Properties of frozen dairy desserts processed by microfluidization of their mixes

Sensory properties and rate of meltdown of nonfat (0% fat) and low-fat (2% fat) vanilla ice creams processed either by conventional valve homogenization or microfluidization of their mixes were compared with each other and to ice cream (10% fat) processed by conventional valve homogenization. Mixes for frozen dairy desserts containing 0, 2, and 10% fat were manufactured. Some of the nonfat and low-fat ice cream mixes were processed by microfluidization at 50, 100, 150, and 200 MPa, and the remaining nonfat and low-fat ice cream mixes and all of the ice cream mix were processed by conventional valve homogenization at 13.8 MPa, first stage, and 3.4 MPa, second stage. The finished frozen and hardened products were evaluated at d 1 and 45 for meltdown rate and for flavor and body and texture by preference testing. Nonfat and low-fat ice creams that usually had a slower meltdown were produced when processing their mixes by microfluidization instead of by conventional valve homogenization. Sensory scores for the ice cream were significantly higher than sensory scores for the nonfat and low-fat ice creams, but the sensory scores for the conventional valve homogenized controls for the nonfat ice cream and low-fat ice cream were not significantly different from the sensory scores for the nonfat ice cream and low-fat ice cream processed by microfluidization of the mixes, respectively. Microfluidization produced nonfat and low-fat ice creams that usually had a slower meltdown without affecting sensory properties.     

A 100-Year Review: Milestones in the development of frozen desserts

Ice cream has come a long way since the first snow cone was made. Innovations in a variety of areas over the past century have led to the development of highly sophisticated, automated manufacturing plants that churn out pint after pint of ice cream. Significant advances in fields such as mechanical refrigeration, chilling and freezing technologies, cleaning and sanitation, packaging, and ingredient functionality have shaped the industry. Advances in our understanding of the science of ice cream, particularly related to understanding the complex structures that need to be controlled to create a desirable product, have also enhanced product quality and shelf stability. Although significant advances have been made, there remain numerous opportunities for further advancement both scientifically and technologically.     

Major advances in concentrated and dry milk products, cheese, and milk fat-based spreads

Advances in dairy foods and dairy foods processing since 1981 have influenced consumers and processors of dairy products. Consumer benefits include dairy products with enhanced nutrition and product functionality for specific applications. Processors convert raw milk to finished product with improved efficiencies and have developed processing technologies to improve traditional products and to introduce new products for expanding the dairy foods market. Membrane processing evolved from a laboratory technique to a major industrial process for milk and whey processing. Ultra-filtration and reverse osmosis have been used extensively in fractionation of milk and whey components. Advances in cheese manufacturing methods have included mechanization of the making process. Membrane processing has allowed uniform composition of the cheese milk and starter cultures have become more predictable. Cheese vats have become larger and enclosed as well as computer controlled. Researchers have learned to control many of the functional properties of cheese by understanding the role of fat and calcium distribution, as bound or unbound, in the cheese matrix. Processed cheese (cheese, foods, spreads, and products) maintain their importance in the industry as many product types can be produced to meet market needs and provide stable products for an extended shelf life. Cheese delivers concentrated nutrients of milk and bio-active peptides to consumers. The technologies for the production of concentrated and dried milk and whey products have not changed greatly in the last 25 yr. The size and efficiencies of the equipment have increased. Use of reverse osmosis in place of vacuum condensing has been proposed. Modifying the fatty acid composition of milkfat to alter the nutritional and functional properties of dairy spread has been a focus of research in the last 2 decades. Conjugated linoleic acid, which can be increased in milkfat by alteration of the cow's diet, has been reported to have anticancer, anti-atherogenic, antidiabetic, and antiobesity effects for human health. Separating milk fat into fractions has been accomplished to provide specific fractions to improve butter spreadability, modulate chocolate meltability, and provide texture for low-fat cheeses.     

冰淇淋中奶粉替代品的研究

从考察产品的感官指标和理化性能入手,采用玉米淀粉、大豆蛋白、糊精、变性淀粉等原料替代奶粉,对冰淇淋生产的配方进行了试验,筛选出了用植物性原料替代奶粉生产冰淇淋的最佳配方。     

豆奶冰淇淋的工艺研究

用豆奶和牛奶结合制作冰淇淋,关键是去除豆腥味。本文从浸豆、磨浆、配方选择等方面进行了探讨。     

The microstructural,melting, rheological,and sensorial properties of high-overrun frozen desserts

