Meat products, which are rich in high quality proteins, provide nutrition and health benefits. However, owing to their fat, saturated fatty acid, and cholesterol content, these products are associated with cardiovascular diseases, certain types of cancer, obesity, and other issues. In addition, meat...
Meat products, which are rich in high quality proteins, provide nutrition and health benefits. However, owing to their fat, saturated fatty acid, and cholesterol content, these products are associated with cardiovascular diseases, certain types of cancer, obesity, and other issues. In addition, meat products called fermented sausages are unfamiliar in Korea. Therefore, to overcome the above limitations and improve the nutritional value and beneficial properties of fermented sausage, we evaluated the utility of using lactic acid bacteria (LAB) as functional starter cultures. Functional LAB was applied to fermented sausages to produce novel varieties of these sausages.
The results obtained are summarized below.
In chapter 1, we show that among the 305 strains of LAB isolated from kimchi samples, 11 strains were selected as starter candidates based on growth speed, pH lowering ability, and biogenic amine (BA) productivity, including gamma-amino butyric acid (GABA)-productivity. In an in vitro test, the Y8 (Lactobacillus brevis), O52 (Pediococcus acidilactici), and KA20 (Weissella halotolerans) strains produced 39.00 ± 1.36, 49.73 ± 3.80, and 64.59 ± 0.61 mg/kg of GABA, respectively. Interestingly, although isolate Y8 showed low productivity in vitro, the amount of GABA produced during in situ tests (61.30 ± 2.61 mg/kg) was similar to that produced by isolate PM3 (L. brevis), which was used as a positive control (69.64 ± 2.20 mg/kg). Therefore, isolate Y8 was selected as the functional starter culture for producing fermented sausages as it allowed safe handling, exhibited rapid growth, and produced abundant GABA.
Chapter 2 evaluates the functional properties of LAB obtained from various sources and also identifies effective strains of probiotic LAB. Ten LAB were selected and their probiotic properties such as acid resistance, bile tolerance, cholesterol assimilation activity, and adherence to Caco-2 cells were assessed. Among these, Lactobacillus curvatus R8 and Pediococcus acidilactici S18 showed complete tolerance to 0.3% bile acid. In addition, these strains showed maximum acid tolerance, with more than 106 CFU/ml bacteria persisting after 3 h incubation at pH 2.5. Furthermore, Lactobacillus curvatus R8 and Pediococcus acidilactici S18 reduced cholesterol levels by > 50% in an in vitro test. In particular, these strains showed high viable cell counts than other strains after 2 h in Caco-2 cell (ATCC number: HTB-37) adhesion assay. In in vivo experiments, four-week-old male Balb/c 50 mice were fed with normal diet (ND), a hypercholesterolemic diet (HD), HD with Lactobacillus curvatus R8 (ca. 1.0×108 CFU/ml), and HD with Pediococcus acidilactici S18 (ca. 1.0 × 108 CFU/ml) for seven weeks. Hypercholesterolemic mice treated with these isolates showed a significant decrease in total blood cholesterol and low density lipoprotein (LDL) levels. In conclusion, isolates R8 and S18 are potential starter cultures with probiotic properties that exhibit acid tolerance, bile resistance, and cholesterol-lowering activities.
In chapter 3, we determined the physicochemical, microbiological, and quality characteristics of a new type of fermented sausage manufactured by incorporating Baechu-kimchi powder and GABA-producing LAB. The LAB count was maximum by day nine of ripening of the inoculated sausages, accompanied by a rapid decrease in pH. The addition of kimchi powder decreased the lightness (L∗) and increased the redness (a∗) and yellowness (b∗) values, while significantly increasing the hardness and chewiness of the sausage (p < 0.05). Moreover, although the thiobarbituric acid reactive substance content increased in all samples during the study period, this increase was lower in the kimchi-treated samples, indicating a reduction in lipid oxidation. Overall, our results show that addition of Baechu-kimchi powder to sausages reduced the off-flavor properties and improved the taste profile of the fermented sausage in sensory evaluations. The GABA content of all fermented sausages increased from 17.42–25.14 mg/kg on the third day of fermentation to 60.95–61.47 mg/kg on the thirtieth day. These results demonstrate that Baechu-kimchi powder and GABA-producing LAB could be used as functional materials for improving quality characteristics of fermented sausage.
