erties, placing themselves in the interfacial layer between the fat/ protein and water and helping to improve or control: • Fat emulsification in the mix • Fat agglomeration and coalescence • Air incorporation • Dryness on extrusion • Melting resistance • Heat-shock stability • Smoothness and creaminess The most common emulsifiers used in ice cream are mono-diglycerides (E471), lactic acid esters (E472b), propylene glycol esters (E477) and blends of these. Generally speaking, good compositions can be made with most of the widely-used emulsifiers and stabilizers such as mono- and diglycerides, carrageenan and locust bean gum. If, that is, they are used in the right amount and compositions to suit each recipe. Adding propylene glycol esters such as propylene glycol monostearate (PGMS), for example, protects against the Heat Shock Effect by ensuring small ice crystals are created during freezing and reducing their tendency to grow during the journey to the consumer’s table, as shown in Figure 3. Process considerations During the freezing stage of ice cream production, the goal is to create as many small ice crystals as possible, providing as large a total surface area as possible. Figure adapted from: Ice Recrystallization Inhibition in Ice Cream by Propylene Glycol Monostearate, Aleong, J. M. Frochot, S. and Goff, H. D. JFS 73, 9, 2008 Figure 3 shows how propylene glycol esters (PGMS) emulsifiers maintain ice crystal size despite fluctuating transport and storage temperatures. Unfortunately, control is not always strict enough in this stage of production, with some plants transporting the ice cream via long pipes where the temperature may raise, for example, to -3 °C (26.6 °F) before filling begins. The filling process elevates the temperature further, then there is likely to be waiting time on a pallet, too, until the pallet is full and can be placed in appropriately cold storage. In warm climates or seasons, this can have quite an effect, with some of the ice crystals already starting to melt, turning into water and becoming part of the growth of other crystals. The longer it takes to deep-freeze the entire product, the more water will move in this way and the greater early heat shock damage will be. Attention also needs to be paid to aging, the stage that takes place between mixing and freezing steps, requiring pasteurization to dissolve the emulsifiers and stabilizers and kill off bacteria, as well as homogenization to support the fat structure, and cooling at -5 °C (23 °F) for anything from 4 hours to overnight. Integrated emulsifiers and stabilizers Figure 4 depicts two melting curves of an ice cream that was melted using a special machine for accurate measurement. The amount of ice cream landing in bowls placed under the product was measured as a percentage of its overall weight. The upper curve reflects an ordinary ice cream recipe, while The freezer process, which also includes whipping, doesn’t freeze all the water, as the ice cream leaves the freezer at around -6 °C (21.2 °F) ready for filling in tubs or placing onto sticks. As soon as this is done, and to provide the best starting point for heat shock protection, the product needs to be placed as quickly as possible into a hardening tunnel at -40°C (-40 °F) and then finally in the storage freezer at -18°C (-0.4°F). Figure 4: Melting curves of ice cream produced with and with out emulsifiers and stabilizers. Ice cream without emulsifier/stabilizer % Ice cream with Palsgaard® ExtruIce emulsifier/stabilizer 100 90 80 70 60 50 40 30 20 10 0 Time (min) 0.0 3.4 7.2 11.0 14.4 18.2 22.0 25.4 29.2 33.0 38.4 40.2 44.0 47.4 51.2 55.0 58.4 62.2 68.0 69.4 73.2 77.0 80.4 84.2 88.0 3
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