不同空气暴露条件下四川泡菜的品质变化及产植物细胞壁降解酶微生物分析

以四川泡菜为研究对象,通过发酵坛口暴露、间歇暴露和封闭三种空气暴露程度模拟不同的空气暴露情况,探究不同空气暴露条件下四川泡菜发酵过程中的品质变化,并分析产植物细胞壁降解酶(Plant cell wall degradation enzymes,PCWDEs)的主要微生物种类。结果表明:发酵8 d后不同空气暴露条件下四川泡菜都具有该条件下的最佳质构,发酵前16 d,三种条件下四川泡菜的pH都迅速下降至3.0,总菌和乳酸菌数量都呈现先上升后下降的趋势。随着发酵时间的增加,不同空气暴露条件下四川泡菜的品质出现差异,发酵64 d后暴露式发酵四川泡菜的pH上升至6.5,真菌数量上升至7.6 lg CFU/mL,和发酵8 d相比泡菜硬度和脆度分别下降了93.2%和100%,泡菜发生明显软腐,在该条件下分离得到的19株(其中有12株为发酵48 d时分离得到)产PCWDEs微生物多为好氧型微生物;间歇暴露式发酵四川泡菜在发酵64 d后pH上升至3.5,和发酵8 d相比泡菜硬度和脆度分别下降了39.1%和35.6%,泡菜出现轻微腐败,在该条件下分离得到的6株产PCWDEs微生物多为好氧型微生物;封闭式发酵四川泡菜在发酵64 d后pH仍维持在3.0,乳酸菌数量虽下降至5.34 lg CFU/mL,但仍是四川泡菜中的主导微生物,和发酵8 d相比泡菜硬度和脆度分别下降了52.5%和24.4%,在该条件下分离得到的5株产PCWDEs微生物多为兼性厌氧型微生物。     

Improving the quality of Sichuan pickle by adding a traditional Chinese medicinal herb Lycium barbarum in its fermentation

Sichuan pickle is a traditional Chinese food fermented mainly by lactic acid bacteria (LAB). In this study, effect of adding Lycium barbarum on Sichuan pickle fermentation was investigated using kinetic modelling and correlation analysis. It was found that L. barbarum addition not only increased the amount of LAB, the total acid content and antioxidant capacity, but also improved the organoleptic quality and reduced nitrite content of the pickle considerably. Model‐based analyses revealed that L. barbarum addition increased the growth rate and decreased the death rate of LAB. The increase in antioxidant capacity of the pickle, especially the phenolics, can at least partly be attributed to its transferring from the L. barbarum. Correlation analysis results suggest that the nitrite reduction in pickle is closely related with pH value decrease and the increase in acids, and LAB, yeast and acids may all make contribution to the antioxidant capacity of the pickle.     

Preservation of Acidified Cucumbers with a Natural Preservative Combination of Fumaric Acid and Allyl Isothiocyanate that Target Lactic Acid Bacteria and Yeasts

ABSTRACT: Without the addition of preservative compounds cucumbers acidified with 150 mM acetic acid with pH adjusted to 3.5 typically undergo fermentation by lactic acid bacteria. Fumaric acid (20 mM) inhibited growth of Lactobacillus plantarum and the lactic acid bacteria present on fresh cucumbers, but spoilage then occurred due to growth of fermentative yeasts, which produced ethanol in the cucumbers. Allyl isothiocyanate (2 mM) prevented growth of Zygosaccharomyces globiformis, which has been responsible for commercial pickle spoilage, as well as the yeasts that were present on fresh cucumbers. However, allyl isothiocyanate did not prevent growth of Lactobacillus plantarum. When these compounds were added in combination to acidified cucumbers, the cucumbers were successfully preserved as indicated by the fact that neither yeasts or lactic acid bacteria increased in numbers nor were lactic acid or ethanol produced by microorganisms when cucumbers were stored at 30 °C for at least 2 mo. This combination of 2 naturally occurring preservative compounds may serve as an alternative approach to the use of sodium benzoate or sodium metabisulfite for preservation of acidified vegetables without a thermal process.     

