High pressure processing for better ice cream

Milk proteins play a crucial role in many food products, including ice cream. In this aerated frozen emulsion, milk proteins are crucial in the emulsification of the fat, the stabilization of air bubbles and the structuring of the continuous phase throughout which air bubbles and ice crystals are dispersed. When ice cream mixes are subjected to treatment by high pressure processing (HPP) prior to freezing, the casein micelles in milk are disrupted. As a result, the viscosity of the ice cream mix is increased strongly and ice cream free of stabilizer can be produced, without compromising on the stability and mouth feel of the product. Structuring of milk proteins in ice cream by HPP or other means thus offers opportunities for the replacement of fat and stabilizers in ice cream without compromising on hedonic quality parameters. ICE CREAM STRUCTURE Another widely-popular product in which milk proteins play a crucial role is ice cream. To produce ice cream, a mix is first prepared which contains fat, milk solids non-fat (MSNF), sweeteners, emulsifiers and stabilizer. Initial processing of this mix typically involves formulation, homogenization and pasteurization, following which it is aged for at least four hours at 4°C or lower; this step induces sufficient crystallization of the fat and restructuring of the emulsion droplet surface to facilitate sufficient partial coalescence of the fat droplets during freezing. The aged mix is then simultaneously aerated and frozen, typically using a continuous scraped-surface ice cream freezer. A schematic outline of the resulting ice cream structure is shown in Figure 2; ice cream has a continuous serum phase, with prominent ice crystals and air bubbles, stabilized by a network of partially-coalesced fat globules, in the matrix (1). In ice cream, the milk proteins contribute three crucial functional properties to development and maintenance of the desirable structure of ice cream (1): 1. Emulsification. In ice cream, milk proteins contribute strongly to emulsification of the fat and to partial coalescence of the fat globules and fat structure formation during ice cream manufacture. It is critical that the emulsion droplets are stable during mix preparation, but yet susceptible to partial coalescence during the freezing stage in manufacture. This can happen because the fat droplets are primarily covered by milk protein immediately after emulsification, but are gradually displaced by low molecular mass emulsifiers (e.g., monoglycerides) during ripening of the ice cream mix. 2. Aeration. Milk proteins play a crucial role in the stabilization of air bubbles during the initial stages of ice cream manufacture. During the manufacture of ice cream, a i r i s incorporated in ice cream to approximately 50 percent of the volume phase of the final product. To stabilize this expanding air-liquid interface, it needs to be rapidly covered by surface active compounds. In ice cream, milk proteins dominate the air-water interface. 3. Structuring. In addition to emulsification and aeration, milk proteins play a crucial role in structuring the serum phase of ice cream. The hydration of milk proteins is important for the rheological properties of the serum phase of the ice cream. Together with the stabilizers, the INTRODUCTION Due to their abundance, ease of isolation and crucial role in human nutrition, milk proteins are the best characterized and most widely used food proteins. Milk proteins distinguish themselves from most other food proteins in that they naturally exist in an aqueous environment and are thus readily soluble. This solubility is combined with a high nutritional value, bland flavour profile and wide array of desirable functional properties, such as emulsification, foaming, gelation and heat stability. Two classes of milk proteins exist, i.e., the caseins and the whey proteins, which represent ~75 percent and 25 percent of protein in bovine milk, respectively. The whey proteins are a diverse class of globular, heat-labile proteins, of which α-lactalbumin, β-lactoglobulin, serum albumin and the immunoglobulins are the most abundant, whereas the caseins are a class of 4 rather unique phosphoproteins that exist in milk in the form of stericallystabilized association colloids called casein micelles. These casein micelles are highly hydrated, containing ~75 percent water, and consist of ~10000 casein molecules, as well as small quantities of calcium phosphate. Casein micelles typically have a diameter of ~200 nm (Figure 1). The unique properties of caseins and whey proteins, their interactions during processing (e.g., heat treatment), and their interaction with salts, are responsible for the desirable properties of a wide array of popular dairy and non-dairy food products, including cheese, yoghurt, caramels and milk shakes. Thom Huppertz High pressure