Patent: 4,419,370

Summary for Patent: 4,419,370

Title:	Fish canning process
Abstract:	An improvement in a fish canning process comprising applying to a cut surface of the fish a proteolytic enzyme. There is a marked function in curd formation as a result. The oil color is also improved. The process is of particular interest in salmon canning.
Inventor(s):	Yamamoto; Masanobu (North Vancouver, CA)
Assignee:	B. C. Research Council (Vancouver, CA)
Application Number:	06/326,357
Patent Claims:	see list of patent claims

United States Patent 4,419,370: Fish Canning With Proteolytic Enzyme Pretreatment to Reduce Surface Curd Formation

US Patent 4,419,370 claims a fish canning method that combines (i) conventional canning steps (edible separation, salting, lidding, vacuum, sealing, and heating to cook), with (ii) a narrowly parameterized proteolytic-enzyme treatment applied to the fish prior to the cooking step to reduce “curd formation on the surface of the cooked fish.”

What does the patent actually claim (core technical limitation)?

The core claim (claim 1) is not a general “enzyme tenderization” concept. It is a process definition with strict quantitative enzyme dosing tied to an assay-based activity framework and a timed application window.

Claim 1: Process + enzymatic dosing expressed through activity math

Claim 1 requires:

1) Fish canning process steps

• Separate edible and inedible parts of the fish
• Place edible parts in a container
• Add salt to each container
• Apply lid, form vacuum, seal lid
• Heat to cook fish

2) Enzyme pretreatment before cooking

• Apply proteolytic enzyme to the fish in the container at 2 to 40 mg per 1/2 lb fish
• Enzyme must have proteolytic activity defined by an assay standardization tied to Arnon (1970) and specifically constrained to:
  • proteolytic activity corresponding to 0.5 to 3.0 “as related to the increase brought about per milligram of protein in optical absorbency at 280 nm” by TCA-soluble casein digestion products (per Arnon, 1970)
• Dose must be set so that total proteolytic activity satisfies:
  • (specific activity) × (milligrams of protein) is in 1 to 38 optical absorbency units
• Pretreatment time before cooking:
  • 5 to 90 minutes

3) Functional result

• “curd formation on the surface of the cooked fish is reduced”

Claims 2 to 10 then narrow fish species (salmon species list; steelhead trout). Claims 11 to 16 attach specific mg-per-1/2-lb ranges for papaya latex water extract on particular salmon types. Claim 17 provides multiple alternative enzyme types and their dosage ranges for sockeye salmon.

Dependent claims: enzyme source and species-specific dosing

Key dependent claim structures:

• Claim 3: papaya latex-derived enzyme as a water extract
• Claim 4: enzyme may be one of: pancreatic protease, papainase (spelled “papainaise”), trypsin, ficin, bromelain, prolase, chymopapain, pepsin
• Claims 2, 5-8, 10: specify salmon species (sockeye, pink, chum, chinook, coho)
• Claims 11-16: specify mg/1/2 lb ranges for papaya latex water extract by species
• Claim 17: lists multiple specific proteases and dosage alternatives on sockeye salmon cut surface

How broad or narrow is the claim scope in practice?

Breadth comes from “proteolytic enzyme” plurality, but the activity equation and Arnon-defined activity narrow execution

Claim 1 uses broad language (“a proteolytic enzyme having proteolytic activity of 0.5 to 3.0 as related to…”), and allows many proteases in dependent claims. But the claim also requires:

• dosing in mg per 1/2 lb in a specific range
• compliance with a calculated activity constraint expressed as an “optical absorbency units” range (1 to 38)
• pretreatment time (5 to 90 minutes)
• adherence to assay-defined “specific activity” and standardized conditions “according to Arnon, 1970”

That combination turns “enzyme pretreatment” into a highly assay-dependent process. A competitor cannot simply choose any protease and apply any dose; they must match the claim’s activity window under the same assay framework and ensure the calculated total activity lands within the claimed optical absorbency range.

Narrowness comes from the functional target tied to specific processing and timing

The functional statement (“curd formation on the surface… is reduced”) can be used to argue infringement or noninfringement depending on measured outcome. But the claim does not recite a measurable endpoint threshold; it sets the enzyme parameters and timing. This makes the claim both:

• technology-directional (reduce surface curd)
• parameter-constrained (activity, dose, time)

A process could comply with parameters yet still fail the functional result, but the claim is drafted to couple parameter selection with the result.

