Imène Ferroukhi1, Cécile Bord1, Sylvie Alvarez2, Karine Fayolle1, Sebastien Theil1, René Lavigne1, Christophe Chassard1, Julie Mardon1
1 Université Clermont Auvergne, INRAE, VetAgro Sup, UMRF 545 Fromage, France
2 Département qualité et économie alimentaire, VetAgro Sup, France

Abstract
Blue-veined cheeses has a specific matrix that evolves during ripening and gives an authentic typicity to finished products. The aim of this work was to characterise, for the first time, the different physico-chemical, biochemical, nutritional, microbiological and sensory variations that occur in different regions of the cheese during the ripening of Bleu d'Auvergne. Cheeses were manufactured, ripened and sampled on three regions at 2, 6, 13, 21 and 34 days of ripening. An exchange of Na and Ca ions between the different regions of cheese with a significant increase in proteolysis, yeasts and moulds was observed during ripening. Cheeses contained a high salt content (2.87%) and a significant level of Calcium (6.14 g/kg) and B12 vitamin (1.14 µg/100 g). Vitamin B2 and B6 contents increased during ripening while B9 did not change. Lactococcus and Streptococcus, were predominant and correlated with B-vitamins levels. In conclusion, B vitamins content of Bleu d'Auvergne, is interesting and the link with bacterial composition should be considered in a nutritional optimisation approach. Also, the high salt content of this cheese should be investigated in order to meet health guidelines.

Practical Relevance
The composition in calcium and B vitamins represent an important data on the nutritional composition of Bleu d'Auvergne. Opitimisation pathways are possible by studying the relationship between the bacterial community able to synthesise B vitamins. The presence of a significant salt content should also be investigated.

Inge Gazi1,2, Vojtech Franc1,2, Sem Tamara1,2, Martine P. van Gool3, Thom Huppertz3,4, Albert J. R. Heck1,2
1 Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, The Netherlands
2 Netherlands Proteomics Center, The Netherlands
3 FrieslandCampina, The Netherlands
4 Department of Agrotechnology and Food Sciences, Wageningen University, The Netherlands

Abstract
We investigated protein glycation in a complex milk system under controlled conditions representative of real-life consumer products, analysing intermediate and final products from skim milk powder production, and aged powder samples. We combined protein-centric LC-MS(/MS) with peptide-centric multi-protease LC-MS/MS focusing on the six most abundant bovine milk proteins. This strategy resulted in the identification of glycated proteoforms and of the extent of glycation per protein, high protein sequence coverage, and identification and relative occupancy of the glycation sites. We identified new glycation hot-spots additionally to the ones already described in literature. Primary sequence motif analysis revealed that glycation hot-spots were preceded N-terminally by a stretch rich in basic amino acids, and followed C-terminally by a stretch enriched in aliphatic and hydrophobic amino acids. Our study considerably extends the current understanding of milk protein glycation, discussing glycation hot-spots and their localization in relation to the primary sequences and higher-order protein structures.

Practical Relevance
Protein glycation is relevant to the dairy industry, because it is accelerated by thermal processing, and it continues to develop during storage. Furthermore, glycated proteins exhibit altered susceptibility to digestive proteases, and decreased bioavailability of the glycated amino acids. We provide further insight into the mechanism of reaction, revealing a preferential protein glycation motif.

Athanasios Limnaios1, Nausika Korialou1, Anastasia Zerva2, Maria Tsevdou1, Evangelos Topakas2, Petros Taoukis1
1 Laboratory of Food Chemistry & Technology, School of Chemical Engineering, National Technical University of Athens, Greece
2 Laboratory of Biotechnology, School of Chemical Engineering, National Technical University of Athens, Greece

Abstract
Greek yoghurt is a popular dairy product of high nutritional value. Its production has raised by-products management issues, related to the large amounts of acid whey (AW) that have proven conventional waste treatment facilities problematic. Innovative and efficient processes are sought for AW valorization. In this context, prebiotic galactooligosaccharides (GOS) could be enzymatically synthesized, via the alternative exploitation of novel β-galactosidases.

