How Long Does It Take For Ice Cream To Freeze

xiv MINUTE READ
The shelf life of food is dependent on changes in the microbial content, chemic nature (e.chiliad., flavour), and the concrete attributes of the product (Goff & Hartel, 2013). In ice foam, microbial growth does not occur to whatsoever significant extent during storage of either the mix or of the frozen product, so that physicochemical changes are more often than not considered the most important in determining shelf life (Goff & Hartel, 2013).

In this post, I'll discuss the physicochemical changes in water ice foam that impact shelf life.These volition include: ane. ice recrystallisation; 2. lactose crystallisation; 3. a change in the size of air cells; and four. changes in ice foam book, leading to a defect known as shrinkage. I'll offer tips for extending shelf life and then summarise the physiochemical changes at the finish.

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1. ICE RECRYSTALLISATION

Ice crystal size is a disquisitional factor in the development of smooth and creamy ice cream (Donhowe et al. 1991). Smooth and creamy ice foam requires the majority of ice crystals to be small, around 10 to xx µm in size. If many crystals are larger than this, the ice cream will exist perceived as being coarse or icy (Drewett & Hartel, 2007; Goff & Hartel, 2013).

Ice foam is frozen in two stages: dynamic and static freezing. Ice crystals are formed during dynamic freezing, where the ice foam mix is frozen and agitated in an ice cream machine to incorporate air, and grow during static freezing, where the partially frozen ice cream mix is hardened in a freezer without agitation. The principal aim is to promote the formation of as many small ice crystals equally possible during dynamic freezing and and so preserve these small crystals during static freezing and storage.

Ice recrystallisation (the full general increment in ice crystal size) during storage is considered to take the almost pregnant consequence on the shelf life of water ice cream because of the adverse issue on texture.

one.1. FACTORS AFFECTING ICE RECRYSTALLISATION

Numerous factors influence the rate of recrystallisation, including the freezing and hardening processes, storage atmospheric condition, and water ice cream composition (Hartel, 1998).

1.1.i. DYNAMIC FREEZING

Nucleation (the birth of ice crystals) occurs only during dynamic freezing where the temperature at the cold freezer bowl wall is cold enough to grade new crystals. The germination of smaller ice crystals and narrower initial ice crystal distribution during dynamic freezing generally lead to longer shelf life since the ice crystals must grow to a larger extent (Goff & Hartel, 2013). To read my discussion of the factors influencing ice crystal formation and growth during the freezing of ice cream, delight click hither.

1.1.two. STATIC FREEZING

No new ice crystals are formed during static freezing just the existing small crystals abound in size until the temperature decreases to -18°C (0.4°F), or ideally -25°C to -30°C (-ix.4 to -20.2°F), to halt this growth. During static freezing, water ice crystals typically grow by virtually xxx% to 40% (Marshall et al., 2003) to an average size of about 25 to 45 µm (Berger et al., 1972; Donhowe & Hartel, 1996; Hagiwara & Hartel, 1996; Koxholt et al., 2000; Sofjan & Hartel, 2004). A hateful ice crystal size of about 50 um is considered an boilerplate point where people get-go to notice coarse texture (Goff & Hartel, 2013).

Because higher temperatures accelerate recrystallisation, quick hardening to temperatures at or below -xviii°C (0.4°F) limits ice crystal growth (Donhowe, 1993; Hartel, 1996).

TIP#1 – QUICK HARDENING
To promote faster hardening of the partially frozen ice foam during static freezing, place your ice foam at the back of your freezer where it's ordinarily the coldest. Efficient air flow in your freezer volition likewise contribute to a reduction in the hardening time. Generally, the more meaty the items in your freezer, the less efficient the air catamenia. The size of your batch also affects the cooling time, with larger batches usually taking longer to harden.

1.1.3. STORAGE Weather

Recrystallisation is also dependent on storage conditions, namely temperature and temperature fluctuations (Donhowe & Hartel, 1996), with colder storage temperatures amend for extended shelf life.

i.1.3.1. STORAGE TEMPERATURE

The development of coarseness in ice cream during storage is highly temperature dependent, being particularly rapid at storage temperatures above near -14°C (vi.8°F) (Donhowe & Hartel, 1996; Ben-Yoseph & Hartel, 1998). Earl & Tracy (1960) establish that ice cream stored at -26.one°C (-14.98°F) suffered only slight textural deterioration after sixteen weeks, but storage at -13.3°C (8.06°F) resulted in a fibroid texture afterward simply 2 weeks.

