Whey fermentation by thermophilic lactic acid bacteria. Breakdown of beta-lactoglobulin and alfa-lactalbumin

FERNANDA MOZZI; MICAELA PESCUMA; ELVIRA MARÍA HÉBERT; GRACIELA FONT DE VALDEZ

Bologna, Italia

Simposio; FoodMicro 2006: Food Safety and food biotechnology divesrity and global impact; 2006

ICFMH, IUMS, SIMTREA, University of Bologna

Whey proteins such as b-lactoglobulin (BLG) and a-lactalbumin (ALA) are an important source of essential amino acids. However, these proteins are poorly digested and have allergenic potential. Lactic acid bacteria (LAB), widely used in the fermented food industry, could be an interesting alternative to hydrolyze these proteins for improving their digestibility and reducing their allergenic content. The aim of this work was to evaluate the growth and proteolytic activity of thermophilic LAB (Lactobacillus delbruekii subsp. bulgaricus CRL 454, Streptococcus thermophilus CRL 804, and L. acidophilus CRL 636) in reconstituted whey to further develop a functional hydrolyzed whey product. Pasteurized whey (10% w/v) was inoculated (2% v/v) with active LAB cultures and incubated at 37ºC for 24 h. Cell count (cfu/ml) was determined in MRS agar plates, and lactose consumption and production of organic acids by HPLC. Proteolysis was assayed by the o-PA test and Tricine SDS-PAGE. Degradation of whey proteins was confirmed using a chemically defined medium (CDM) with pure BLG, ALA or whey protein concentrate. Proteolytic activity on these substrates was further determined using intracellular extracts from the LAB assayed. All LAB were able to grow in whey (Dlog cfu/ml: 3 after 24 h). Lactose consumption was higher (10%) for S. thermophilus CRL 804 which was the most acidifying strain (pH: 4.1, 68 mM lactic acid) after 24 h fermentation. Non of the strains used the galactose liberated during fermentation. The o-PA values ranged between 0.4 and 1.5 mmol Leu/ml. BLG and ALA were poorly (8%) degraded during whey fermentation; an increase of the hydrolysis of these proteins was observed in CDM. Interestingly, BLG was completely degraded by intracellular enzymes from all LAB assayed.