoya 2008)

Ingredient:	Min	Max
Fat (from milk, heavy cream, butter, egg yolks, and other dairy products)	3%	14%
Stabilizers	0.3%	1%
Emulsifiers	0.2%	0.3%
Non-Fat Solids: Include all solids, even those found in dairy, minus the fat. Remember, solids can be found in egg yolks)	15%	30%
Total Solids: includes the above plus all fats	25%	51%
Liquid	100% minus solids	100% minus solids
Sugar (sweetening strength, is the addition of all sugars, solid and liquid) A variety of sugars can be used.	16%	24%
Egg Yolks	7%	9%
Flavors	2%	10%

 

Materials and Methods:

                All ingredients for the recipes produced were scaled out using an Escali Primo Scale Model# P115 (Burnsville, MN). The ice cream base was heat with a DIPO induction burner (IB) Model TCK35-A, thermo probe included (Troy Ohio). The temperatures were recorded using a PT03 digital thermometer Model #TS71 (Guangdong, China). The I/C bases were cooked in a 4 qt. CIA All-Cad sauce pot. The I/C bases were stirred during the cooking process using a CIA issued 10” whisk. The bases were strained through a CIA issued chinois into the aging containers.  Our team aged our I/C bases in Camsquares-Camwear containers (Huntington Beach, CA) and Pacojet metal containers (Zug, Switzerland). The I/C was churned in a Carpignani Model # LB-100B (Winston Salem, NC) and a Pacojet (Zug, Switzerland). The ice cream base then underwent its hardening stage in the Culinary Science blast freezer.

                The recipes for the two variations of minimum and maximum fat are in Table 2 below:

Table 2: Formulas for Min and Max Fat from Team 1 and Team 4

Ingredients	Team 1 – 3% Fat	Team 1 – 14% Fat	Team 4 – 3% Fat	Team 4 – 14% Fat
Milk Powder	317 g	215 g	259 g	97.9 g
Sugar	400 g	320 g	340 g	340 g
Yolks	140 g	140 g	160 g	140 g
Whole Milk	367 g	813 g	170 g	920 g
Heavy Cream	-	512 g	-	502 g
Skim Milk	776 g	-	1061 g	-
Vanilla Bean Paste	10 g	10 g	10 g	10 g

The formulas were developed using Chef Francisco Migoya’s ice cream formula, which can be found in his book Frozen Desserts (Migoya 2008). For the production of all the bases, the milk/cream was placed in a pot onto the induction burner on medium-heat, setting 3. At 25^oC/77^oF, the milk powder and vanilla were added and the mixture was whisked constantly. At 35^oC/95^oF, the egg yolks and sugar were added at this time and the mixture was continuously whisked until the sugars had dissolved. The mixture should be whisked constantly in order to prevent curdling or sticking on the bottom of the pot. At 45^oC/113^oF, the heavy cream was added (Team 4 placed their heavy cream in the pot at the beginning of the method to see if there was a difference). The mixture was then brought to 85^oC/185^oF and it was held at this temperature for 3 minutes in order to pasteurize and homogenize the mixture. The mixture was then passed through the chinois and chilled to 4^oC/39^oF as quickly as possible using an ice bath, stirring the mixture periodically.  Once chilled, the viscosity was taken of each base with a #5 Zahn Ladle. Each variation was then divided into two pacojet containers (818 g for 14% and 805 g for 3%) and were allowed to age for 24 hours. Half of team 4’s base was place in two 2 qt. cambro containers, for aging, because half of team 4’s base was churned in the traditional I/C machine. The bases were made on a Wednesday and were then place in the freezer on Thursday afternoon (except for team 4’s second half). The bases were then sheared in the pacojet the following day and team 4’s second half was churned in the Carpignani. They were allowed to harden in the freezer for 1.5 hours. Then the ice creams then evaluated. They were evaluated based on their mouth feel, fat coating, crystal size, flavor release, sweetness, and appearance. Also, a melting test was performed by placing a CIA issued temme onto a tabletop lined with plastic wrap. Then three scoops of each variation were placed onto the tamis and timed until all the I/C had melted through the tamis.

Results:

                The viscosities of the bases prior to aging a freezing are as follows in Table 3:

Table 3: Viscosity of Team 4's Variations

 

	1st Rep:	2nd Rep:	3rd Rep:	Mean:
14% Fat:	6	6.1	5.9	6
3% Fat:	14.9	14.1	14.8	14.6

The 14% fat base was the thinner of the two bases, which was surprising since it contained more fat. The 3% was the thicker of the two bases, but showed to have the largest ice crystals when frozen.

