F.ITSKES: ARTIFICIAL RIPENING OF MAATJES-CURED HERRING 



Table 6. — Chemical analyses of the brines' in experiment 

 on artificial ripening of lean herring. 



^ The salt content in the brines was 16 ± 2% w/v. 



An addition of 0.5 g of CH 32/67 A per kg 

 of herring is too low to obtain a well-ripened 

 product under these conditions. An addition of 

 1.0 g per kg, however, seems somewhat too high. 

 A suitable dose is probably the amount of pro- 

 tease that corresponds with a proteolytic activity 

 of 2000 mg-eq NF XIII powder per kg of herring. 



In the brines (b) and (d) the same amino- 

 N contents were found, but the biuret value in 

 (d) was considerably higher than in (b). This 

 suggests that the action of the enzyme prepa- 

 ration is particularly the breakdown of muscle 

 protein to larger fragments, whereas the en- 

 dogenous enzymes show more peptidase activity. 

 This is in accordance with the observation that 

 an overdose of the enzyme preparation results 

 in a very soft rather than in a strong-tasting 

 herring. 



SUMMARY 



The addition of a certain quantity of a protease 

 preparation to herring which is unsuitable for 

 maatjes curing has a favorable effect on both 

 flavor and texture of the herring. 



An addition of 2000 mg-eq NF XIII powder 

 per kg of herring is pi'oposed. Doubling or 

 halving this amount had a pronounced effect on 

 the organoleptic properties of the cured herring. 

 The lipase activity should be low. 



In the brines the biuret value, the total N 

 content and the amount of amino N increase 

 gradually. There appears to be a distinct re- 

 lation between the biuret value in the clarified 

 brine and the consistency of the herring; the 

 same is true for the amino N content in the brine 

 and the flavor of the herring. 



The ratio biuret value: amino N content 

 found in the brine was higher for artificially 

 ripened herring than for the naturally ripened 

 product. This finding indicates that the enzyme 

 preparations are poorer in peptidase activity 

 than the appendices pyloricae from the herring. 



The protein breakdown in the artificially ri- 

 pened herring, however, does not seem to be 

 essentially diff'erent from that in the naturally 

 ripened herring. The patterns obtained by 

 chromatography of the brines over Sephadex 

 G-25 did not show any essential diflference. 



ACKNOWLEDGMENTS 



The author wishes to thank A. Ruiter and 

 L. G. Heeringa for their valuable assistance in 

 writing the manuscript. 



Table 7. — Results of organoleptic evaluations and chemical analyses from experiment on artificial ripening of 

 fresh lean herring with different amounts of a protease preparation. 



Variation 



Organoleptic evaluation 



Gutted 



Gibbed 



Gutted + 0.05% CH 32/67 A 



Gutted + 0.10% 



Gutted + 0.20% 



Gutted -I- 0.50% 



Chemical analyses of brines^ 



Biuret value 



' The salt content in the brines was 12 ± 1% w/' 



Total N 



653 



