Flavour improvement of reduced-fat peanut butter by addition of a kokumi peptide, γ-glutamyl-valyl-glycine
© Miyamura et al.; licensee BioMed Central. 2015
Received: 11 September 2014
Accepted: 20 November 2014
Published: 26 January 2015
Recent studies have demonstrated that kokumi substances, which enhance basic tastes and modify mouthfulness and continuity although they have no taste themselves, are perceived through the calcium-sensing receptor (CaSR). Screening by a CaSR assay and sensory evaluation have shown that γ-glutamyl-valyl-glycine (γ-Glu-Val-Gly) is a potent kokumi peptide. In our previous study, it was reported that the addition of γ-Glu-Val-Gly to chicken consommé significantly enhanced mouthfulness, continuity and thickness. In this study, the effect of γ-Glu-Val-Gly on reduced-fat peanut butter was investigated.
Prior to the evaluation of the effect of γ-Glu-Val-Gly, a comparison test was conducted between full-fat model peanut butter and reduced-fat peanut butter. The sensory attributes in which the score of the full-fat model was significantly higher than that of the reduced-fat sample were used for the evaluation of the effect of γ-Glu-Val-Gly. The addition of γ-Glu-Val-Gly significantly enhanced thick flavour, aftertaste, and oiliness in the reduced-fat peanut butter.
A kokumi peptide, γ-Glu-Val-Gly, can enhance thick flavour, aftertaste and oiliness in reduced-fat peanut butter. This suggests that addition of γ-Glu-Val-Gly can improve the flavour of low-fat foods.
KeywordsLow-fat foods Reduced-fat foods Peanut butter Kokumi γ-glutamyl-valyl-glycine Sensory evaluation
Recent studies have revealed that kokumi substances such as glutathione (GSH) are perceived through the calcium-sensing receptors (CaSRs) in humans . These studies have confirmed that GSH can activate human CaSRs, as can several γ-glutamyl peptides, including γ-Glu-Ala, γ-Glu-Val, γ-Glu-Cys, γ-Glu-α-aminobutyryl-Gly (ophthalmic acid) and γ-Glu-Val-Gly. Furthermore, these compounds have been shown to possess the characteristics of kokumi substances, which modify the five basic tastes (especially sweet, salty and umami) when added to basic taste solutions or food, even though they have no taste themselves at the concentrations tested [2–8]. The CaSR activity of these γ-glutamyl peptides is positively correlated with the sensory activity of kokumi substances, suggesting they are perceived through the CaSRs in humans. Among these, γ-Glu-Val-Gly has been reported to be a potent kokumi peptide with a sensory activity 12.8-fold greater than that of GSH .
In our previous study, the effect of γ-Glu-Val-Gly on the sensory characteristics of chicken consommé was investigated. Adding γ-Glu-Val-Gly to chicken consommé significantly enhanced thickness (taste enhancement ~5 s after tasting), continuity (taste intensity at 20 s after tasting), and mouthfulness (the reinforcement of taste sensation throughout the mouth and not just on the tongue) . It is generally known that these sensations are evoked by the addition of fat-containing food materials such as dairy fat emulsion .
The problem of the increase in the obese population has resulted in various kinds of reduced-fat foods being developed and commercialised. However, in general, the palatability of reduced-fat foods is lower than that of full-fat foods. In previous studies, it has been demonstrated that the reduced-fat samples have decreased juiciness, greasiness, aftertaste, and overall flavour intensity in sausages  and decrease the score of creaminess in yogurt . In addition, it has been demonstrated that the reduced-fat samples have lower scores in thickness, smoothness, creaminess, mouth coating and milky/cooked sugar flavour in ice cream  and have lower scores in milk fat flavour and brothy flavour in cheddar cheese . To overcome these problems, because reduced-fat foods mainly lack texture, the use of thickeners such as gums, starch and modified starch has been proposed. However, the reduced-fat foods with such additives still have lower palatability than full-fat foods.
In the present study, we aimed to clarify whether addition of γ-Glu-Val-Gly changed the flavour by palatability of reduced-fat foods. We investigated the effect of γ-Glu-Val-Gly on reduced-fat peanut butter.
Results and discussion
In this study, first, the sensory attributes of peanut butter were discussed and selected by expert panellists. Then, panellists rated the differences between reduced- and full-fat peanut butter to establish how increased fat affected the sensory attributes of peanut butter. Finally, the same evaluation was conducted comparing reduced-fat peanut butter and that with kokumi peptide, γ-Glu-Val-Gly.
During the group discussion, panellists listed up the words, selected the attributes and made a consensus of the sensation which the attribute expressed. Finally, the panellists developed ten attributes: peanut flavour, saltiness, sweetness, bitterness, thick flavour (thickness of taste; the enhancement of taste intensity with maintaining the balance of taste), aftertaste (the total aftertaste intensity after 5 s of all flavour notes within the sample), continuity of taste (the taste intensity at ~20 s), smoothness, and oiliness.