Dependent claims narrow further, especially via papaya latex water extract

If a product uses papaya-derived extract, the dependent claims become relevant. If it uses non-papaya extracts or recombinant enzymes, only claim 1 and claim 4 (enzyme list) are potentially available, but the assay math still applies.

Claim-by-claim breakdown for infringement risk mapping

Fish species coverage

• Claim 2: salmon (general)
• Claims 5-8: salmon species
  • sockeye
  • pink
  • chum
  • chinook
• Claim 10: coho
• Claim 9: steelhead trout
• Claims 11-16 correspond to the species list above with papaya latex water extract dosing ranges.

Enzyme source and enzyme set

• Claim 3: natural papaya latex enzyme applied as water extract

• Claim 4: enzyme can be one of:

  • pancreatic protease
  • papainaise (papainase)
  • trypsin
  • ficin
  • bromelain
  • prolase
  • chymopapain
  • pepsin

• Claim 17 specifies alternative proteases and their dosage ranges for sockeye salmon cut surfaces:

  • trypsin: 6 to 12 mg per 1/2 lb
  • ficin: 7 to 14 mg per 1/2 lb
  • bromelain: 30 mg per 1/2 lb
  • proteinase: 14 mg per 1/2 lb
  • prolase: 4.5 mg per 1/2 lb
  • chymopapain: 11.5 to 23 mg per 1/2 lb
  • pepsin: 20 mg per 1/2 lb

Time-at-room-temperature window (5 to 90 minutes)

Pretreatment is required “for a time in the range 5 to 90 minutes prior to the cooking step.” Any shift outside this window would be designed to avoid claim 1.

Key assay anchors

• Arnon (1970), Methods of Enzymology, Vol. XIX 226 is used as the standard for the assay definition tied to:
  • optical absorbency at 280 nm after trichloroacetic acid-soluble digestion products of casein
• The claim imposes a proteolytic activity band (0.5 to 3.0) plus a computed total activity band (1 to 38 optical absorbency units).

This is where non-infringement design effort typically focuses: match the formulation but alter the measured assay characteristics (different protein content, different specific activity, different preparation purity, different extraction conditions) to move the product outside the defined activity band.

Critical analysis: what are the likely weak points in enforceability?

1) Reliance on assay method identity makes both infringement and validity evaluation technical

The claim is effectively anchored to a third-party assay description (Arnon, 1970). If a challenger can show that the assay standards are not the same in the accused process (different substrates, different conditions, different measurement approach), the “0.5 to 3.0” and “1 to 38” constraints can become difficult to prove or match.

From an infringement standpoint, proof likely depends on:

• documenting protease specific activity under the Arnon protocol
• converting the applied enzyme preparation into “milligrams of protein” used for the activity calculation
• showing that the calculated “total proteolytic activity” lands within the asserted window

2) “Curd formation reduced” is functional and could be attacked as non-limiting or as not clearly tied to parameters

Some jurisdictions treat functional language as limiting only if tied to structure or if it provides clear boundaries. Here, the functional limitation is linked to the process steps and parameters, which tends to support limiting effect. Still, “reduced curd formation” lacks a numeric threshold in the claim text, which creates an evidentiary gap: if curd reduction is not consistently observed across the claimed parameter range, defendants can contest whether the functional result is actually met.

3) The claim might be vulnerable to prior art on enzyme pretreatment of fish for texture/processing

A broad literature and industrial practice exists around proteases in meat and fish processing. The patent’s novelty argument would likely depend on:

• specifically applying protease to reduce surface curd formation during canning
• specifying assay-defined proteolytic activity ranges
• specifying pretreatment duration windows
• providing species- and dose-specific ranges for salmon varieties
• using natural papaya latex water extract as a defined enzyme source

If earlier patents or publications disclosed protease addition before cooking/canning to prevent curd-like defects, the remaining differentiator would be the assay-based activity math and the specific dosing/time ranges.

4) Dependent claims create potential “design-around-by-chemistry” paths

Because dependent claims specify papaya latex water extract, an alternative enzyme source may avoid those narrower claims. However, avoiding dependent claims does not avoid claim 1 if the process still satisfies its enzyme activity, dose, and timing constraints.

5) Claim 1 has “in the container” language but later dependent claims focus on “cut surface”

Claim 1 says applying to fish “in the container.” Claims 11-16 and 17 say applying to a “cut surface.” This could create interpretive scope issues:

• If a competitor applies enzyme indirectly (e.g., brine-mediated distribution rather than direct cut surface contact) they might argue the dependent language is not met.
• But claim 1 may still capture the process if application “in the container” occurs in a way that satisfies the core enzyme dosing and timing requirements.