Mechanism of Salmonella reduction in fermented pig feed

To protect consumers from Salmonella infection acquired through the consumption of pork meat, it is necessary to eradicate Salmonella from pork. In order to achieve this, the whole pork production chain should be free from Salmonella, including the pigs at the farm. In epidemiological studies it was concluded that the use of fermented feed plays a significant role in the reduction of Salmonella prevalence in pig farms. However, the mechanism of Salmonella reduction in fermented feed is not known. A controlled feed fermentation was performed using a pure culture of Lactobacillus plantarum. pH reduction, organic acid profiles and bacterial counts were determined. In L plantarum‐fermented feed, lactic acid and acetic acid were produced and the pH dropped to a value below 4.0. Antimicrobial products (bacteriocins) could not be detected. The results showed that the produced lactic and acetic acid and the pH in the feed are responsible for Salmonella reduction in fermented feed. L plantarum did not show any other antimicrobial effect on Salmonella. © 2000 Society of Chemical Industry     

Microbial and chemical changes in 'Sobrasada' during ripening

‘Sobrasada’ is a raw-cured product typical of Mallorca (Balearic Islands). Throughout its ripening process the product, like other raw-cured sausages, undergoes a series of chemical and microbial changes which lead to the formation of its desirable final characteristics.In the ‘sobrasada’ studied, the breeds, feeding and casings used in the Balearic Islands were employed. The evolution of different groups of microorganisms was followed: mesophylic aerobic microorganisms, lactic acid bacteria, Enterobacteriaceae, yeasts and moulds, group D Streptococcus, proteolytic microorganisms and lipolytic microorganisms. It was found that the predominant flora, from the beginning to the end, was made up of lactic acid bacteria. Conversely, Enterobacteriaceae disappeared as ripening went on, and the rest of the microbial groups studied underwent little variation along the process.An important characteristics of the product is the fast fall of pH, from values near 6·0 to values around 5·3, in the first week.     

An investigation into the formation of fumaric acid in apple juice concentrates

 In this study, apples inoculated with pure cultures of Rhizopus stolonifer, Penicillium expansum and Lactobacillus plantarum were utilised as the raw material to produce apple juice concentrate. The effects of microorganisms and various processing treatments on the fumaric acid, lactic acid and patulin contents of apple juice were investigated. R. stolonifer was found to be the most responsible causative agent of fumaric acid and lactic acid. L. plantarum also produced certain amounts of lactic acid, but not as much as R. stolonifer. L. plantarum caused a significant decrease in L-malic acid content indicating the occurrence of malolactic fermentation. During this complicated biochemical pathway, a small amount of fumaric acid was also formed by L. plantarum. P. expansum produced only patulin, but did not affect the fumaric acid and lactic acid contents. Fumaric acid contents of the samples decreased throughout the processing steps excepting evaporation. The fumaric acid contents of the samples increased just after evaporation depending on the heat applied. The patulin and lactic acid contents of the samples also showed a decreasing trend throughout processing. However, L. plantarum caused a significant increase in lactic acid content just after depectinization depending on whether the appropriate time-temperature conditions for incubation were available during depectinization. Received: 3 November 1998 / Revised version: 4 January 1999     

Utilization of <Emphasis Type="Italic">Echium amoenum</Emphasis> Extract as a Growth Medium for the Production of Organic Acids by Selected Lactic Acid Bacteria

Gol-gavzaban (Echium amoenum Fisch. & Mey.) is an indigenous herbal plant, related to the Boraginaceae family, cultivated historically in Iran. In this study, the suitability of Echium extract as a raw material for production of fermented juice by four strains of lactic acid bacteria (Lactobacillus paracasei, Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus delbrueckii) was examined. Echium extract was inoculated with these bacteria and incubated at 30 °C for 24 h. Changes in microbial population, pH, acidity, sugars, and organic acids metabolism were measured during the fermentation process. Results showed that all of the selected bacteria were capable to grow well in Echium extract without any supplementation. They all metabolized sugars including glucose, fructose and sucrose simultaneously. L. paracasei showed more affinity to sugar consumption at almost 45.2%, 38%, and 21.6% of initial glucose, fructose, and sucrose concentration, respectively. Lactic acid was produced immediately after the fermentation started. L. plantarum, L. delbrueckii, and L. acidophilus produced 6.8, 6.6, and 6.4 g/l lactic acid, respectively, which were significantly higher than that produced by L. paracasei (5 g/l). On the other hand in the case of acetic acid, L. paracasei produced significantly greater quantities in comparison with other strains (4.48 g/l). It was proved that E. amoenum was a desirable media for the production of some organic acids by all these bacterial strains.     

