Evaluation of bitterness in enzymatic hydrolysates of soy protein isolate by taste dilution analysis.

Although enzymatic hydrolysates of soy protein isolate (SPI) have physiological functionality, partially hydrolyzed SPI exhibits bitter taste depending on proteases and degree of hydrolysis (DH). To determine proteolysis conditions for SPI, it is important to evaluate bitterness during enzymatic hydrolysis. Taste dilution analysis (TDA) has been developed for the screening technique of taste-active compounds in foods. The objectives of the present study were to evaluate bitterness of enzyme-hydrolyzed SPI by TDA and to compare bitterness of SPI hydrolysates with respect to kinds of proteases and DH. SPI was hydrolyzed at 50 degrees C and pH 6.8 to 7.1 to obtain various DH with commercial proteases (flavourzyme, alcalase, neutrase, protamex, papain, and bromelain) at E/S ratios of 0.5%, 1%, and 2%. The DH of enzymatic hydrolysates was measured by trinitrobenzenesulfonic acid method. The bitterness of enzymatic hydrolysates was evaluated by TDA, which is based on threshold detection in serially diluted samples. Taste dilution (TD) factor was defined as the dilution at which a taste difference between the diluted sample and 2 blanks could be detected. As DH increased, the bitterness increased for all proteases evaluated. Alcalase showed the highest TD factor at the same DH, followed by neutrase. Flavourzyme showed the lowest TD factor at the entire DH ranges. At the DH of 10%, TD factor of hydrolysate by flavourzyme was 0 whereas those by protamex and alcalase were 4 and 16, respectively. These results suggest that TDA could be applied for the alternative of bitterness evaluation to the hedonic scale sensory evaluation.

Aroma extract dilution analysis of a beeflike process flavor from extruded enzyme-hydrolyzed soybean protein.

Aroma-active compounds from a beeflike process flavor, produced by extrusion of enzyme-hydrolyzed vegetable protein (E-HVP), were analyzed using aroma extract dilution analysis. The number of aroma-active compounds and the aroma intensity were increased by the addition of aroma precursors prior to extrusion. The most intense compound was 2-methyl-3-furanthiol having a cooked rice/vitamin-like/meaty aroma note. Several sulfur-containing furans, such as 2-methyl-3-(methylthio)furan, 2-methyl-3-(methyldithio)furan, and bis(2-methylfuryl)disulfide, were detected with high flavor dilution (FD) factors. Some pyrazines, such as 2-ethyl-3,5-dimethylpyrazine, 2,6-diethylpyrazine, and 3,5-diethyl-2-methylpyrazine, also had high FD factors. It is hypothesized that sulfur-containing amino acids and thiamin were important precursors in aroma formation in process flavor from E-HVP.

Development and characterization of a flavoring agent from oyster cooker effluent.

The general composition of concentrated oyster cooker effluent (OCE) was 80% moisture, 6.7% total nitrogen, 2.4% glycogen, and 8.5% ash. Optimum conditions for enzymatic hydrolysis of OCE were 50 degrees C, 2 h of reaction time, 0.1% amylase mixture (alpha-amylase plus glucoamylase), and 0.2% protease NP. Hydrolysis of OCE led to an increase in free amino acids, with taurine comprising approximately 20% of the total. Inosine monophosphate was predominant (456 mg/100 g) among nucleotides and related compounds. Enzyme hydrolysis increased extractable nitrogen by approximately 2-fold. Trimethylamine, trimethylamine oxide, and total creatinine levels were not affected by enzyme treatment. Predominant aroma-active components of enzyme-hydrolyzed OCE included 2-acetyl-1-pyrroline and 3-(methylthio)propanal. Results of this study may help alleviate the wastewater disposal problem currently caused by OCE.

Aroma-active compounds of miniature beefsteakplant (Mosla dianthera Maxim).

Volatile flavor compounds of miniature beefsteakplant (Mosla dianthera Maxim.) from Vietnam were analyzed through gas chromatography-mass spectrometry-olfactometry (GC-MS-O). Sixty-two compounds were identified by GC-MS. Of these, (+/-)-carvone and (+/-)-limonene were the most abundant, followed by (Z)-limonene oxide, beta-caryophyllene, and alpha-humulene. Twenty aroma-active compounds were detected by aroma extract dilution analysis conducted on two GC columns of different polarities (DB-5MS and DB-Wax). The most intense aroma-active compounds were linalool (floral/sweet/lemon), (-)-carvone (spearminty), and 1-octen-3-one (mushroom/earthy). Other predominant aroma-active compounds included (Z)-3-hexenol (grassy/leafy/metallic), (Z)-limonene oxide (lemon/floral), myrcene (plastic/sweet), (+)-limonene (orange/lemon), alpha-thujene (soy sauce/grassy), and (Z)-dihydrocarvone (spearminty/pepperminty). On the basis of the aroma characteristics and intensity, it was concluded that (-)-carvone was responsible for the characteristic aroma of miniature beefsteakplant.