Comparison between reduced-fat sample and full-fat model of peanut butter
Result of the comparison test between low-fat peanut butter and full-fat model peanut butter
Score of full-fat model
0.24 ± 0.05
0.04 ± 0.04
-0.03 ± 0.05
-0.10 ± 0.05
0.15 ± 0.06
0.16 ± 0.04
Continuity of taste
0.14 ± 0.04
0.10 ± 0.08
-0.01 ± 0.09
0.23 ± 0.07
Effect of addition of γ-Glu-Val-Gly in reduced-fat peanut butter
Effect of γ-Glu-Val-Gly on the low-fat peanut butter
Score of sample with γ-Glu-Val-Gly
0.06 ± 0.05
0.13 ± 0.04
0.14 ± 0.05
Continuity of taste
0.09 ± 0.05
0.09 ± 0.04
The previous studies described that the several reduced-fat foods and low-fat foods lacked the sensations related to ‘thick flavour’, ‘aftertaste’ and ‘oiliness’. For example, it has been previously reported that the low-fat sausage has lower juiciness and aftertaste intensity  and that low-fat yogurt has lower creaminess  than full-fat products. In addition, it has been previously reported that reduced-fat ice cream indicated lower scores of texture-related attributes such as thickness, smoothness, creaminess, mouth coating than those of full-fat products . Therefore, it is considered that the addition of γ-Glu-Val-Gly can be used to improve the flavour of other reduced-fat foods. In order to clarify this possibility, it is necessary to conduct a preference test using a consumer panel, and this test is now in progress in our laboratory. The effect of γ-Glu-Val-Gly on other reduced-fat foods is also now under investigation in our laboratory.
In this study, the effect of a kokumi peptide, γ-Glu-Val-Gly, on the flavour of reduced-fat peanut butter was investigated. The results indicated that the addition of γ-Glu-Val-Gly significantly enhanced the intensities of thick flavour, aftertaste, and oiliness. These results demonstrated that addition of γ-Glu-Val-Gly increased some sensations that were lacking in the reduced-fat peanut butter, suggesting that addition of the peptide could improve the flavour of reduced-fat peanut butter.
Preparation of γ-Glu-Val-Gly
The γ-Glu-Val-Gly used in the present study was of food additive grade (FEMA-GRAS No. 4709; Flavor and Extract Manufacturers Association (FEMA); JECFA food flavouring No. 2123; Joint FAO/WHAO Expert Committee on Food Additives (JECFA)) obtained from Ajinomoto Co. Inc. (Tokyo, Japan) and was prepared by chemical synthesis as reported previously .
Preparation of reduced-fat peanut butter and full-fat peanut butter model
Raw materials for the low-fat peanut butter and full-fat model peanut butter
Full-fat model (wt.%)
Emulsifier (sugar-ester; HLB:15)
Emulsifier (glyceryl monostearate; HLB:4)
Selection of the sensory panel
In this study, 29 panellists (17 men and 12 women; 28.8 ± 5.0 years old, mean ± standard deviation) participated in the sensory evaluation. All panellists were the employees of Ajinomoto Shanghai Food Research and Technology Center and were working on the development of foods. They were Chinese and were residents of Shanghai city. In addition, all of them passed the sensory panel examination conducted using a previously described method . For the comparison between the reduced-fat peanut butter and full-fat model, 20 panellists (9 men and 11 women; 27.6 ± 3.6 years old, mean ± standard deviation) participated in the sensory evaluation. For the investigation of the effect of γ-Glu-Val-Gly, 19 panellists (13 men and 6 women; 29.9 ± 5.3 years old, mean ± standard deviation) participated in the evaluation.
Selection of the sensory attributes
Panellists evaluated samples of the reduced-fat peanut butter and full-fat peanut butter model. A panel leader led the group in discussion on the differences and similarities between the samples. They developed a list of sensory attributes that described the sensory characteristics of the products. The panellists developed ten attributes: peanut flavour, saltiness, sweetness, bitterness, thick flavour, aftertaste, continuity of taste, smoothness, viscosity and oiliness. The panellists practiced rating the samples on the list so that they were prepared to begin data collection.
Procedure for sensory evaluation
The sensory evaluation was conducted between 10:00 am and 11:30 am in the partitioned booth at 25°C in an air-conditioned sensory evaluation room. For evaluation of the peanut butter samples, 10 g of the sample was spread on one piece of bread (10 g), which was cut into four pieces. The panellists held each piece of bread with peanut butter in the mouth, evaluated the taste, and rated each attribute. They rinsed their mouths with commercial mineral water between the samples. They completed the rating for each attribute on a three-point linear scale; -1.0: apparently weaker than the control; 0: same as the control; and 1.0: apparently stronger than the control. For comparison between the reduced-fat sample and full-fat model, half of the panellists evaluated the full-fat model using a reduced-fat sample as the control and the other half evaluated the reduced-fat sample using a full-fat model as the control. Combination of the samples was randomised and balanced. Human sensory analyses were conducted following the spirit of the Helsinki Declaration, and informed consent was obtained from all panellists. The experimental procedure was approved by the Ethics Board of the Institute of Food Sciences and Technologies, Ajinomoto.