In this research, GOS production catalyzed by a novel, in-house produced β-galactosidase from Thermothielavioides terrestris was studied in relation to lactose concentration, enzyme load, pH value and temperature. Reaction products were analyzed via High Performance Anion Exchange Chromatography with Pulsed Amperometric Detection.

For results quantification, GOS yield was expressed as the percentage of total GOS concentration to initial lactose concentration. Maximum GOS yield (20.7%) was achieved using concentrated AW with 20% w/v lactose, after 10 h of enzymatic reaction at the optimum conditions for the novel β-galactosidase (50°C, pH = 4.5). Synthesized GOS were mainly di-, tri-, and tetra-saccharides.

Practical Relevance
The optimum biocatalysis conditions for GOS synthesis were explored for the novel, thermophile β-galactosidase, capable of producing GOS at conditions that allow simultaneous AW concentration. The proposed AW valorization into high added value products is compatible to the circular economy philosophy, turning the management of a high volume by-product from an environmental issue to an opportunity.

Peter Habermehl, Stefan Nöbel, Jan Fritsche1
1Max Rubner‐Institut, Department of Safety and Quality of Milk and Fish Products, Kiel, Germany

Abstract
Ultrafiltration (UF) is well established in upstream processing of the production of fermented milks. A novel combination of UF and (ceramic) nanofiltration (NF) aims to separate lactose from milk already before fermentation. Using combinations of UF–NF allowed to adjust the protein-lactose ratio and absolute lactose content of the milk base independently and without fortification. A low lactose content (<2.5 g/100g) had a significant effect on the acidification rate during lactic acid fermentation and, thus, on the microstructure of yogurt. Yogurt with the lowest lactose content (< 1.5 g/100g) needs approx. 15 h for acidification (pH < 4.6), whereby mainly the lag phase was prolonged. The viscosity at low shear-rates (<10 1/s) of the stirred yogurt significantly increased with decreased lactose content. A low lactose content favored the denaturation of whey proteins, resulting in a firmer milk gel at the same protein content. The optimum protein-lactose ratio is determined by rheological (apparent viscosity and gel firmness) and sensorial parameters. Based on preliminary trials, the optimum lactose content was assumed to be 1.5 and 2.5 g/100g.

Practical Relevance
The UF-NF combination provides a cost-efficient opportunity to adjust the protein-lactose ratio of milk without fortification. Milk proteins are retained and can be used to modify the yogurt microstructure. Reducing the native lactose content allows to optimize the sweetness by added sugars and therefore represents an opportunity for innovation and reformulation of fermented milk-products.

Carsten Nachtigall, Ramona Plebst, Georg Surber, Harald Rohm, Doris Jaros¹

_{¹ Chair of Food Engineering, Institute of Natural Materials Technology, Technische Universität Dresden, Germany}

Abstract
Acid whey with its high lactic acid content is a by-product of acid coagulation for which the industry has struggled to find a value-added application. Common approaches such as separation of ingredients are still challenging because of, e.g., membrane fouling, thus fermentation with microorganisms that possess QPS/GRAS status might be another possibility. The aim of this study is to ferment acid whey with lactate-metabolizing, mesophilic propionic acid bacteria that are able to produce viscosity-enhancing exopolysaccharides (EPS).

Ultrafiltration permeate concentrate (dry matter: 12 g/100 g) supplemented with different nitrogen sources (e.g., tryptone) was used as model substrate. To enable growth, it was necessary to adjust the pH to 6.0 prior to fermentation. Acidipropionibacterium acidipropionici DSM4900 produced ropy EPS and increased viscosity of the cell-free supernatant by Δη = 1.08 mPa∙s, whereas Propionibacterium freudenreichii PF12 produced non-ropy EPS but was able to metabolize lactate completely.

Practical Relevance
Fermentation with safe microorganisms presents a new approach for adding value to acid whey (permeates) and reducing its lactate content. The EPS-functionalized whey upon concentration can be used as ingredient in dairy products to improve their texture and avoid the use of commercial hydrocolloids.