Isolation of Lactococcus lactis ssp. cremoris LRCC5306 and Optimization of Diacetyl Production Conditions for Manufacturing Sour Cream

Optimizing the fermentation parameters in the Lactic Acid Fermentation of Legume-based Beverages- a statistically based fermentation

BACKGROUND

The market for beverages is highly changing within the last years. Increasing consumer awareness towards healthier drinks led to the revival of traditional and the creation of innovative beverages. Various protein-rich legumes were used for milk analogues, which might be also valuable raw materials for refreshing, protein-rich beverages. However, no such applications have been marketed so far, which might be due to unpleasant organoleptic impressions like the legume-typical "beany" aroma. Lactic acid fermentation has already been proven to be a remedy to overcome this hindrance in consumer acceptance.

RESULTS

In this study, a statistically based approach was used to elucidate the impact of the fermentation parameters temperature, inoculum cell concentration, and methionine addition on the fermentation of lupine- and faba bean-based substrates. A total of 39 models were found and verified. The majority of these models indicate a strong impact of the temperature on the reduction of aldehydes connected to the "beany" impression (e.g., hexanal) and on the production of pleasantly perceived aroma compounds (e.g., β-damascenone). Positively, the addition of methionine had only minor impacts on the negatively associated sulfuric compounds methional, dimethyl sulfide, dimethyl disulfide, and dimethyl trisulfide. Moreover, in further fermentations, the time was added as an additional parameter. It was shown that the strains grew well, strongly acidified the both substrates (pH ≤ 4.0) within 6.5 h, and reached cell counts of > 9 log10 CFU/mL after 24 h. Notably, most of the aldehydes (like hexanal) were reduced within the first 6-7 h, whereas pleasant compounds like β-damascenone reached high concentrations especially in the later fermentation (approx. 24-48 h).

CONCLUSIONS

Out of the fermentation parameters temperature, inoculum cell concentration, and methionine addition, the temperature had the highest influence on the observed aroma and taste active compounds. As the addition of methionine to compensate for the legume-typical deficit did not lead to an adverse effect, fortifying legume-based substrates with methionine should be considered to improve the bioavailability of the legume protein. Aldehydes, which are associated with the "beany" aroma impression, can be removed efficiently in fermentation. However, terminating the process prematurely would lead to an incomplete production of pleasant aroma compounds.

Characterization of a fermented dairy, sour cream: Lipolysis and the release profile of flavor compounds

Lipolysis and flavor development during fermentation of sour cream were studied by evaluating the physicochemical changes, sensory differences and volatile components. The fermentation caused significant changes in pH, viable count and sensory evaluation. The peroxide value (POV) decreased after reaching the maximum value of 1.07 meq/kg at 15 h, while thiobarbituric acid reactive substances (TBARS) increased continuously with the accumulation of secondary oxidation products. The Free fatty acids (FFAs) in sour cream were mainly myristic, palmitic and stearic. GC-IMS was used to identify the flavor properties. A total of 31 volatile compounds were identified, among which the contents of characteristic aromatic substances such as ethyl acetate, 1-octen-3-one and hexanoic acid were increased. The results suggest that lipid changes and flavor formation in sour cream are influenced by fermentation time. Furthermore, flavor compounds may be related to lipolysis such as 1-octen-3-one and 2- heptanol were also observed.

Rheological, Physicochemical, Microbiological, and Aroma Characteristics of Sour Creams Supplemented with Milk Protein Concentrate

Milk protein concentrate (MPC) is widely used to enhance the stability and texture of fermented dairy products. However, most research has focused on yogurt products, and the effects of MPC on sour cream characteristics remain unknown. Therefore, we investigated the effects of different MPC levels (0%, 1%, 2%, and 3% w/w) on the rheological, physicochemical, microbiological, and aroma characteristics of sour creams in this study. We found that MPC supplementation stimulated the growth of lactic acid bacteria (LAB) in sour creams, resulting in higher acidity than that in the control sample due to the lactic acid produced by LAB. Three aroma compounds, acetaldehyde, diacetyl, and acetoin, were detected in all sour cream samples. All sour creams showed shear-thinning behavior (n=0.41-0.50), and the addition of MPC led to an increase in the rheological parameters (η_a,50, K, G', and G″). In particular, sour cream with 3% MPC showed the best elastic property owing to the interaction between denatured whey protein and caseins. In addition, these protein interactions resulted in the formation of a gel network, which enhanced the water-holding capacity and improved the whey separation. These findings revealed that MPC can be used as a supplementary protein to improve the rheological and physicochemical characteristics of sour cream.

Development of sour cream with vegetable oils using a food emulsion stabilised by an emulsifying complex

This scientific work describes the research that aims to study the use of a finely dispersed, aggregately stable food emulsion with a mass fraction of blended oil of 50% and xanthan gum in the composition of sour cream with vegetable oils as an analogue of traditional sour cream. The samples of fat-containing fermented-milk bases as a component of sour cream with vegetable oils with a fat content of 10-20% were obtained using two methods. The first method consists in normalising the fat content of the fermented-milk base obtained by fermentation of skimmed cow's milk with a food emulsion, and the second one – is in the fermentation of a normalised mixture consisting of a food emulsion and skimmed cow's milk. When comparing the duration of fermentation of skimmed cow's milk and normalised mixtures with a fat content of 10 to 20%, it was established that in order to achieve the minimum value of the titrated acidity of the clot of 60 °T, the duration of fermentation of skimmed cow's milk is 6 hours, of a normalised mixture with a fat content of 10% – 8 hours, 15% – 12 hours, 20% – 16 hours. According to the organoleptic quality indicators, the samples of fat-containing fermented-milk bases with a fat content of 20%, obtained by two methods, had an indiscrete but unsuitable thick consistency, which was adjusted using xanthan gum. According to the organoleptic quality indicators, it was established that in order to obtain a sour cream with vegetable oils with an indiscrete and thick consistency, 0.15% of xanthan gum should be added to the fat-containing base obtained by the first method, and 0.20% – to the fat-containing base obtained by the second method. The study of determining the content of polyunsaturated fatty acids in sour cream with vegetable oils with a fat content of 20% shows an increased content of omega-3 and omega-6 fatty acids – 2.13% and 10.88%, respectively, compared to sour cream obtained by the traditional technology.

Effect of galactomannan addition on rheological, physicochemical, and microbial properties of cultured sour cream

Sour cream is a popular fermented dairy product and galactomannans are widely used in the food industry to improve texture and stability. In this study, it was investigated the effects of different galactomannans (guar gum (GG), locust bean gum (LBG), and GG/LBG) on the rheological, physicochemical, and microbial properties of sour creams. All the sour cream samples had similar pHs (4.55-4.57), acidity (0.83-0.86%), and lactic acid bacteria viable counts (8.08-8.15 log CFU/g) after fermentation. The rheological parameters (η_a,50, K, G', G″, and tan δ) of the sour creams increased after the addition of galactomannans. The sour cream with GG showed higher η_a,50, K, G', and G″ values than the sour cream with LBG. Furthermore, the combination of galactomannans (GG/LBG) did not have any synergistic effect on the sour cream. The water-holding capacity of sour creams was enhanced by the addition of galactomannans, resulting in reduced syneresis.