Within the dairy chain, processing of milk plays an extremely important role. First and foremost, it is required to improve the safety and extent the shelf-life of products, thereby ensuring that products can be safely distributed all over the world. This shelf-life extension can be achieved through heat treatment, but also through fermentation or drying. In addition, processing is also important to ensure that a dairy matrix is created which is preferable by consumers, which can be digested and from which nutrients bioavailable. Such processing can include similar steps as for shelf-life extension, but also other processing techniques, including e.g., non-thermal processing.
Alan Kelly (University College Cork, Ireland)
University of Copenhagen, Denmark
1Wageningen University and Research, The Netherlands
In aerated dairy emulsions like whipped cream and ice cream, the characteristic sensorial and rheological properties are largely dependent on the formation of a three-dimensional fat globule network. This network is formed when fat globules undergo partial coalescence (also called arrested coalescence) meaning they are able to begin merging but do not fully combine into one spherical globule. Although the existence of partially-coalesced fat globule networks is well documented, the underlying mechanism of when and how partial coalescence occurs is not. For this reason, the coalescence behavior of fat globule pairs was studied using a technique called micromanipulation. By using two capillary tubes to manually put two fat globules into contact, the entire coalescence event could be observed. By utilizing micromanipulation, several studies have been undertaken to further understand how solid fat content, fat composition, emulsifier concentration, emulsifier type, and droplet size impact the extent of coalescence between fat globules. The overall goal is to map out regions where partial coalescence will occur to ensure the stability and high quality of aerated dairy emulsions.
Controlling partial coalescence in aerated dairy emulsions influences the stand-up, meltdown, and other rheological behaviors of the final product. The extent of partial coalescence can also alter the textural and sensorial properties of ice creams and whipping toppings. By understanding the underlying mechanism, these critical features of a food can be more easily manipulated.
Angeliki Kourkoulakou, Anna Tasiouli, Theodoros Paschos, Effie Tsakalidou, Maria Kazou1
1Laboratory of Dairy Research, Department of Food Science and Human Nutrition, Agricultural University of Athens, Greece
Goat milk can be considered as a rich reservoir of strains with promising technological traits. Thus, in this study, strains isolated from raw goat milk, and selected on the basis of their technological properties, were evaluated as starters/adjuncts in two types of goat milk cheese. In type 1, a blend of lactic acid bacteria (LAB), namely strains of Lactococcus lactis, Lacticaseibacillus paracasei, Lactiplantibacillus plantarum and Leuconostoc mesenteroides was used, while in type 2, Lacticaseibacillus paracasei was replaced by a wild yeast strain of Debaryomyces hansenii. Milk and cheese samples during ripening were subjected to physicochemical and classical microbiological analysis, while the final products to sensory analysis as well. Microbiological analysis revealed that the total mesophilic counts and LAB initially increased and then remained stable throughout cheese ripening. As expected, yeast counts were lower in type 1 cheese compared to type 2 where the ripening yeast culture was added. No coliforms were detected, which is an indicator of the good hygiene practices followed. Both cheese types were characterized by a low pH, smooth texture and pleasant taste.
The practical relevance of this study is the exploitation of the indigenous raw goat milk microbiota as a tool towards the production of new cheeses of high quality and safety. A relevant patent application is in progress.
FrieslandCampina, The Netherlands
Ioanna Neokleous, Justyna Tarapata, Photis Papademas1
1Cyprus University of Technology, Cyprus
Halloumi cheese PDO is a white-brined cheese that is incredibly important for the economy of Cyprus and as increasing quantities of the cheese are produced, whey volumes, as a by-product of the manufacturing procedure, are also increased. Whey is often pasteurized before being further used in the cheesemaking procedure for purification purposes. UV-C photo-purification is used for the inactivation of microorganisms, but its use in highly turbid organic fluids might be challenging therefore the effect of UV-C technology on pathogens inoculated in whey-brine derived from the production of Halloumi PDO cheese, was studied.
Whey-brine (12% NaCl) was inoculated with five different pathogens; the most resistant microorganism was Listeria innocua, requiring a UV-C dosage of 320 J/L. The inactivation for the rest of the bacteria occurred at equal or less than 200 J/L dosage. The results from this study indicate that a continuous (UV-C) turbulent flow photo-purification processing system is a promising non-thermal processing method for the reduction of foodborne pathogens of turbid fluids (i.e. whey), and could replace relevant processes involving heat treatment.