Effects of selected lactic acid bacteria on the characteristics of amaranth sourdough

BACKGROUND: As the processing of amaranth in baked goods is challenging, the use of sourdough fermentation is a promising possibility to exploit the advantages of this raw material. In this study the fermentation properties of Lactobacillus plantarum, Lactobacillus paralimentarius and Lactobacillus helveticus in amaranth‐based sourdough were examined in order to validate them as starter cultures. pH, total titratable acidity (TTA) and lactic/acetic acid ratio of the sourdough and sensory properties of the resulting wheat bread were evaluated using fermentation temperatures of 30 and 35 °C. RESULTS: While fermentation pH, TTA and lactic acid concentration showed small variations with the use of L. plantarum and L. paralimentarius, L. helveticus reached the most intensive acidification after initial adaptation to the substrate. Acetic acid production was independent of lactic acid metabolism. Furthermore, the lactic/acetic acid ratio exceeded recommendation by 10–35 times (fermentation quotient 25–82). Sensory evaluation showed no significant differences between the two fermentation temperatures but differences among the three micro‐organisms. CONCLUSION: The results provide relevant information on the fermentation properties required of a customised starter for amaranth flour. Copyright © 2010 Society of Chemical Industry     

Development of fermented instant Chinese noodle using Lactobacillus plantarum

A new-type of instant Chinese noodle was developed with the application of lactic acid fermentation by lactobacilli. Since the pH value of the noodle sheets is alkaline with kansui (around 8.5), alkaline tolerance is required for the lactobacilli to ferment noodle sheets. The screening of the lactobacilli strains suitable for the fermentation was conducted using 46 strains from 12 species (including subspecies) of lactobacilli. Several strains of Lactobacillus pentosus and Lactobacillus plantarum were found to be fermenters. Among these, L. plantarum NRIC 0380, that showed the highest fermentation rate and favorable modification of noodle, was selected as the best strain, and was employed for the pilot scale manufacture of instant Chinese noodle. During fermentation, L. plantarum NRIC 0380 produced lactic acid to about 11 g/kg noodle sheet after 24 h with a concomitant pH decrease from an initial of about 7.9 down to 3.9. Sensory test after rehydration with boiled water revealed that the fermented instant Chinese noodle sheets at pH 7.5 had increased hardness, elasticity and light sour taste.     

Biochemical changes during the preservation stage of ripe olive processing

The influences of initial sodium chloride (6% and 0% w/v in tap water) and acetic acid concentrations (0.3%, and 0.6% v/v), use of starter culture, and aerobic versus anaerobic conditions on the biochemical changes that take place throughout the preservation stage of ripe olive processing were investigated. Glucose, fructose and sucrose were completely consumed during preservation. Mannitol and malic acid were metabolized only in the presence of lactic acid bacteria or oxidative yeast (aerobic treatment). The main metabolites produced were lactic and acetic acid in aerobic or anaerobic treatments inoculated with Lactobacillus plantarum. Methanol and ethanol were present in all the brines although in a lower concentration when conditions were aerobic. Thus, induced lactic fermentation led to the most efficient utilization of carbohydrates and yielded the most suitable physicochemical characteristics for ripe olive preservation.     

Microbiological and physicochemical characterisation of green table olives of Halkidiki and Conservolea varieties processed by the Spanish method on industrial scale

The microbiological and physicochemical changes of industrially fermented Halkidiki and Conservolea green table olives were determined. Samples were analysed to monitor the population of lactic acid bacteria (LAB), yeasts and Enterobacteriaceae, together with changes in pH, acidity, salinity, colour, lactic acid, acetic acid and ethanol. LAB and yeast species diversity was evaluated at the beginning (1 day), middle (75 days) and final (135 days) stages of fermentation by RAPD-PCR genomic fingerprinting. Results revealed vigorous lactic acid processes as indicated by the dominance of LAB over yeasts. No Enterobacteriaceae could be detected after 30 days. Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) dominated in the beginning of fermentation in both varieties. In the end, Lactiplantibacillus pentosus (formerly Lactobacillus pentosus) and Pediococcus ethanolidurans prevailed in Halkidiki and Conservolea varieties, respectively. As for yeasts, Kluyveromyces lactis/marxianus and Pichia manshurica prevailed at the onset of fermentation in Halkidiki and Conservolea varieties, whereas in the end Pichia membranifaciens dominated in both varieties.     