Meat products, which are rich in high quality proteins, provide nutrition and health benefits. However, owing to their fat, saturated fatty acid, and cholesterol content, these products are associated with cardiovascular diseases, certain types of cancer, obesity, and other issues. In addition, meat products called fermented sausages are unfamiliar in Korea. Therefore, to overcome the above limitations and improve the nutritional value and beneficial properties of fermented sausage, we evaluated the utility of using lactic acid bacteria (LAB) as functional starter cultures. Functional LAB was applied to fermented sausages to produce novel varieties of these sausages.
The results obtained are summarized below.
In chapter 1, we show that among the 305 strains of LAB isolated from kimchi samples, 11 strains were selected as starter candidates based on growth speed, pH lowering ability, and biogenic amine (BA) productivity, including gamma-amino butyric acid (GABA)-productivity. In an in vitro test, the Y8 (Lactobacillus brevis), O52 (Pediococcus acidilactici), and KA20 (Weissella halotolerans) strains produced 39.00 ± 1.36, 49.73 ± 3.80, and 64.59 ± 0.61 mg/kg of GABA, respectively. Interestingly, although isolate Y8 showed low productivity in vitro, the amount of GABA produced during in situ tests (61.30 ± 2.61 mg/kg) was similar to that produced by isolate PM3 (L. brevis), which was used as a positive control (69.64 ± 2.20 mg/kg). Therefore, isolate Y8 was selected as the functional starter culture for producing fermented sausages as it allowed safe handling, exhibited rapid growth, and produced abundant GABA.
Chapter 2 evaluates the functional properties of LAB obtained from various sources and also identifies effective strains of probiotic LAB. Ten LAB were selected and their probiotic properties such as acid resistance, bile tolerance, cholesterol assimilation activity, and adherence to Caco-2 cells were assessed. Among these, Lactobacillus curvatus R8 and Pediococcus acidilactici S18 showed complete tolerance to 0.3% bile acid. In addition, these strains showed maximum acid tolerance, with more than 106 CFU/ml bacteria persisting after 3 h incubation at pH 2.5. Furthermore, Lactobacillus curvatus R8 and Pediococcus acidilactici S18 reduced cholesterol levels by > 50% in an in vitro test. In particular, these strains showed high viable cell counts than other strains after 2 h in Caco-2 cell (ATCC number: HTB-37) adhesion assay. In in vivo experiments, four-week-old male Balb/c 50 mice were fed with normal diet (ND), a hypercholesterolemic diet (HD), HD with Lactobacillus curvatus R8 (ca. 1.0×108 CFU/ml), and HD with Pediococcus acidilactici S18 (ca. 1.0 × 108 CFU/ml) for seven weeks. Hypercholesterolemic mice treated with these isolates showed a significant decrease in total blood cholesterol and low density lipoprotein (LDL) levels. In conclusion, isolates R8 and S18 are potential starter cultures with probiotic properties that exhibit acid tolerance, bile resistance, and cholesterol-lowering activities.
In chapter 3, we determined the physicochemical, microbiological, and quality characteristics of a new type of fermented sausage manufactured by incorporating Baechu-kimchi powder and GABA-producing LAB. The LAB count was maximum by day nine of ripening of the inoculated sausages, accompanied by a rapid decrease in pH. The addition of kimchi powder decreased the lightness (L∗) and increased the redness (a∗) and yellowness (b∗) values, while significantly increasing the hardness and chewiness of the sausage (p < 0.05). Moreover, although the thiobarbituric acid reactive substance content increased in all samples during the study period, this increase was lower in the kimchi-treated samples, indicating a reduction in lipid oxidation. Overall, our results show that addition of Baechu-kimchi powder to sausages reduced the off-flavor properties and improved the taste profile of the fermented sausage in sensory evaluations. The GABA content of all fermented sausages increased from 17.42–25.14 mg/kg on the third day of fermentation to 60.95–61.47 mg/kg on the thirtieth day. These results demonstrate that Baechu-kimchi powder and GABA-producing LAB could be used as functional materials for improving quality characteristics of fermented sausage.
Keyword
#baechu-kimchi probiotics functional fermented sausage gamma-aminobutyric acid (GABA)
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