Ten commercial proteases (neutral and alkaline) were evaluated for hydrolysis of crayfish processing by-products (CPBs). Hydrolysis conditions were optimized for the alkaline protease OptimaseTM APL-440 by response surface methodology (RSM). Two model equations were proposed with regard to effects of pH, temperature (T), time (t), enzyme/ substrate (E/S) ratio, and substrate concentration (S) on the amount of 0.3M TCA soluble peptides (TSP) and degree of hydrolysis (DH). Interaction effects between pH and T were observed (p

The aroma components of muscadine (Vitis rotundifolia Michx) grape juice were analyzed by gas chromatography (GC)/mass spectrometry and GC/olfactometry (aroma extract dilution analysis). 2,5-Dimethyl-4-hydroxy-3(2H)-furanone (furaneol), with a burnt sugar-like aroma, was the most intense aroma in the juice. Other predominant compounds included 2,3-butanedione, ethyl butanoate, ethyl 2-methylbutanoate, 2-phenylethanol, and o-aminoacetophenone. These compounds were described as buttery/cream cheese, bubble gum/fruity, green apple/fruity, rosy, and foxy, respectively. Furaneol and o-aminoacetophenone were thought to be responsible for characteristic candy and foxy-like aroma notes of muscadine grape juice. Flavor dilution chromatograms were similar for juices prepared from grapes harvested on different dates and from different locations.

Free and glycosidically bound volatile compounds were isolated and identified from muscadine grape juice. Most abundant in free and bound form was the m u s c a d i n e c h a r a c t e r -i m p a c t a r o m a c o m p o u n d 2,5-dimethyl-4-hydroxy-3(2H)-furanone (Furaneol). Other aroma compounds, such as o-aminoacetophenone and 2-phenylethanol were found in free and bound forms. A high level of 2-phenylethanol was in the glycoside form and many bound monoterpenes were identified. p-Vinylguaiacol, a potential off-flavor in muscadine juice was found at a low level in bound form. Enzymatic hydrolysis of glycoside precursors could lead to release of volatile compounds with both potentially positive and deleterious effects on the overall aroma.

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.