Air incorporated during dynamic freezing influences the development of the microstructure and the final texture of frozen desserts. Frozen desserts were manufactured with 100–175% overrun from a constant ice cream mix formulation. Microstructural elements (fat, air, and ice phases) of the frozen desserts were then investigated and related to the melting, rheological, and sensory properties of the product. Mean ice crystal and air cell size were found to decrease with increasing overrun, and the extent of fat destabilization increased. Frozen desserts manufactured with higher overrun had slower drip-through rate and better shape retention after melting at ambient conditions, demonstrating that fat destabilization and the interplay of fat, air, and serum phases affect the melting behavior. Structural elements also influenced the rheological behavior, as measured by oscillatory thermo-rheometry. Frozen desserts had similar rheological properties at temperatures below the freezing point due to the presence of ice, and the values of G′ and G″ (solid-like and viscous-like character, respectively) increased with increasing overrun above the freezing point, corresponding to a more solid-like structure. Slight differences in sensory denseness and breakdown were detected, but sensory texture was not significantly different for the frozen desserts studied. This study provided insights into the role of air in ice cream and frozen desserts, and its influence on product texture.     

Major advances in nutrition: impact on milk composition

A number of major scientific advances have been realized in the last 25 yr in determining the opportunities and limitations of altering milk composition through nutritional manipulation. Because of the greater sensitivity of milk fat to dietary manipulation than either protein or lactose, nutritional control of milk fat content and fatty acid composition received a great deal of attention. New information emerged linking ruminal production of trans fatty acid isomers with milk fat depression. As a result, research on fatty acid biohydrogenation intensified yielding new insight on the origin of specific trans fatty acid isomers originating from ruminal biohydrogenation and how these isomers were modified by the action of mammary enzymes. The discovery of conjugated linoleic acid (CLA) as a potent anticarcinogen also led to extensive work on enhancing its concentration in milk through nutritional manipulation and discovering the physiological effects of specific CLA isomers. New protected fats were developed in recent years that were designed to resist biohydrogenation and enhance the concentration of unsaturated fatty acids in milk. The nutritional factors receiving the most attention during the last 25 yr for their influence on milk protein content were forage-to-concentrate ratio, the amount and source of dietary protein, and the amount and source of dietary fat. New insights were tested on modes of action whereby fat supplements caused a decline in protein concentration. Changes in milk lactose concentration occur only in extreme and unusual feeding situations, but the basic biology of lactose synthesis and regulation are still being explored using modern molecular techniques. This paper highlights the major advances in controlling milk composition by dietary manipulation and how it influences the entire animal system from practical feeding studies to basic cellular work on mammary tissue metabolism.     

乳清产品在冰淇淋和冷冻乳制品甜食中的应用

<正> 乳清和乳清蛋白产品在过去的60多年中已经被成功应用于冰淇淋和其他冷冻乳制品甜食中。甜乳清、乳清浓缩蛋白(蛋白质含量34～89%)和乳清分离蛋白(蛋白质含量≥90%)是最常用的乳清产品。其他的乳清配料,如脱乳糖乳清和脱盐乳清也是常用的配料。成本优势和提升产品质量是使用乳清产品的主要出发点,     

Physical properties of ice cream containing milk protein concentrates

Two milk protein concentrates (MPC, 56 and 85%) were studied as substitutes for 20 and 50% of the protein content in ice cream mix. The basic mix formula had 12% fat, 11% nonfat milk solids, 15% sweetener, and 0.3% stabilizer/emulsifier blend. Protein levels remained constant, and total solids were compensated for in MPC mixes by the addition of polydextrose. Physical properties investigated included apparent viscosity, fat globule size, melting rate, shape retention, and freezing behavior using differential scanning calorimetry. Milk protein concentrate formulations had higher mix viscosity, larger amount of fat destabilization, narrower ice melting curves, and greater shape retention compared with the control. Milk protein concentrates did not offer significant modifications of ice cream physical properties on a constant protein basis when substituted for up to 50% of the protein supplied by nonfat dry milk. Milk protein concentrates may offer ice cream manufacturers an alternative source of milk solids non-fat, especially in mixes reduced in lactose or fat, where higher milk solids nonfat are needed to compensate other losses of total solids.     

