Use of Wine and Dairy Yeasts as Single Starter Cultures for Flavor Compound Modification in Fish Sauce Fermentation

Considerable amounts of fish processing byproducts are discarded each year. By developing enzyme technologies for protein recovery and modification, production of a broad spectrum of food ingredients and industrial products may be possible. Hydrolyzed vegetable and milk proteins are widely used food ingredients. There are few hydrolyzed fish protein foods with the exception of East Asian condiments and sauces. This review describes various manufacturing techniques for fish protein hydrolysates using acid, base, endogenous enzymes, and added bacterial or digestive proteases. The chemical and biochemical characteristics of hydrolyzed fish proteins are discussed. In addition, functional properties of fish protein hydrolysates are described, including solubility, water-holding capacity, emulsification, and foam-forming ability. Possible applications of fish protein hydrolysates in food systems are provided, and comparison with other food protein hydrolysates where pertinent.

Over recent decades, the average ethanol concentration of wine has increased, largely due to consumer preference for wine styles associated with increased grape maturity; sugar content increases with grape maturity, and this translates into increased alcohol content in wine. However, high ethanol content impacts wine sensory properties, reducing the perceived complexity of flavors and aromas. In addition, for health and economic reasons, the wine sector is actively seeking technologies to facilitate the production of wines with lower ethanol content. Nonconventional yeast species, in particular, non-Saccharomyces yeasts, have shown potential for producing wines with lower alcohol content. These yeast species, which are largely associated with grapes preharvest, are present in the early stages of fermentation but, in general, are not capable of completing alcoholic fermentation. We have evaluated 50 different non-Saccharomyces isolates belonging to 24 different genera for their capacity to produce wine with a lower ethanol concentration when used in sequential inoculation regimes with a Saccharomyces cerevisiae wine strain. A sequential inoculation of Metschnikowia pulcherrima AWRI1149 followed by an S. cerevisiae wine strain was best able to produce wine with an ethanol concentration lower than that achieved with the single-inoculum, wine yeast control. Sequential fermentations utilizing AWRI1149 produced wines with 0.9% (vol/vol) and 1.6% (vol/vol) (corresponding to 7.1 g/liter and 12.6 g/liter, respectively) lower ethanol concentrations in Chardonnay and Shiraz wines, respectively. In Chardonnay wine, the total concentration of esters and higher alcohols was higher for wines generated from sequential inoculations, whereas the total concentration of volatile acids was significantly lower. In sequentially inoculated Shiraz wines, the total concentration of higher alcohols was higher and the total concentration of volatile acids was reduced compared with those in control S. cerevisiae wines, whereas the total concentrations of esters were not significantly different.

Multistarter fermentations of Hanseniaspora uvarum, Torulaspora delbrueckii and Kluyveromyces thermotolerans together with Saccharomyces cerevisiae were studied. In grape musts with a high sugar content, mixed trials showed a fermentation behaviour and analytical profiles of wines comparable to or better than those exhibited by a pure culture of S. cerevisiae. Sequential trials of T. delbrueckii and K. thermotolerans revealed a sluggish fermentation, while those of H. uvarum exhibited an unacceptable increase in ethyl acetate content (175 ml l(-1)). A low fermentation temperature (15 degrees C) of multistarter trials of H. uvarum resulted in a stuck fermentation that was not due to a deficiency of assimilable nitrogenous compounds since lower amounts of these compounds were used. Sequential fermentation carried out by H. uvarum at 15 degrees C confirmed the high production of ethyl acetate. The persistence and level of non-Saccharomyces yeasts during multistarter fermentations under stress conditions (high ethanol content and/or low temperature) can cause stuck fermentations.