The effect of Lactobacillus buchneri 40788 or Lactobacillus plantarum MTD-1 on the fermentation and aerobic stability of corn silages ensiled at two dry matter contents

Whole-plant corn was harvested at 33 (normal) and 41% (moderately high) dry matter (DM) and ensiled in quadruplicate 20-L laboratory silos to investigate the effects of Lactobacillus buchneri 40788 (LB) or L. plantarum MTD-1 (LP) alone, or in combination, on the fermentation and aerobic stability of the resulting silage. Aerobic stability was defined as the amount of time after exposure to air for the silage temperature to reach 2°C above ambient temperature. The chopped forage was used in a 2 × 2 × 2 factorial arrangement of treatments: normal and moderately high DM contents, LB at 0 (untreated) or 4 × 10⁵ cfu/g of fresh forage, and LP at 0 or 1 × 10⁵ cfu/g. After 240 d of ensiling, corn silage harvested at the moderately high DM had higher pH, higher concentrations of ethanol, and more yeasts compared with the silage ensiled at the normal DM content. Inoculation with LB did not affect the concentration of lactic acid in silages with a moderately high DM, but decreased the concentration of lactic acid in the silage with normal DM. Higher concentrations of acetic acid were found in the silage treated with LB compared with those not treated with this organism. Inoculation with LP increased the concentration of lactic acid only in the silage with the normal DM content. The concentration of acetic acid was lower in silage treated with LP with a moderately high DM content, but greater in the silage treated with LP with the normal DM content when compared with silages without this inoculant. Appreciable amounts of 1,2-propanediol (average 1.65%, DM basis) were found in all silages treated with LB regardless of the DM content. The addition of L. buchneri increased the concentration of NH₃-N in silages but the addition of L. plantarum decreased it. Aerobic stability was improved in all silages treated with LB, with greater aerobic stability occurring in the silage with moderately high DM compared with silage with normal DM content. Inoculation with LP had no effect on aerobic stability. There were no interactions between L. buchneri and L. plantarum for most fermentation products or aerobic stability of the silages. This study showed that inoculating whole-plant corn with L. buchneri 40788 or L. plantarum MTD-1 has different beneficial effects on the resulting silage. There appear to be no major interactions between these organisms when added together to forage. Thus, there is potential to add both organisms simultaneously to improve the fermentation and aerobic stability of corn silage.     

GROWTH OF AEROBIC WILD YEASTS

Wild yeasts of the genera Debaryomyces, Hansenula and Pichia are commonly considered to be associated with spoilage only under aerobic conditions. However, in pure cultures in either wort or a synthetic medium of yeast nitrogen base + 10% glucose, yeasts of these genera grew as well as a brewing strain of Saccharomyces cerevisiae under anaerobic conditions. Growth of S. cerevisiae was increased by the addition of unsaturated fatty acid (Tween 80) or ergosterol to the medium for anaerobic culture. No equivalent requirement was observed for the wild yeasts examined. Indeed, growth of the wild yeasts was often reduced by the addition of Tween 80, which as a surfactant prevented formation of the surface film of growth. Even under anaerobic conditions, these yeasts grew best with a surface pellicle. Although capable of good anaerobic growth in pure culture, growth of the wild yeasts was suppressed under anaerobic conditions in mixed culture with S. cerevisiae, simulating a contaminated brewery fermentation. However, the contaminants competed successfully with S. cerevisiae under aerobic conditions. There was no evidence of a “killer” effect, but prevention of pellicle formation, or production of inhibitory levels of pH or ethanol under anaerobic conditions could explain the suppression of wild yeasts under anaerobic fermentation conditions.     