The ideal storage temperature to reduce recrystallisation would be below the drinking glass transition temperature, around -32°C (-25°F), where recrystallisation occurs very slowly (Goff & Sahagian, 1996; Roos, 2010; Goff & Hartel, 2013). Goff & Hartel (2013) note that due south torage below nearly -25°C (-xiii°F) gives a sufficiently slow recrystallisation charge per unit to give extended shelf life.  Donhowe (1993) establish that storage at -20°C (-4°F) resulted in very little increment in hateful ice crystal size, merely, at -5°C (23°F), mean ice crystal size increased from 40 µm to about 220 µm during 5 days of storage.

Labuza and Fu (1998) evidence shelf life information for water ice cream based on sensory iciness perception. In their information, ice foam stored at -10°C (14°F) had a shelf life of nearly 1 week, whereas storage at -20°C (-four°F) and -25°C (-13°F) gave a shelf life of about 10 and 40 weeks respectively.

Ice foam shelf life. From Labuza, T. P., 1982. Open Shelf Life Dating of Foods, Food and Diet Press, West Port, CT.

TIP#2 – LOWER THE STORAGE TEMPERATURE
To reduce recrystallisation during storage and extend shelf life, store your ice cream at around -25°C (-13°F) or lower, ideally effectually -32°C (-25°F).

1.one.three.2. TEMPERATURE FLUCTUATIONS

Recrystallisation during storage is significantly slower for ice cream stored at a constant temperature than for ice cream stored at oscillating temperature conditions (Donhowe & Hartel, 1996). Witting & Smith (1986) showed that water ice creams stored in a 'supermarket-blazon frost/defrost freezer' with temperature cycles between -nine.4°C and -fifteen°C (15.08°F and 5°F) became detectably icy in 4 weeks and objectionably icy in 3-10 weeks.

Temperature fluctuations may be associated with one. changes in the storage temperature equally the ice foam moves from point to point (east.g. from the supermarket to your freezer); 2. rut shocks, where the water ice cream is left at room temperature for extended periods of time and and then re-frozen; 3. temperature fluctuations due to automated defrost cycles; and four. opening and closing of doors in freezers and storage cabinets (Goff & Hartel, 2013).

TIP #three – MINIMISE TEMPERATURE FLUCTUATIONS
To minimise recrystallisation during storage, try to minimise temperature fluctuations by reducing the number of times you take your ice cream out of the freezer, leave it out at room temperature, and so re-freeze it. Also, try to limit the time that your tub of ice cream is left at room temperature by returning it to the freezer as soon equally you've finished scooping. If possible, disable the automobile defrost setting on your freezer and limit the number of times you open and close your freezer door.

1.1.4. COMPOSITIONAL FACTORS

Too freezing and storage conditions, the composition of the water ice cream mix influences recrystallisation. This includes the fat, protein, sweetener, and, stabiliser contents.

1.1.iv.one. MILK Fatty

Milk fat has been shown to influence development of coarseness during storage past providing a mechanical obstruction to ice crystal growth, slowing the rate of recrystallisation (Donhowe & Hartel, 1996; Prindiville et al., 1999). Goff & Hartel (2013) note that the tendency for ice crystals to grow decreases in the following order: nonfat, low-fatty, light, reduced fat, regular, premium, and super premium ice creams.

I've institute a butterfat content of effectually 23% to be optimum in homemade ice cream. Please click here to run into my mix limerick for my vanilla water ice cream recipe.

1.i.4.2. MILK PROTEINS

Milk proteins play a function in reducing rates of water ice recrystallisation, maybe through their water property chapters (Regend & Goff, 2002, 2003).

1.one.4.3. SWEETENERS

Sweeteners affect recrystallisation by depressing the freezing indicate, or lowering the temperature at which the water in an water ice cream mix starts to freeze (Harper & Shoemaker, 1983; Wittinger & Smith, 1986). For an water ice cream mix with a lower freezing point, less water is frozen at a given temperature. Hagiwara & Hartel (1996) found that the lower the freezing point, or the larger the amount of unfrozen water in ice foam, the higher was the recrystallisation rate. Harper & Shoemaker (1983) found similar furnishings of freezing point for the effect of sweeteners on recrystallisation rates. These results suggest that water ice cream formulations with the highest possible freezing signal and the least amount of unfrozen water should have the greatest resistance to recrystallisation.

i.ane.four.iv. STABILISERS

Stabilisers are added to ice cream specifically to control ice recrystallisation (Bahramparvar & Tehrani, 2011). Sutton & Wilcox (1998) showed that both locust bean glue and guar reduced the extent of recrystallisation in water ice foam compared with unstabilised water ice cream. The inhibition of recrystallisation by these stabilisers was concentration dependent upward to a level of about 0.3% after which further add-on did not upshot in further inhibition. Sutton & Wilcox (1998) confirmed findings by Wittinger & Smith (1986) that locust edible bean gum was a better recrystallisation inhibitor than guar. Goff et al. (1993) too found that the ice crystal sizes earlier and after storage were smaller in stabilised ice foam than in ice cream without stabilisers.