Statistical analysis was conducted using JMP version 9.0 (SAS Institute, Cary, NC, USA). The data were collected as the means ± standard error. Data were assessed by the paired t-test. The data were considered to be significant at p < 0.05.
Flavour and Extract Manufacturers Association
The Joint FAO/WHO Expert Committee.
We sincerely thank Dr. Kiyoshi Miwa and Dr. Yuzuru Eto of Ajinomoto Co. Inc. for their encouragement and continued support of this work. We are grateful to Mr. Hiroaki Nagasaki, Mr. Toshifumi Imada, Mr. Takaho Tajima, Mr. Shuichi Jo, Mr. Keita Sasaki, and Ms. Takako Hirose of Ajinomoto Co. Inc., for their assistance. There is no funding in the present study.
- Ohsu T, Amino Y, Nagasaki H, Yamanaka T, Takeshita S, Hatanaka T, Maruyama Y, Miyamura N, Eto Y: Involvement of the calcium-sensing receptor in human taste perception. J Biol Chem 2010, 285:1016–1022. 10.1074/jbc.M109.029165View ArticlePubMed CentralPubMedGoogle Scholar
- Ueda Y, Sakaguchi M, Hirayama K, Miyajima R, Kimizuka A: Characteristic flavor constituents in water extract of garlic. Agric Biol Chem 1990, 54:163–169. 10.1271/bbb1961.54.163View ArticleGoogle Scholar
- Ueda Y, Yonemitsu M, Tsubuku T, Sakaguchi M, Miyajima R: Flavor characteristics of glutathione in raw and cooked foodstuffs. Biosci Biotech Biochem 1997, 61:1977–1980. 10.1271/bbb.61.1977View ArticleGoogle Scholar
- Ueda Y, Tsubuku T, Miyajima R: Composition of sulfur-containing components in onion and their flavor characters. Biosci Biotech Biochem 1994, 61:108–110.View ArticleGoogle Scholar
- Dunkel A, Koster J, Hofmann T: Molecular and sensory characterization of γ-glutamyl peptides as key contributors to the kokumi taste of edible beans ( Phaseolus vulgaris L.). J Agric Food Chem 2007, 55:6712–6719. 10.1021/jf071276uView ArticlePubMedGoogle Scholar
- Toelstede S, Dunkel A, Hofmann T: A series of kokumi peptides impart the long-lasting mouthfulness of matured Gouda cheese. J Agric Food Chem 2009, 57:1440–1448. 10.1021/jf803376dView ArticlePubMedGoogle Scholar
- Toelstede S, Hofmann T: Kokumi-active glutamyl peptides in cheeses and their biogeneration by Penicillium roquefortii . J Agric Food Chem 2009, 57:3738–3748. 10.1021/jf900280jView ArticlePubMedGoogle Scholar
- Nishimura T, Egusa A: Classification of compounds enhancing “koku” to foods and the discovery of a novel “koku”-enhancing compound. Jpn J Taste Smell Res 2012, 19:167–176.Google Scholar
- Flett KL, Duizer LM, Goff D: Perceived creaminess and viscosity of aggregated particles of casein micelles and κ-carrageenan. J Food Sci 2010, 75:S255-S261. 10.1111/j.1750-3841.2010.01635.xView ArticlePubMedGoogle Scholar
- Tomaschunas M, Zorb R, Fischer J, Kohn E, Hinrichs J, Busch-Stockfisch M: Changes in sensory properties and consumer acceptance of reduced fat pork Lyon-style and liver sausages containing inulin and citrus fiber as fat replacers. Meat Sci 2013, 95:629–640. 10.1016/j.meatsci.2013.06.002View ArticlePubMedGoogle Scholar
- Pimentel TC, Cruz AG, Prudencio SH: Influence of long-chain inulin and Lactobacillus paracasei subspecies paracasei on the sensory profile and acceptance of a traditional yogurt. J Dairy Sci 2013, 96:6233–6241. 10.3168/jds.2013-6695View ArticlePubMedGoogle Scholar
- Liou BK, Grun IU: Effect of fat level on the perception of five flavor chemicals in ice cream with or without fat mimetics by using a descriptive test. J Food Sci 2007, 72:S595-S604. 10.1111/j.1750-3841.2007.00494.xView ArticlePubMedGoogle Scholar
- Amelia I, Drake MA, Nelson B, Barbano DM: A new method for the production of low-fat Cheddar cheese. J Dairy Sci 2013, 96:4870–4884. 10.3168/jds.2012-6542View ArticlePubMedGoogle Scholar
- Furukawa H Proc. 7th Symp. In The Sensory Test and the Selection of Panelists. Sensory Inspection; 1977:111.Google Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.