Incorporation of extracellular polysaccharide produced by Xanthomonas campestris into milk powders : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University

The purpose of the research was to investigate the functional properties of milk powders following exopolysaccharide (EPS) addition to milk solutions and their subsequent spray-drying. The aim was to replace some of the milk proteins with polysaccharide in dairy products while maintaining or improving the functional characteristics. Both commercial xanthan EPS and ferment xanthan EPS were incorporated into whole milk powder (WMP), skim milk powder (SMP), and milk protein concentrate (MPC). Ferment EPS was produced from a by-product of the dairy industry, milk permeate, through the hydrolysis of the lactose and fermentation with a strain of Xanthomonas campestris. Ferment EPS had a characteristic and unpleasant odour. The main compound responsible for this odour was p-cresol which, in milk, is largely bound in the conjugate form. Xanthomonas campestris hydrolyses these conjugates releasing the odour compounds. Ultrafiltration (UF) of the ferment or passing the ferment through a bed of activated carbon was effective in reducing the odour. UF was proven to reduce the levels of p-cresol in the ferment from 138ppb to less than 5ppb after 98 concentration factors. Milk powders made with UF ferment were more acceptable to the consumer sensory panel than those made with untreated ferment. The incorporation of EPS into milk powders has beneficial effects on the product with small additions increasing the viscosity of reconstituted SMP and WMP considerably. The EPS addition could result in a thickened milk product or alternatively, substitute for some of the milk solids. Sensory testing showed that 13.3% WMP solution, containing 0.02% commercial EPS, was not detectably different from a 15% WMP solution. The addition of both commercial and ferment EPS into milk powders leads to the formation of separate flocculated casein and polysaccharide phases with reconstituted milk. Confocal microscopy showed that casein flocculation occurred at all EPS concentrations tested, but this only resulted in sedimentation at intermediate EPS concentrations. At high EPS concentrations of approximately 0.2% the high viscosity limited flocculation and prevented sedimentation. At low EPS concentrations of approximately 0.05% flocculation was insufficient to overcome Brownian motion. Fresh cheese (Panela) made from MPC containing either ferment or commercial EPS showed greatly decreased whey loss. This was attributed to (i) the increased viscosity of the continuous phase limiting the flow of liquid through the pores of the cheese, and (ii) diminished casein interaction in the presence of EPS leading to a looser curd and lower contraction forces. For example the incorporation of 0.161% ferment EPS decreased the whey lost by approximately 75%. Negative effects were also apparent. The addition of EPS led to a granular appearance, which became more apparent with increasing EPS concentration. Cheese firmness was also decreased by approximately 40% by the addition of the ferment EPS at 0.161%. This could also be attributed to the localised aggregation of protein during renneting and the increased heterogeneity of the network. Sensory testing of cheeses made with 15.6% MPC + 0.045% commercial EPS compared with cheese made with 17.37% MPC alone showed that the consumers had no significant preference for one cheese over the other, but did notice a difference in texture. For reasons of safety and health, the sensory testing of milk and cheese in this research was confined to commercial xanthan. Future sensory testing of milk and cheese should be conducted with ferment EPS after odour removal rather than commercial EPS, and use consumers familiar with these cheese and milk products. For commercial production of dairy powders containing UF ferment EPS it is vital that either the xanthan or casein micelle structure be altered to prevent casein flocculation. If this is not feasible then an alternative use of the product may need to be found. A potential option involves the addition of the powder containing UF ferment EPS into food products as a minor food constituent. This may limit the occurrence of phase separation while improving the functionality of the product. Commercialisation is also limited by the increasing costs caused by ferment EPS purification and the lower solids concentrations required for spray-drying. As such the viability of the powder production must be determined

Effects of high-pressure processing (HPP) on the microbiological, physicochemical and sensory properties of fresh cheeses : a review

High pressure processing (HPP) is an increasingly popular food processing method that offers great potential within the food industry. The drive to use HPP is to provide minimally processed foods which are safe and have extended shelf-life that rival traditional methods of food processing. HPP is currently being applied to a wide variety of food products, although to date the dairy industry has received little attention. The present paper reviews the effects of HPP on fresh rennet- and acid-coagulated cheeses. In additional to modifying physicochemical and sensory characteristics, HPP is reported to inactivate certain micro-organisms typically found in cheeses. Pathogenic microorganisms such as Listeria monocytogenes and Escherichia coli which contaminate, spoil and limit the shelf-life of cheese can be controlled by HPP. HPP can also cause changes in milk rennet coagulation properties, produce a more continuous or homogeneous protein matrix in cheese, improve cheese structure, texture and yield, as well as reduce moisture content variations within fresh cheese blocks. Providing HPP can be operated economically, the use of pressure may be an attractive new method for the processing of cheese

Consumption of a high-fat meal containing cheese compared with a vegan alternative lowers postprandial C-reactive protein in overweight and obese individuals with metabolic abnormalities: a randomised controlled cross-over study.