Microbiological and Fermentative Properties of Baker's Yeast Starter Used in Breadmaking

This study assessed the levels of microbial contaminants in liquid, compressed and dry commercial baker's yeasts used as starters in breadmaking. Eumycetes, Enterobacteriaceae, total and fecal coliforms, Bacillus spp., and lactic acid bacteria (LAB), in particular enterococci, were quantified. Results obtained in this study highlighted that baker's yeast could represent a potential vehicle of spoilage and undesirable microorganisms into the baking environment, even if these do not influence the leavening activity in the dough, as ascertained by rheofermentometer analysis. Different microbial groups, such as spore‐forming bacteria and moulds, were found in baker's yeast starters. Moreover, different species of LAB, which are considered the main contaminants in large‐scale yeast fermentations, were isolated and identified by Denaturing Gradient Gel Electrophoresis (DGGE) and 16S rDNA sequencing. The most recurrent species were Lactobacillus plantarum, Enterococcus faecalis, and Enterococcus durans, isolated from both compressed and dry starters, whereas strains belonging to Leuconostoc and Pediococcus genera were found only in dry ones. Nested‐Polymerase Chain Reaction (Nested‐PCR) and Randomly Amplified Polymorphic DNA–PCR (RAPD‐PCR) were also used to highlight the biodiversity of the different commercial yeast strains, and to ascertain the culture purity.     

Microbial dynamics during aerobic deterioration of silages

Factors affecting microbial dynamics during aerobic deterioration of silages were evaluated in laboratory, pilot-scale and full-scale experiments. Yeasts usually caused the initial deterioration but in some samples with fairly good storage stability (>10 days) the activity was associated with the growth of moulds and bacteria. At a later stage, and especially at higher temperatures (>40°C), the activity was caused by bacilli. The increase in pH as a result of lactate metabolism permitted the growth of Enterobacteria. Evaluation of storage stability in samples from different levels in a bunker silo indicated low stability in surface samples and fairly good stability in samples from 160cm depth. The surface samples contained higher numbers (100–1000 times) of yeasts but the pH levels were similar. The establishment of yeasts during storage is probably due to diffusion of oxygen by leakage through the plastic cover. Compared with a plastic cover (0.1mm polythene), a rubber seal improved storage stability in laboratory silage (pH4.0) inoculated with lactic acid bacteria and infected with Candida albicans. An increase in acid content and a reduction in pH (3.7) by means of an efficient inoculant did not seem to increase the storage potential under the conditions described above. The content of adenosine triphosphate has been used as a measure of microbial activity during aerobic deterioration of silages. The main activity was concentrated at the surface (0–5cm). At 20°C, the activity was about ten times higher at the surface than at a depth of 30cm; above 30°C it was about 100 times higher.     

Evaluation of NaCl,pH, and lactic acid on the growth of Shiga toxin-producing Escherichia coli in a liquid Cheddar cheese extract

A Cheddar cheese model system, Cheddar cheese extract, was used to examine how different levels of known microbial hurdles (NaCl, pH, and lactic acid) in Cheddar cheese contribute to inhibition of bacterial pathogens. This knowledge is critical to evaluate the safety of Cheddar varieties with altered compositions. The range of levels used covered the lowest and highest level of these factors present in low-sodium, low-fat, and traditional Cheddar cheeses. Four pathogens were examined in this model system at 11°C for 6 wk, with the lowest levels of these inhibitory factors that would be encountered in these products. The 4 pathogens examined were Salmonella enterica, Staphylococcus aureus, Listeria monocytogenes, and Shiga toxin-producing Escherichia coli (STEC). None of these organisms were capable of growth under these conditions. The STEC exhibited the highest survival and hence was used to examine which of these inhibitory factors (NaCl, pH, and lactic acid) was primarily responsible for the observed inhibition. The STEC survival was examined in Cheddar cheese extract varying in NaCl (1.2 vs. 4.8%), lactic acid (2.7 vs. 4.3%), and pH (4.8 vs. 5.3) at 11°C for 6 wk. The microbial hurdle found to have the greatest effect on STEC survival was pH. The interactions between pH and levels of protonated lactic acid and anionic lactic acid with STEC survival was also evaluated; only the concentration of protonated lactic acid was determined to have a significant effect on STEC survival. These results indicate that, of the pathogens examined, STEC is of the greatest concern in Cheddar varieties with altered compositions and that pH is the microbial hurdle primarily responsible for controlling STEC in these products.     

