Browsing by Person "Zipori, Dor"

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Rapid acidification and off-flavor reduction of pea protein by fermentation with lactic acid bacteria and yeasts
(2024) Zipori, Dor; Hollmann, Jana; Rigling, Marina; Zhang, Yanyan; Weiss, Agnes; Schmidt, Herbert
Pea protein is widely used as an alternative protein source in plant-based products. In the current study, we fermented pea protein to reduce off-flavor compounds, such as hexanal, and to produce a suitable fermentate for further processing. Laboratory fermentations using 5% (w/v) pea protein suspension were carried out using four selected lactic acid bacteria (LAB) strains, investigating their growth and acidification capabilities in pea protein. Rapid acidification of pea protein was achieved with Lactococcus lactis subsp. lactis strain LTH 7123. Next, this strain was co-inoculated together with either the yeasts Kluyveromyces lactis LTH 7165, Yarrowia lipolytica LTH 6056, or Kluyveromyces marxianus LTH 6039. Fermentation products of the mixed starter cultures and of the single strains were further analyzed by gas chromatography coupled with mass spectrometry to quantify selected volatile flavor compounds. Fermentation with L. lactis LTH 7123 led to an increase in compounds associated with the “beany” off-flavors of peas, including hexanal. However, significant reduction in those compounds was achieved after fermentation with Y. lipolytica LTH 6056 with or without L. lactis LTH 7123. Thus, fermentation using co-cultures of LAB and yeasts strains could prove to be a valuable method for enhancing quality attributes of pea protein-based products.
Structure formation in fruit preparations by fruit fermentates produced with exopolysaccharide-forming lactic acid bacteria
(2025) Festini, Silvan; Zipori, Dor; Wallisch, Marc; Weiss, Agnes; Neidhart, Sybille; Schmidt, Herbert; Jekle, Mario
Fruit preparations are intermediate food products that are primarily used in the dairy industry for the production of fruit yogurt or frozen desserts. Typically, they are stabilized by added hydrocolloids like pectins. The objective of this study was to investigate the potential replacement of conventional stabilizers by structure-forming fermentates produced by exopolysaccharides (EPS)-forming lactic acid bacteria (LAB). Peach puree was selected as fermentation matrix. Prior to 72 h of incubation, it was inoculated with either the heterofermentative LAB strain Levilactobacillus brevis TMW 1.2112 or the homofermentative LAB strain Pediococcus parvulus strain LTH 1110, both being known to produce EPS in form of β-D-glucan. The lyophilized fermentates were applied as stabilizers to produce strawberry fruit preparations. Flow curves, viscoelastic behaviour and shear stability were measured to investigate the effect of fermentate incorporation on the rheological properties of the products. A fermentatively induced effect was observed in terms of a 1.3-fold increase in viscosity of strawberry model fruit preparations with 10 % fermentate of Lv. brevis TMW 1.2112 compared to the addition of the same dose of fermentate blank. Further, increasing the fermentate blank dose from 10 % to 15 % resulted in a 2.4-fold viscosity increase of the model fruit preparations. High shear stability was found in all model strawberry fruit preparations. However, fermentation had no clear benefit in terms of viscoelastic behaviour and shear stability of the fruit preparations. Although the fermentatively induced thickening potential was limited, production of viscosity-increasing peach fermentate with minor changes in the sugar and amino acid profiles of the fruit proved to be feasible.