The results of the tasting of all the variations are included in Table 4 below:

Table 4: Qualitative descriptors of I/C variations (*highest preference)

	Ice Crystal Size:	Sweetness:	Flavor Release:	Mouth feel:	Appearance:
Max Sugar	Large crystals	Extremely Sweet	Not very much flavor release	Extremely ‘cliding’, sugar is overpowering	Very Soft, liquid around the edges of the container
Min Sugar	Small-medium	Sugar is detectable, but noticeably overpowering	A lot better in comparison to max, vanilla detected	Disappears very quickly in mouth	Frozen completely
Max Solids	Small-medium	Very sweet	Low flavor release	Chalky, malty flavor	Frozen, but scoop able
Min Solids	Small-medium	Very sweet	Low flavor release	Chalky, drying sensation, malty	Frozen, but scoop able
T1 Max Fat*	Very small	balanced	Good flavor release	Fat coated top of mouth, rich, vanilla detected	Good appearance, stable, scoop able
T1 Min Fat	Medium-large	Very sweet,	not very good flavor release, due to high sugar	Large crystals, too sweet to detect	Spongy appearance, most overrun of all bases
T4 Max Fat	Small-medium	balanced	Good flavor release, vanilla detected	Good mouth feel, fat coated top of mouth	Good, not much melting
T4 Min Fat	Large	balanced	Bad flavor release	Very icy	Melting quickly
T4 Max Fat Churned*	No Ice Crystals Detected	Balanced	Great flavor release, vanilla detected	Smooth, fat coated mouth and disappeared quickly	Frozen, but scoop able
T4 Min Fat Churned	Very Small	balanced	Ok flavor, slightly sweet, vanilla detected	Smooth	Frozen, but scoop able

The results suggested to be very interesting. The most interesting of all was team 4’s variations and the differences between the churned and pacotized bases. The churned bases were much smoother and had much smaller ice crystals than the pacotized bases. As expected, the max sugar was very soft and the min sugar was hard. The min and max solids were very similar, which suggested something might have gone wrong in formulations.

                The melting time of ice creams were as follows in Table 5:

Table 5: Melting test of Team 4's variations

Minutes:	3% Variation	14% Variation
2:00	Start of Drips	Start of Drips
3:20	Steady drips, matted appearance	Slower melting, very shiny
8:25	Slow drips	Speed of drips increasing
12:00	Fully Melted	Fully Melted

At the beginning of the test it seemed as though the 3% was going to melt much quicker, but it slowed later in the test and the 14% base sped up, which caused them to finish melting at the exact same time.

Discussion

                One of the main things observed in this experiment, is that the formula is there as a guideline and without proper knowledge of the ingredients and the skills to perform, the recipe will not turn out the way you want it.  The differences between variations of Team 1 and 4 were greatly noticeable, even though they both were the same fat percentages. The slight differences in recipes produced totally different foams or ice cream. All variations from all the teams seemed to lack the finesse and luxurious qualities of good I/C, but this is the effect of using the ingredients at their extreme amounts. This served as a demonstration of what could happen when certain ingredients are used in excess or insufficient amounts.

                The viscosity differences in the two variations were interesting and unexpected. The 3% fat variation had much more skim milk than the other, so it was automatically assumed that it would have a lower viscosity. The 14% was much thinner, almost 9 points seconds faster through the Zahn. The theory for this is thought to be because of the higher amount of milk powder and yolks in the 3% fat variation. The 3% fat variation contained 1% more yolks and 8% more milk powder than the max fat.

                The churned and pacotized ice creams came out extremely different. The churned I/C was a much more smooth and delicate I/C. This is thought to be because of what happens in the i/c machine that is not happening in the pacojet. The pacojet is does not have ice cold walls, even though the bases are frozen, the blades of the pacojet are causing friction, which in turn causes heat. The rise and fall of temperature in the bases is believed to be the cause of the larger ice crystals. The ice cream machine did not cause this because it had the refrigerated walls which kept the ice cream base cold at all times and brought it down in temperature and not up.

                The max sugar variation was extremely soft and this is because there was too much sucrose in the base and mixture. “Ice cream is basically made up of little ice crystals and air bubbles and fat droplets, all sort of glued together by a viscous sugar solution" (Clarke 2004). Sugar lowers the freezing point of the water in the base, and it will keep a portion of this base liquid or soft when frozen. This is why if too much sucrose is added the I/C will be too soft.

                There are two things that occur during the meltdown of ice creams: the melting of ice crystals and the collapse of the fat-stabilized structure (Food Science 2013). The melting of the ice crystals is fully dependent on the ambient temperature of the environment (Food Science 2013). Even after the ice crystals have melted, the fat matrix is dependent on the extent of partial coalescence that occurred during aging and freezing of the I/C base (Food Science 2013). This is mainly affected by the concentration of emulsifiers in the base (Food Science 2013). An egg yolk contains about 22% lecithin (Palacios 2005). Lecithin was the main emulsifier in our variations, and our 3% fat base had about 4.4 grams more of lecithin than the max fat variation. My theory for why the 3% was able to hold out for 12 minutes (Table 5) is due to the higher amount of lecithin and the much higher amount of milk powder. My theory for why the 14% I/C didn’t start melting at a faster pace, is because of the higher amount of fat in the base, which probably caused for much more partial coalescence to happen during aging and freezing. This caused the 14% fat I/C to have a much stronger fat matrix and once it collapsed at around 8 minutes (Table 5) it began to melt much faster.

Conclusion:

                In our experiment we realized the great importance of knowing the role each ingredient plays in a recipe. The uses of the ingredients have to be known in order to produce a product that is desired. We used ice cream as an example for this lab, but in truth, the knowledge gained from this experiment can be used in many different applications.

                Ice cream is a very enjoyable and pleasant food to eat, though it may seem simple, it is one of the most complex foods the average consumer eats. To get a desirable ice cream, there are many factors that affect its outcome; ingredients and amounts, method, aging, freezing, overrun, hardening, and storing of the base are the most important. They all contribute something in order to provide a smooth frozen dessert that has been enjoyed for centuries.

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