Dietary recommendations suggest decreased consumption of SFA to minimise CVD risk; however, not all foods rich in SFA are equivalent. To evaluate the effects of SFA in a dairy food matrix, as Cheddar cheese, v. SFA from a vegan-alternative test meal on postprandial inflammatory markers, a randomised controlled cross-over trial was conducted in twenty overweight or obese adults with metabolic abnormalities. Individuals consumed two isoenergetic high-fat mixed meals separated by a 1- to 2-week washout period. Serum was collected at baseline, and at 1, 3 and 6 h postprandially and analysed for inflammatory markers (IL-6, IL-8, IL-10, IL-17, IL-18, TNFα, monocyte chemotactic protein-1 (MCP-1)), acute-phase proteins C-reactive protein (CRP) and serum amyloid-A (SAA), cellular adhesion molecules and blood lipids, glucose and insulin. Following both high-fat test meals, postprandial TAG concentrations rose steadily (P < 0·05) without a decrease by 6 h. The incremental AUC (iAUC) for CRP was significantly lower (P < 0·05) in response to the cheese compared with the vegan-alternative test meal. A treatment effect was not observed for any other inflammatory markers; however, for both test meals, multiple markers significantly changed from baseline over the 6 h postprandial period (IL-6, IL-8, IL-18, TNFα, MCP-1, SAA). Saturated fat in the form of a cheese matrix reduced the iAUC for CRP compared with a vegan-alternative test meal during the postprandial 6 h period. The study is registered at clinicaltrials.gov under NCT01803633

Microbiological and chemical profiles of dairy farm red smear cheese made from pasteurized and un-pasteurized milk

A red-smear soft cheese was produced four times during a year at an organic dairy farm using pasteurized and un-pasteurized milk, respectively, from the same milking. A commercial starter culture was added. The cheeses were characterized microbiologically and chemically in order to study how heat treatment and season affected their characteristics during cheese making and ripening. Large variations between the different lots of cheeses characterized the production. However, the cheeses made from un-pasteurized milk generally had a higher lactic acid bacteria count except in cases, where the pasteurized milk was recontaminated or if acidification failure took place. Delays in acidification caused a more pronounced increase in numbers of E.coli, Enterobacteriaceae and staphylococci, as well as an increase in the plasmin and plasminogen-derived activities. A number of pre-milking and process steps were identified as important for the microbiological contamination and development in the cheeses

U.S. Imports of Concentrated Milk Proteins: What We Know and Don't Know?

International Relations/Trade, Livestock Production/Industries,

Product Quality in the Canadian Dairy Industry

Supply management has been shown to increase the price of milk. Technological change has induced (and allowed) processors to substitute alternative inputs, many of which can be imported tariff-free, for the traditional ingredients to lower costs and maximize profit. Meanwhile, there has been a great deal of consolidation in the dairy processing industry. We analyse the effect of these trends on cheese quality by measuring the increase in casein imports. Results suggest that supply management is negatively affecting cheese quality, by increasing casein imports due to the higher milk price. Furthermore, we were able to calculate that approximately 9.8% of specialty cheese is produced used casein. A 22% ad valorem tariff is needed to drive casein imports down to zero.Food Consumption/Nutrition/Food Safety, Industrial Organization,

Agricultural policy (AP2011) Reform and the WTO: Potential Impacts on Swiss Agriculture

This article analyses the impact of the planned Swiss package of agricultural policy measures AP2011 and the tariff reductions scheduled as part of the WTO Doha Round, with special emphasis on effects in the dairy and meat sector. The simulations are carried out using an extended partial equilibrium model. This article discusses the anticipated impact of changing structural conditions on production, processing, consumption, prices and exports in the milk market. If account is taken of the Bilateral Agreements between Switzerland and the EU providing for liberalisation of the common cheese market, raw milk production increases by 10.5 %, whereas the milk price shows a significant drop to around 60 centimes per kilogram of milk. The abolition of subsidies will result in comparatively more milk being processed into high value-added products. All WTO scenarios have a negative impact on the dairy and meat market. The results reveal that Pork meat is sensitive to the tariff reduction formula under the WTO draft proposal.Partial equilibrium model, simulation, AP2011, WTO, dairy industry, Agricultural and Food Policy, International Relations/Trade, Livestock Production/Industries,

The Prevalence and Control of Bacillus and Related Spore-Forming Bacteria in the Dairy Industry

peer-reviewedMilk produced in udder cells is sterile but due to its high nutrient content, it can be a good growth substrate for contaminating bacteria. The quality of milk is monitored via somatic cell counts and total bacterial counts, with prescribed regulatory limits to ensure quality and safety. Bacterial contaminants can cause disease, or spoilage of milk and its secondary products. Aerobic spore-forming bacteria, such as those from the genera Sporosarcina, Paenisporosarcina, Brevibacillus, Paenibacillus, Geobacillus and Bacillus, are a particular concern in this regard as they are able to survive industrial pasteurization and form biofilms within pipes and stainless steel equipment. These single or multiple-species biofilms become a reservoir of spoilage microorganisms and a cycle of contamination can be initiated. Indeed, previous studies have highlighted that these microorganisms are highly prevalent in dead ends, corners, cracks, crevices, gaskets, valves and the joints of stainless steel equipment used in the dairy manufacturing plants. Hence, adequate monitoring and control measures are essential to prevent spoilage and ensure consumer safety. Common controlling approaches include specific cleaning-in-place processes, chemical and biological biocides and other novel methods. In this review, we highlight the problems caused by these microorganisms, and discuss issues relating to their prevalence, monitoring thereof and control with respect to the dairy industry.NG is funded by the Teagasc Walsh Fellowship Scheme and through the Irish Dairy Levy funded project ‘Thermodur-Out.

PRODUCT QUALITY IN THE CANADIAN DAIRY INDUSTRY

Supply management has been shown to increase the price of milk. Technological change has induced (and allowed) processors to substitute alternative inputs, many of which can be imported tariff-free, for the traditional ingredients to lower costs and maximize profit. Meanwhile, there has been a great deal of consolidation in the dairy processing industry. We analyse the effect of these trends on cheese quality by measuring the increase in casein imports. Results suggest that supply management is negatively affecting cheese quality, by increasing casein imports due to the higher milk price. Furthermore, we were able to calculate that approximately 9.8% of specialty cheese is produced used casein. A 22% ad valorem tariff is needed to drive casein imports down to zero.Industrial Organization,