Preparation and Taste Characteristics of Kokumi N-Lactoyl Phenylalanine in the Presence of Phenylalanine and Lactate

Abstract

N-l-Lactoyl phenylalanine (N-l-lactoyl-Phe) has been identified as a taste-active contributor in many fermented foods. However, its preparation, taste property, and content in foodstuffs are little known to date. In the current study, two preparation technologies of N-l-lactoyl-Phe including heating and enzymatic methods were investigated. Other investigations include its taste property and quantification in several fermented foods. The results indicated that the heating preparation and enzymatic preparation only produced N-l-lactoyl-Phe instead of N-d-lactoyl-Phe in the presence of l-lactate/d-lactate and l-phenylalanine (Phe). A high yield (58.0% ± 0.7%) of N-l-lactoyl-Phe was achieved under the following conditions: Phe, lactate, CaO, and water at molar ratios of 1:8:0.3:9 kept at 100 °C for 3 h. With nine enzymes, a maximum yield of 21.2% ± 0.3% was achieved in the aqueous solution under mild operating conditions: 0.18 M Phe, 0.90 M lactate, 5 g/L Debitrase HYW 20, pH 8, and 55 °C for 24 h. The sensory evaluation revealed that N-l-lactoyl-Phe in water enhanced the salty and umami intensity. It also enhanced the thickness, mouthfulness, and continuity of salt solution, model broth, and chicken broth, revealing that N-l-lactoyl-Phe was a kokumi-active compound. The kokumi thresholds of N-l-lactoyl-Phe in these solutions were 50, 50, and 25 mg/L, respectively. N-l-Lactoyl-Phe was quantified in traditional Chinese fermented foods as 30.12 ± 0.28 mg/kg in preserved pickles, 14.11 ± 0.14 mg/kg in soybean paste, 4.87 ± 0.16 mg/kg in fermented bean, 0.71 ± 0.11 mg/kg in rice vinegar, and 20.34 ± 0.18 mg/kg in soy sauce. These results revealed the potential of N-l-lactoyl-Phe as a taste enhancer, presenting a new opportunity for the food industry.

Discovery of N-l-Lactoyl-l-Trp as a Bitterness Masker via Structure-Based Virtual Screening and a Sensory Approach

“…As shown in Table , the N - l -Lac- l -Trp solution after pH adjustment exhibited a kokumi-like taste with a recognized threshold of 100 mg/L, an astringent taste with a recognized threshold of 200 mg/L, and a bitter taste with a recognized threshold of 400 mg/L. In our previous study, the N - l -Lac- l -Phe aqueous solution also has a complex taste at a similar recognized threshold . As far as we can gather from the previous literature, the taste properties of N - l -lactoyl amino acid derivatives were dependent on amino acids at the N-terminus.…”

“…It was evident that N - l -Lac- l -Trp, N - l -Lac- l -Phe, and N - l -Lac- l -Tyr were the most promising stimulators for taste receptors. Previously, we found that N - l -Lac-Phe was a kokumi compound with an intrinsic complex taste in water . Accordingly, N - l -Lac- l -Trp and N - l -Lac- l -Tyr caught our attention for further taste evaluation.…”

“…A previous study showed that N - l -Lac- l -Glu (34 mg/L) and N - l -Lac- l -Gln (34 mg/L) increased the complexity and mouthfulness of the model broth, while N - l -Lac- l -Asp (74 mg/L) and N - l -Lac- l -Asn (76 mg/L) modulated the complexity only slightly . Our recent studies investigating the taste properties of N - l -Lac- l -Phe revealed that it has a pronounced kokumi-modulating effect . The kokumi-modulating effect of N - l -Lac- l -Phe, N - l -Lac- l -Glu, N - l -Lac- l -Gln, N - l -Lac- l -Asp, and N - l -Lac- l -Asn (in descending order) agree well with docking affinity in virtual screening.…”

“…Excess lactate contributed to N-L-Lac-Phe synthesis but could also have an inhibitory effect. 12 Therefore, the effect of the molar ratio of Trp and lactate on the N-L-Lac-L-Trp yield was examined. Figure 2D shows that with the exception of FoodPro 51FP, which has the highest N-L-Lac-L-Trp yield at a 1:15 molar ratio (Trp:lactate), the other three enzymes were all present at a 1:10 molar ratio.…”

“…Hofmann et al recently revealed the intrinsic taste of N - l- Lac -l -Gly, N - l- Lac -l -Ala, N - l- Lac -l -Glu, N - l- Lac -l -Gln, N - l- Lac -l -Asp, and N - l- Lac -l -Asn and added fullness, volume, and complexity to Korean kimchi . Our team also found that N - l- Lac -l -Phe from enzymatic synthesis exhibited strong kokumi properties . In addition, N - l- Lac-GMP was recognized as a new umami molecule; N - l- Lac-4-hydroxyben zylamine, N - l- Lac-vanillylamine, and N - l- Lac-dopamine were described as novel taste-modulating substances.…”