Non-thermal processes are becoming even more popular in order to fulfil the demands of a sustainable production especially in the dairy industry. Studies on dairy, milk and novel non-thermal processes such as UV-C treatment, are targeting cost-efficient, minimal-processing methods in order to produce safe products while preserving the nutritional and organoleptic characteristics.
Gaurav Kr Deshwal1,2, Laura G. Gomez-Mascaraque1, Bernard Martin Corrigan1, Mark Fenelon1, Thom Huppertz2,3
1Department of Food Chemistry and Technology, Teagasc Food Research Centre, Ireland
2Department of Agrotechnology and Food Sciences, Wageningen University, The Netherlands
3FrieslandCampina, The Netherlands
The effect of emulsifying salts (ES) on the solubilization of para-κ-, αs1-, αs2-, and β-casein and minerals from 5% (w/w) rennet casein suspensions containing variable amounts of disodium phosphate (DSP) and trisodium citrate (TSC) at pH 5.8 and 6.7, and heat treatment (95°C/5 min) was studied. Casein (CN) solubilization increased with increasing ES level up to 150 mM for DSP and 50 mM for TSC. TSC was more efficient than DSP in solubilizing all the casein fractions (> 85% solubilized at 50 mM TSC) except αs2-CN. A higher amount of individual caseins were solubilized at pH 6.7 in comparison to 5.8, whereas heating reduced levels of solubilized protein regardless of pH. The amount of solubilized αs2-CN was not affected by heating, and β-CN was more susceptible to heating at pH 5.8. DSP showed a decrease and TSC showed a constant increase in soluble Ca with increasing ES amount. Thus, ES act by solubilizing casein proteins by chelation of Ca, but the extent of casein micelles dissociation depends on the type and concentration of ES, pH, and temperature. TSC chelates Ca and forms soluble complexes while DSP forms insoluble para-caseinate-Ca phosphate complexes.
The results of this study will help in elucidating the critical role of emulsifying salts in modulating casein hydration and dispersion during processed cheese manufacture and understanding their effect on the final product attributes. The knowledge gained may also establish a framework for understanding the interactions and matrix formation of casein gelation products such as processed cheese.
Lotte Juul Knudsen1,2, Søren Drud-Heydary Nielsen1,2, Ekaterina Churakova3, Valentin Rauh4, Daniel Otzen2,5, Lotte Bach Larsen1,2
1Aarhus University, Department of Food Science, Denmark
2CiFOOD Aarhus University Centre for Innovative Food Research, Denmark
3DSM Food and Beverage, The Netherlands
4Arla Foods Innovation Centre, Denmark
5Aarhus University, Interdisciplinary Nanoscience Center, Denmark
Lactose-free (LF) UHT milk has a shorter shelf-life (~6 months) than normal UHT milk (~9-12 months). In LF milk, lactose has been hydrolyzed to glucose and galactose which is more reactive in Maillard reactions compared to lactose. In addition, the lactase preparations may contain impurities such as residual proteolytic activity, which further contributes to Maillard reactions. Both mechanisms can influence the aggregation of milk proteins. This study investigates the storage stability of LF UHT milk, in relation to proteolytic side-activity, cross-links from Maillard reactions and dehydroalanine-pathway, and aggregation in the milk. Processed milk was treated with 3 different lactase preparations at a commercial UHT plant, either by pre- (lactase added prior to UHT treatment) or post-hydrolysis (lactase added after UHT treatment), and stored up to one year at 25 or 35 °C. Casein micelles were studied via Field Flow Fractionation and showed a decrease in size for all milk types during storage. A study of the residual proteolytic activity indicated proteolysis in some post-hydrolyzed samples. Finally, SDS-PAGE showed more covalent aggregation in LF milk compared to normal UHT milk.
The purpose of characterizing the storage stability of pre- and post-hydrolyzed milk added different lactase preparation is to gain insight into the molecular mechanisms occurring. This insight can be used in the design for optimal process pathways for production of the lactose-free milk.
Moorepark Food Research Centre, Teagasc, Ireland
Eoin Murphy, Lilia Ahrné, Carsten Ersch and Alan Kelly