ARTIFICIAL RIPENING OF MAATJES-CURED HERRING WITH THE AID 

 OF PROTEOLYTIC ENZYME PREPARATIONS 



T. M. RiTSKES' 



ABSTRACT 



For manufacturing maatjes-cured herring, the herring caught in the North Sea or Irish Sea is suitable 

 only during months when the proteolytic activity of the appendices pyloricae is sufficiently high. For 

 instance, only North Sea herring caught from May to July has sufficient proteolytic activity for the man- 

 ufacture of a well-ripened product. For herring caught in other areas, this period may differ consider- 

 ably. The present work shows that it is possible to use herring caught in other seasons if protease 

 preparations are added to the fish together with salt. The herrings were examined organoleptically, 

 whereas the brines were examined by chemical analysis and by chromatography on Sephadex G-25. No 

 significant differences were found between naturally ripened herring and herring cured by the aid of 

 enzyme preparations. The lipase content of the preparation should be low enough in order to avoid the 

 formation of a fatty acid taste in the cured fish. 



Maatjes-type cured herring, the fish product that 

 has been made for centuries aboard Dutch fish- 

 ing vessels, is usually made from North Sea 

 herring (Clupea harengus L.), and in latter 

 years from Irish Sea herring as well. 



After being caught, the herring is gibbed and 

 salted promptly. "Gibbing" means the removal 

 of some of the intestines through an incision 

 below the left gill. It is essential that, at this 

 procedure, the appendices pyloricae are left in 

 the fish; according to Luijpen (1959) this organ 

 plays an important role in the formation of the 

 characteristic organoleptic properties of the 

 product. The particular taste and the soft con- 

 sistency are due to the action of proteolytic en- 

 zymes from the appendices pyloricae on the fish 

 flesh. 



Since the content of proteolytic enzymes in 

 the fish varies with the seasons, the fish is suit- 

 able for the manufacture of maatjes-cured her- 

 ring only for a few months. Other variables 

 like age and size of the fish or its source may 

 also influence the protease content and in this 

 way restrict the suitability of herring for the 

 maatjes-curing process. For these reasons, 

 there is a demand for a manufacturing method 



' Institute for Fishery Products TNO, IJmuiden, the 

 Netherlands. 



Manuscript accepted March 1971- 



FISHERY BULLETIN: VOL. 69, NO. 3, 1971. 



which is less dependent upon the protease ac- 

 tivity of the appendices pyloricae. 



The aim of our investigation was, therefore, 

 to find the conditions for obtaining an acceptable 

 maatjes-cured herring by the addition of pro- 

 tease preparations. In this way a product with 

 the desired organoleptic properties might be 

 manufactured from herring which have rel- 

 atively inactive appendices pyloricae and which 

 consequently cannot ripen in a natural way. 



MATERIALS AND METHODS 



Artificially ripened herring was made by add- 

 ing protease preparations and salt to gutted 

 fresh or frozen herring. The enzyme prepara- 

 tions were mixed with the salt before salting 

 the herring in the usual way, viz. mixing the 

 herring with a certain quantity of dry salt. 

 Shortly after the addition of salt, a brine is 

 formed which covers the fish entirely. After 

 storage from 7 to 31 days the fish was examined 

 organoleptically and the brines chemically. In 

 most cases the enzyme-treated herring was com- 

 pared with naturally ripened herring and with 

 eviscerated ("gutted") herring to which no en- 

 zyme preparations were added. 



The purpose of the chemical analyses was to 

 gather information about possible differences 



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