With the recent development of the technology of producing them, pickles are much produced by manufacturers that specialize in pickles production, and the consumption of vegetables to be pickled is now increasing. The yield of vegetables varies depending on the weather and other conditions, and the supply thereof is not all the time stable. Accordingly, for pickles of summer-season vegetables such as cucumbers, etc., Japanese pickles manufacturers import salted vegetables from Southeast Asian countries such as Taiwan and Thailand in which summer-season vegetables can be cropped any time throughout the year, and they produce pickles from the thus-imported salted vegetables. The amount of salt added for salting vegetables varies depending on the type of the vegetables and on the period of time for which the salted vegetables shall be stored, but generally from a viewpoint of preventing the decomposition of vegetables by propagation of microbes and securing preservation stability, the amount of salt is extensive, because a high degree of salinity is needed. Therefore, in the process of producing pickles from such salted vegetables, the salted vegetables must be desalted and desalting them requires a large-scale apparatus and much water.
With the recent increase in health-oriented consumers, the consumption of lightly-salted pickles such as those lightly preserved in salt, for example, those lightly salted overnight rises. Concretely, the output of vegetables lightly preserved in salt now amounts to ⅓ of the overall output of pickles in Japan, but in the production of such lightly-salted pickles, the quality maintenance against microbial degradation is the most serious problem. Microbial degradation of lightly-salted pickles includes rancidity, cloudiness and bag expansion, and these are caused by the propagation of microbes such as lactic acid bacteria and yeast. Accordingly, in production of lightly-salted pickles, it is a matter of importance how to prevent the propagation of such microbes.
On the other hand, in production of lightly-salted pickles, the troublesome lactic acid bacteria and yeast are bearing the important role for brewing peculiar fermentation taste in manufacture of the pickles of others including fermentation pickles. However, if the pickles are too much fermented, their sour taste will be too strong and their smell will change and, as a result, their quality will lower.
As so mentioned hereinabove, microbes must be most optimally controlled in producing pickles, or that is, it is a matter of great importance how to control the activity of microbes in accordance with the type of pickles to be produced. Given that situation, it is desired to provide a method of surely controlling microbes in producing pickles in a simplified manner.
In this connection, it has heretofore been known that allyl isothiocyanate (hereinafter referred to as AIT), one component of wasabi (Japanese horseradish) is highly antimicrobial against colibacillus and yeast, and is therefore useful for a food freshness-keeping agent. However, AIT is an oily liquid that has a peculiar pungent smell and is highly volatile, and is therefore difficult to handle. Accordingly, if AIT is used for antimicrobial purpose in producing pickles, the composition that contains AIT must be highly soluble in water and its use must be simple. JP-A No. 6-192018 discloses an antimicrobial composition that comprises AIT, a polyhydric alcohol and a surfactant, and it says that the composition is used for processing pickles. However, the composition is powdery and is not always satisfactory in point of its solubility in water. In addition, the composition must be metered every time when a desired amount of AIT is dissolved in seasoning for pickles, and therefore, there is still room for improving the handlability of the AIT-containing composition.
For keeping the freshness of pickles and other various foods, AIT alone may have a satisfactory antimicrobial spectrum in some cases and is therefore effective by itself for microbiostatic action in pickles and others, but in some other cases, AIT alone is not satisfactory. Taking the cases into consideration, it is desirable to combine AIT with any other different type of antimicrobial component for enlarging the antimicrobial spectrum.
It is well known from the past that a hop extract has an antimicrobial activity, and it is said that a hop extract gives a peculiar bitter taste to beer and retards the growth of microbes in beer. The antimicrobial activity of the hop extract generally results from the bitter component of hops, alpha acids (humulones) and beta acids (lupulones); and the antimicrobial activity of the beta acids against lactic acid bacteria is higher than that of alpha acids against them. However, the antimicrobial spectrum of the hop extract alone is not always satisfactory.
In consideration of the above-mentioned matters, the present invention is to provide a process for stably producing pickles of good quality while taking suitable measures for surely suppressing the growth of microbes in producing pickles in a simplified manner, and to provide an antimicrobial composition that is useful as a food freshness-keeping agent free from all the problems with conventional AIT and hop extract each other.