1.one.4.5. ICE-STRUCTURING PROTEINS AND PROPYLENE GLYCOL MONOSTEARATE

Water ice-structuring proteins (ISP), found primarily in cold-weather condition-adjusted fish, insects, over-wintering plants, and in bacteria and fungi (Griffith & Ewart, 1995) have been institute to reduce the recrystallisation charge per unit. Regand & Goff (2006) studied ice recrystallisation in frozen sucrose solutions and in water ice foam with or without ice structuring proteins from cold-acclimated winter wheat grass extract (AWWE). Meaning Internet service provider activeness in retarding ice crystal growth was observed in all sucrose solutions containing 0.13% total protein from AWWE. Furthermore, in heat-shocked ice cream, ice recrystallisation rates during storage were significantly reduced with the addition of 0.0025 and 0.0037% total protein from AWWE. A remarkably smoother texture for ice creams containing ISP later heat-stupor was also evident by sensory evaluation.

Propylene glycol monostearate (PGMS), an emulsifier used in cake mixes and aerated toppings, has too been identified as an inhibitor of ice recrystallisation at levels upwardly to 0.v% (Barfod et al, 2005). The addition of 0.three% PGMS was plant to subtract water ice crystal size in ice cream both before and after heat shock (Aleong et al. 2008).

2. LACTOSE CRYSTALLISATION

Lactose crystallisation during storage tin can likewise result in a sandy or coarse texture. Lactose crystals tin be detectable in the mouth when they exceed almost xv µm in size, compared to well-nigh 50 µm for ice crystals (Goff & Hartel, 2013). Lactose crystallisation occurs most readily when ice cream contains milk solids-not-fat (the lactose, proteins, minerals, water-soluble vitamins, enzymes, and some small constituents) levels over nearly 16% and is stored at temperatures from -10°C to -15°C (xiv°F to 5°F) (Livney et al., 1995). Minimising storage fourth dimension and temperature fluctuations, promoting the formation and stabilisation of many small air cells, adding stabilisers, and maintaining depression storage temperatures help minimise lactose crystallisation.

three. AIR Prison cell SIZE

During dynamic freezing, air is incorporated into the mix through the folding and mixing action of the rotating dasher and scraper blades. Conscientious control of the amount of air incorporated into water ice cream, or overrun, and the air cell size distribution is disquisitional for water ice cream texture, meltdown, and hardness (Sofjan & Hartel, 2003; Xinyi et al., 2010), with smaller dispersed air cells producing a creamier mouthfeel during consumption (Eisner et al., 2005).

Similar to ice crystals, mean air bubble size tends to increase over fourth dimension in storage, with a larger rate of growth observed at warmer temperatures (Goff & Hartel, 2013). Pinzer et al. (2012) plant that mean air chimera size increased rapidly at -v°C (23°F) and much more slowly at -15°C (5°F). This change in air bubble size contributes to a change in texture and quality of ice cream by enhancing crumbliness in trunk and significantly increasing the rate of meltdown.

iv. SHRINKAGE

Another problem that occurs during the storage of water ice cream is shrinkage, which appears as the ice cream pulling away from the walls of the container. Shrinkage occurs as the result of air bubbling coalescing (coming together) and forming continuous channels, which then leads to the collapse of the ice foam into these channels (Turan et al. 1999). Contributing factors can be high overrun, depression solids, low protein, and changes in external force per unit area (Dubey & White, 1997). Goff & Hartel (2013) annotation that shrinkage occurs near often afterward ice cream experiences a pregnant decrease in pressure, equally when ice cream is shipped across mountains or transported by plane, which first causes a volume expansion.

Ice cream shrinkage. From Goff & Hartel (2013).

5. SUMMARY

Physicochemical changes in ice foam are generally considered the virtually important in determining shelf life. These  include ice recrystallisation, lactose crystallisation, a change in the size of air cells, and changes in ice foam volume. Water ice recrystallisation (the general increase in water ice crystal size) during storage is considered to take the nigh meaning effect on the shelf life of ice cream because of the adverse effect on texture.

The formation of smaller ice crystals during dynamic freezing, quick hardening to temperatures at or beneath -18°C (0.iv°F) during static freezing, a depression storage temperature of -25°C (-xiii°F) or lower, ideally around -32°C (-25°F), and minimising temperature fluctuations during storage assistance reduce recrystallisation and extend shelf life.

Based on sensory iciness perception, ice cream stored at -10°C (14°F) has a shelf life of about 1 week, whereas storage at -twenty°C (-4°F) and -25°C (-13°F) give a shelf life of about ten and 40 weeks respectively.

I hope this post helps. I'd be happy to answer any questions so do get in touch on and say hi! Ruben 🙂

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