Guideline for proper usage of time temperature integrator (TTI) avoiding underestimation of food deterioration in terms of temperature dependency: A case with a microbial TTI and milk

Time-temperature integrators (TTIs) can be used to predict food deterioration. However, underestimation of the magnitude of deterioration is not desirable. This study aims to establish guidelines in terms of temperature dependency (Arrhenius activation energy, Ea) to avoid such underestimation by proper use of TTIs. A case study was executed with a microbial TTI and milk. The Ea of the TTI color change was 106 kJ/mol and those of milk deterioration factors aerobic mesophilic bacteria count, lactic acid bacteria count, ln lactic acid %, and pH were 101, 107, 122, and 145 kJ/mol, respectively. The deterioration factors with values of Ea larger than that of TTI, ln lactic acid %, LAB, and pH, were found to be underestimated as compared to their actual levels by prediction from TTI color change, leading to potential consumption of deteriorated milk.     

Survival of Escherichia coli O157:H7 in cucumber fermentation brines

Abstract: Bacterial pathogens have been reported on fresh cucumbers and other vegetables used for commercial fermentation. The Food and Drug Administration currently has a 5‐log reduction standard for E. coli O157:H7 and other vegetative pathogens in acidified pickle products. For fermented vegetables, which are acid foods, there is little data documenting the conditions needed to kill acid resistant pathogens. To address this knowledge gap, we obtained 10 different cucumber fermentation brines at different stages of fermentation from 5 domestic commercial plants. Cucumber brines were used to represent vegetable fermentations because cabbage and other vegetables may have inhibitory compounds that may affect survival. The 5‐log reduction times for E. coli O157:H7 strains in the commercial brines were found to be positively correlated with brine pH, and ranged from 3 to 24 d for pH values of 3.2 to 4.6, respectively. In a laboratory cucumber juice medium that had been previously fermented with Lactobacillus plantarum or Leuconostoc mesenteroides (pH 3.9), a 5‐log reduction was achieved within 1 to 16 d depending on pH, acid concentration, and temperature. During competitive growth at 30 °C in the presence of L. plantarum or L. mesenteroides in cucumber juice, E. coli O157:H7 cell numbers were reduced to below the level of detection within 2 to 3 d. These data may be used to aid manufacturers of fermented vegetable products determine safe production practices based on fermentation pH and temperature. Practical Application: Disease causing strains of the bacterium E. coli may be present on fresh vegetables. Our investigation determined the time needed to kill E. coli in cucumber fermentation brines and how E. coli strains are killed in competition with naturally present lactic acid bacteria. Our results showed how brine pH and other brine conditions affected the killing of E. coli strains. These data can be used by producers of fermented vegetable products to help assure consumer safety.     

Complete Heterolactic Acid Fermentation of Green Beans by Lactobacillus cellobiosis

Only Lactobacillus cellobiosus, among eight strains of heterofermentative lactic acid bacteria, removed all fermentable sugars from green beans. Proper blanching of the beans was required to prevent growth by natural lactic acid bacteria. An inoculum of 10 CFU/ml Lactobacillus plantarum and 10⁶ CFU/ml L. cellobiosus resulted in the formation of twice as much lactic acid as inoculation with L. cellobiosus alone. A maximum of 3.74% sugar was metabolized by L. cellobiosus in bean juice containing 2.5% NaCI and 0.08% acetic acid. Fructose was nearly quantitatively reduced to mannitol with a concomitant accumulation of acetic acid. Ethanol was not observed until most of the fructose was metabolized. The L. cellobiosus-fermented beans had a more mild acid flavor than beans fermented with L plantarum.     

Silage fermentation of fish or fish waste products with lactic acid bacteria

Silage fermentation of minced fish and fish offal after inoculation with cereals prefermented with Pediococcus acidilactici and Lactobacillus plantarum initiates a rapid fall in pH to below 4.5 within 30 h, and the content of competing gram-negative fermenters and fish pathogens, such as Vibrio anguillarum and Aeromonas salmonicida, is eliminated. The addition of 0.1% sorbic acid inhibits the growth of yeasts during the initial fermentation period and during storage but does not affect the lactic acid fermentation. Degradation of nitrogen components proceeds during storage and is manifested as an increase in volatile basic nitrogen compounds, amino acids and peptides. These substances increase the pH and/or force the bacteria to produce more acid. The rate of production of these basic substances is mainly temperature-dependent and cannot be attributed to microbial activity. The proteolytic activity is mainly caused by tissue proteases (e.g., cathepsins) and, to a lower degree, by gut proteases. It is doubtful whether fish fermentation can be utilised on an industrial scale without improving the technique. Such improvements consist of the selection and use of psychotrophic lactic acid fermenters and commercially acceptable inhibitors of proteolytic activity and yeast growth.