processing for better ice cream THOM HUPPERTZ1*, MARY A. SMIDDY2, ALAN L. KELLY2, H. DOUGLAS GOFF3 *Corresponding author 1. NIZO food research P.O. Box 20 Ede, 6710BA, The Netherlands 2. University College Cork Department of Food and Nutritional Sciences Cork, Ireland 3. University of Guelph Department of Food Science Guelph, Canada Figure 1. Scanning electron micrograph (left) and schematic outline (right) of a casein micelle, showing caseins in red, calcium phosphate nanoclusters in black and the solvent phase in white. Fod tecologies building, emulsification and foaming. Improvement of the textural properties of food products is a continuously increasing trend, which has long focussed on the creation of low-fat products. More recent trends also drive innovations towards low-salt and low-calorie food products. In addition, particularly for the elderly, there is currently a great demand for high-protein products. All these trends create increasing challenges for the food industry, to meet nutritional demands without compromising flavour, texture and stability of the products. While polysaccharide-based stabilizers have traditionally been applied widely as a convenient solution for texture improvement, such applications have also come under increasing pressure, due to consumer demands for additive-free, clean-label, food products. With these demands for tasty and nutritious clean-label food products, protein functionality has now, more than ever, become paramount for the food industry in achieving its goals. Innovative processing technologies, such as treatment with high pressure processing (HPP), ultrasound and pulsed electric fields, and biochemical modifications, such as enzymatic cross-linking and deamidation or glycation, are of interest as novel strategies for improving food texture. Some particularly promising results in this respect have been reported for HPP for structuring proteins in ice cream application. HPP involves the batch-wise or semi-continuous treatment of products at pressures ranging from ~100-600 MPa (1000-6000 bar). Commonly, samples are placed in a vessel which is subsequently closed, and pressure is built up using water, or another fluid, as a pressure-transmitting medium. Once the desired pressure is reached, the sample is maintained at this pressure for a certain time, after which pressure is released (2). Industrially, vessels with volumes of several hundred litres are available. milk proteins are the primary determinants of the serum phase viscosity, and hence control the growth and stability of ice crystals. IMPROVING PROTEIN FUNCTIONALITY Despite the high functionality of milk proteins, consumer trends towards nutritious and healthy clean-label food products have put additional demands on milk proteins to deliver functional properties such as gelation, viscosity Figure 2. Schematic outline of ice cream structure. RANDOX FOOD DIAGNOSTICS – PROVIDING RELIABLE FOOD SAFETY SCREENING Randox Food Diagnostics is an associate of Randox Laboratories who have 30 years experience in the diagnostic market and a dedicated research and development team. Randox Food Diagnostics are responsible for the distribution of Randox drug residue kits, wine testing kits and analysers worldwide. In order to meet legislative food safety requirements laboratories need rapid and sensitive screening methods for the detection of these drug residues. Randox offers a versatile range of kits that include an extensive list of drug residue ELISA and multi-analyte biochip products providing a range of excellent screening platforms for detection of antimicrobials, growth promoting hormones, drugs of abuse, anthelmintics and betalactams in animals and foodstuffs. The biochip testing platform uses the world’s only multi-analyte quantitative Drug Residue analyser; the Evidence Investigator. This multiplex platform provides simultaneous detection of an extensive list of compounds using sample matrices including muscle, liver/kidney, seafood, milk, honey, urine and animal feed. This multiplex testing format reduces cost, run time and labour requirements and guarantees faster turnaround time for results and a higher throughput (675 tests in under 2 hours). Randox Food Diagnostics offers cost effective screening solutions using patented biochip technology. For more information visit www.randoxfooddiagnostics.com or contact: enquiries@randoxfooddiagnostics.com A dynamic space for dynamic innovation. Companies introduce on a nearly daily basis novel innovative solutions! Fast and reliable communication becomes a must. “The Corner” is a dedicated fast track space allowing companies to showcase their most advanced products to the specialized readership in nearly real time. Each issue of Agro FOOD hi-tech hosts a dedicated Corner dealing with the hottest topics of the moment. This corner in particular focuses on Analytical Technologies.