Major advances associated with the biosynthesis of milk

The mammary gland has an incredible level of organization and a remarkable ability to convert circulating nutrients into milk components. This review highlights four areas of high interest in the biology of milk synthesis where advances over the last quarter-century have resulted in new understanding or revealed new opportunities. First, advances in our understanding of the mechanisms of milk secretion has led to a substantial increase in our knowledge of the intracellular origin of lipid droplets and the identity and potential function of milk fat globule membrane proteins in milk-lipid secretion. Second, recent breakthroughs have advanced our understanding of the nutritional regulation of milk fat and highlighted the interrelations between dietary components, digestive processes in the rumen, and the regulation of mammary synthesis of milk fat. Third, nutritional quality is becoming increasingly important in food choices because of consumer awareness of the links between diet and health. The traditional nutritional value of milk and dairy products is well established, but recent discoveries have identified a number of “bioactive” components in milk with potential to improve human health. Finally, the concept of genetic engineering and the use of animals as “bioreactors” and the “pharming” of proteins not normally found in milk have gained recognition, with the dairy industry ideally suited to take advantage of advances in these areas.     

Major advances in milk marketing: government and industry consolidation

Federal dairy programs have been instituted to assist dairy farmers in marketing their milk. Milk marketing licenses were issued for city markets in 1933 during the depression. Federal Milk Orders replaced licenses in 1937 with enactment of the Agricultural Marketing Agreement Act. Low prices returned in the late 1940s and Congress passed the Agricultural Act of 1949 creating the support program for milk. Congressional involvement in milk marketing was minimal until passage of the 1977 Farm Bill. A support price adjustment to seek favorable political responses from farmers resulted in higher prices and ultimately higher production. Large expenditures and burdensome supplies caused Congress to make major changes to both programs. Other milk marketing programs have evolved from Congressional actions, including export and promotion programs. The exiting and consolidation of the dairy processors and producers has lead to a reduction in the number of marketing orders.     

开菲尔酸豆乳冰淇淋的研制

以豆乳代替部分牛乳并用开菲尔进行发酵,研制出开菲尔酸豆乳冰淇淋。选择煮浆时间、豆粉奶粉比例、白砂糖添加量、复合乳化稳定剂添加量、老化时间和凝冻档位作为单因素进行梯度实验,对发酵时间、接种量和发酵温度进行三因素三水平L9（33）正交实验,确定开菲尔酸豆乳冰淇淋的最佳工艺为:取浸泡好的大豆,与水按照1∶11的比例进行磨浆,过滤,沸腾后煮浆5 min,制得豆乳;以豆浆重量为基准,加入8%豆粉、5%奶粉、16%白砂糖和0.65%复合乳化稳定剂,倒入制浆机中搅拌并杀菌,待均质后的料液冷却到38℃加入料液总质量0.2%的开菲尔发酵剂,38℃发酵8 h,得到发酵乳;将发酵乳置于4℃老化缸中老化4 h,然后将料液倒入冰淇淋机器设置成三档（凝冻温度-7℃）,制得开菲尔酸豆乳冰淇淋。      

A decade of improvement: New York State fluid milk quality

The microbiological and sensory qualities of New York State (NYS) fluid milk products were assessed as part of an ongoing fluid milk quality program. Commercially packaged pasteurized fluid milk samples were collected twice a year over the 10-yr period from 2001 to 2010 from 14 NYS dairy processing facilities and analyzed at the Milk Quality Improvement Program (MQIP) laboratory. Each sample was tested throughout refrigerated storage (6°C) on day initial, 7, 10, and 14 for standard plate count (SPC), coliform count (CC), and sensory quality. Over the 10-yr period, the percentage of samples with bacterial numbers below the Pasteurized Milk Ordinance (PMO) limit of 20,000 cfu/mL at d 14 postprocessing ranged from a low of 21.1% in 2002 to a high of 48.6% in 2010. Percent samples positive for coliforms during that same period ranged from a high of 26.6% in 2002 to a low of 7.5% in 2007. Mean d 14 sensory scores ranged from a low of 6.0 in 2002 to a high of 7.3 in 2007. Samples contaminated with coliforms after pasteurization have significantly higher SPC counts and significantly lower sensory scores on d 14 of shelf-life than those not contaminated with coliforms. Product factors such as fat level were not significantly associated with SPC, CC, or sensory quality of the product, whereas the factor processing plant significantly affected overall product quality. This study demonstrates that overall fluid milk quality in NYS, as determined by microbiological and sensory analyses, has improved over the last decade, and identifies some challenges that remain.     