Where the landscape is likely concentrated (and why that matters for freedom-to-operate)

Without enumerating a full worldwide family, the practical “landscape pressure points” for US 4,419,370 are predictable based on the claim structure:

1) Fish canning with pre-cooking enzyme treatment

• Most likely prior art clusters in:
  • preventing protein defects during heat processing
  • improving texture or reducing coagulation-related surface issues

2) Protease activity calibration using optical methods

• The patent’s activity definition relies on an Arnon-type assay framework.
• Competitors and prior art that describe protease units via different metrics (e.g., casein digestion in alternative assay formats) may not fall neatly into the claimed activity bands.

3) Papaya latex derived proteases

• Papain-based processing is historically described across food applications.
• The patent’s novelty claim likely rests on a defined use pattern (canning + curd reduction) plus assay-defined dosing parameters rather than on papaya latex alone.

4) Species-specific salmon dosing ranges

• These dependent claims suggest either experimental optimization or industrial tailoring.
• That also means prior art must cover not just the idea of enzyme pretreatment, but the particular dose/time bands and species-specific selections to anticipate all elements.

Patent value assessment: what parts are commercially defensible?

Most defensible elements

• The combination of:
  • canning process steps including vacuum sealing and cooking
  • proteolytic enzyme dosing parameterized by Arnon-aligned activity and total optical absorbency units
  • a defined pretreatment time window
  • target outcome: reduced surface curd formation

Least defensible elements (typical attack surface)

• Broad “proteolytic enzyme” framing without showing unique chemistry beyond dosing/time/activity windows
• Functional outcome without numeric threshold
• Potential anticipation by earlier protease pretreatment for heat-coagulation defects, if those references include equivalent activity ranges and timing

Key takeaways for R&D and licensing decisions

• US 4,419,370 is best treated as a parameter-locked process patent, not a general enzyme-in-fish concept. The enzyme must fit the claim’s Arnon 1970 assay-derived activity framework and the computed 1 to 38 optical absorbency units total activity constraint.
• Enforceability will hinge on assay correspondence: proving that the accused enzyme preparation’s specific activity and applied protein amount, when multiplied, produces the claimed optical absorbency unit band, and that treatment occurs 5 to 90 minutes before cooking.
• Dependent claims add species and papaya latex water extract specificity, enabling narrower infringement theories but also creating potential design-around-by-enzyme-source strategies.
• The strongest commercial defense is the canning + pretreatment + curd reduction operational window; the weakest is any effort to stretch the claim to processes that alter distribution (cut-surface vs bulk), enzyme prep, or assay-based specific activity outside the stated bands.

FAQs

How does the patent define enzyme potency for infringement analysis?

It defines potency through an Arnon (1970) casein/TCA optical method at 280 nm, with constraints on proteolytic activity (0.5 to 3.0) and a calculated “total proteolytic activity” of 1 to 38 optical absorbency units from (specific activity) × (milligrams of protein).

Does the patent require using papaya latex?

No. Papaya latex water extract is required for dependent claim coverage (claim 3 and claims 11-16). Claim 1 and claim 4 can cover other proteases, as long as activity, dose, and timing constraints are met.

What is the pretreatment timing window?

Claim 1 requires 5 to 90 minutes prior to the cooking step.

What salmon species are explicitly covered?

Sockeye, pink, chum, chinook, and coho are covered via dependent claims, and steelhead trout is covered in claim 9.

What enzyme options are explicitly listed?

Claim 4 lists pancreatic protease, papainaise (papainase), trypsin, ficin, bromelain, prolase, chymopapain, and pepsin; claim 17 further provides sockeye cut-surface dose ranges for trypsin, ficin, bromelain, proteinase, prolase, chymopapain, and pepsin.

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References

[1] US Patent 4,419,370. (197? ). In a fish canning process comprising... (Claim text as provided).

Details for Patent 4,419,370

Applicant	Tradename	Biologic Ingredient	Dosage Form	BLA	Approval Date	Patent No.	Expiredate
Discure Medical, Llc	CHYMODIACTIN	chymopapain	For Injection	018663	November 10, 1982		2001-12-01
Discure Medical, Llc	CHYMODIACTIN	chymopapain	For Injection	018663	August 21, 1984		2001-12-01