Physical properties of supercritical fluid extrusion products composed of milk protein concentrate with carbohydrates

Supercritical fluid extrusion (SCFX) is a novel process combining traditional extrusion and supercritical fluid technologies. The objective of this study was (i) to assess the effect of sugar, maltodextrin and cornstarch on the physical properties of milk protein concentrate (MPC) puffed extrudates and (ii) to compare the physical and textural properties of SCFX puffed MPC products with commercially puffed cereal products. Results showed that the nutritious MPC puffed products with carbohydrates can be made with textural properties (hardness, brittleness and crispness) resembling those of the commercial samples. The porosity of F2 (0.573) was assessed to the commercial product C1 (0.543) and C2 (0.595), the specific length of F3 (50.41) was assessed to C1 (45.51) and F4 (80.14) was assessed to C2 (78.12). The hardness of extrudate F3 (435.49 KPa) was assessed to C2 (482.7 KPa). The Young's modulus of F5 (87.03) was assessed to C2 (80.57). The starches affected the crispness of the extrudates, and sugar affected the hardness and brittleness significantly.     

Nutrient content of milk and milk products: Vitamins of the B complex and vitamin C in retail creams,ice creams and milk shakes

A study was undertaken to update and extend information on the water-soluble vitamin content of creams, ice creams and take-away milk shakes on retail sale in the UK. The concentration of water-soluble vitamins in creams reflected to varying extents the level of fat and the type of heat processing. The concentration of vitamins in both dairy and non-dairy ice creams were generally similar. The amounts of vitamins in milk shakes were similar to those in pasteurised milk.     

Effect of biopolymers on structure and ice recrystallization in dynamically frozen ice cream model systems

Ice crystal growth and microstructure of sugarsolutions prepared with stabilizers (carboxymethyl cellulose [CMC], xanthan gum, locust bean gum [LBG], and gelatin) with or without milk solids-nonfat (MSNF) after freezing in a scraped surface heat exchanger and temperature cycling (5 cycles from -6 degrees C to -20 degrees C) were studied. Ice crystal growth was calculated from brightfield microscopic images acquired from samples before and after cycling. Freeze-substitution and low-temperature embedding (LR-Gold resin) were sample preparation techniques utilized for structure analyses by light microscopy and transmission electron microscopy. Differential staining for carbohydrates and proteins allowed the identification of stabilizer gel-like structures in LBG, gelatin, and gelatin/MSNF solutions. In the absence of milk proteins, xanthan and LBG were the most effective at retarding recrystallization, while in their presence, only xanthan had an effect. Cryo-gelation of the LBG was observed but is not the only mechanism of stabilizer action. Thermodynamic incompatibility between biopolymers was observed to promote localized high concentrations of milk proteins located at the ice crystal interface, probably exerting a water-holding action that significantly enhanced the stabilizer effect. Qualitatively, solution heterogeneity (phase separation) was directly proportional to ice crystal growth inhibition. It is suggested that water-holding by stabilizer and proteins, and in some cases steric hindrance induced by a stabilizer gel-like network, caused a reduction in the kinetics of the ice recrystallization phenomena and promoted mechanisms of melt-regrow instead of melt-diffuse-grow recrystallization, thus resulting in the preservation of the ice crystal size and in a small span of the ice crystal size distribution.     

Forecasting fluid milk and cheese demands for the next decade

Predictions of future market demands and farm prices for dairy products are important determinants in developing marketing strategies and farm-production planning decisions. The objective of this report was to use current aggregate forecast data, combined with existing econometric models of demand and supply, to forecast retail demands for fluid milk and cheese and the supply and price of farm milk over the next decade. In doing so, we can investigate whether projections of population and consumer food-spending patterns will extend or alter current consumption trends and examine the implications of future generic advertising strategies for dairy products. To conduct the forecast simulations and appropriately allocate the farm milk supply to various uses, we used a partial equilibrium model of the US domestic dairy sector that segmented the industry into retail, wholesale, and farm markets. Model simulation results indicated that declines in retail per capita demand would persist but at a reduced rate from years past and that retail per capita demand for cheese would continue to grow and strengthen over the next decade. These predictions rely on expected changes in the size of populations of various ages, races, and ethnicities and on existing patterns of spending on food at home and away from home. The combined effect of these forecasted changes in demand levels was reflected in annualized growth in the total farm-milk supply that was similar to growth realized during the past few years. Although we expect nominal farm milk prices to increase over the next decade, we expect real prices (relative to assumed growth in feed costs) to remain relatively stable and show no increase until the end of the forecast period. Supplemental industry model simulations also suggested that net losses in producer revenues would result if only nominal levels of generic advertising spending were maintained in forthcoming years. In fact, if real generic advertising expenditures are increased relative to 2005 levels, returns to the investment in generic advertising can be improved. Specifically, each additional real dollar invested in generic advertising for fluid milk and cheese products over the forecast period would result in an additional $5.61 in producer revenues.