Last Update: 5 Jan 2022.
6.3 Curing procedures: Category 2 – Traditionally cured Wiltshire ham or ham hock
Ham & Cooked Pork / Injection and curing procedures
6.3.1 Pork Legs intended for Wiltshire curing shall be either cured on the side, part-side, or as individually butchered legs or associated muscles.
6.3.2 Ham Hock (comprising of primary and/or secondary shank as defined within Appendix 1) shall be slow cooked to breakdown the gristles and sinews associated with these cuts.
6.3.3 The injection and cover brine shall only contain salt (NaCI), sodium or potassium nitrite and/or sodium or potassium nitrate.
6.3.4 Injection may be carried out manually or by multi-needle injection.
6.3.5 It is a characteristic feature of Wiltshire curing that the live cover brine shall be re-used continually. Therefore, standard operating procedures, work instructions and records shall be in place that state the compositional targets and tolerances (salt, nitrate, nitrite, pH & temperature), and actions to be taken when these fall outside of stated limits, so that the condition of the live cover brine can be maintained and where necessary corrected. All actions and brine amendments shall be recorded.
6.3.6 A starter culture shall only be used in the conception of the fresh immature live cover brine. At conception, the brine shall be regularly aerated and checked to ensure that the starter culture is active and that the condition of the brine is developing. To facilitate development the immature live cover brine shall be used to cure products for at least two months before it can be used to manufacture product that can be certified as BMPA Quality Assured Ham and Cooked Pork.
6.3.7 Over time the volume of live cover brine will deplete so occasional “top-up” using a freshly prepared brine incorporating a starter culture may occur. The mother brine to which the “top-up” brine has been added can continue to be used on the condition that the “top up” brine shall not exceed 25% of the mother batch of live cover brine.
6.3.8 Live cover brines not in regular use shall be regularly aerated and condition monitored to maintain its condition.
6.3.9 A recorded log of cover brine history, top-ups, and adjustment shall be maintained to demonstrate composition and provenance.
6.3.10 Pork shall be fully immersed in the live cover brine for a minimum period of a 3 days (72hours).
6.3.11 After immersion, and prior to further processing, the cured sides/pork cuts shall be allowed to drain and then matured in air at +2°C to +5°C for a minimum of 96 hours (4days) and to a clearly specified maximum time that shall be validated using shelf life and food safety.
In a Wiltshire-curing system, the objective is to maintain the live cover brine in a stable condition with a predictable and controlled rate of conversion of nitrate to nitrite.
Brines used in different plants vary in their behaviour due to differences in their micro flora and this behaviour must be recognised. Because of their singular nature a unique characteristic is that the live brine is continually re-used. The practice of freshly and routinely preparing the live cover brine by the addition of a starter culture is a modern short cut intended to circumvent the traditional time aged process and is not compliant with the requirements of Clause 6.3 that is specific to the traditional process. To be certified by the charter such products, for the purpose of labelling and differentiation from authentic and traditionally Cured Wiltshire Ham and Ham Hock, should be clearly described as “Wiltshire-Style” (or similar) within the legal name of the product. Such products, depending on the final water content of the finished product would either fall with the definition of a Category 3: Ham with No Added Water (see Clause 6.4) or Category 4: Ham with Added Water (see Clause 6.5).
The function of the starter culture is to ensure that the right microbiological flora is present in order for the live brine to mature to a point where it can be self-maintaining with occasional additions of salt, nitrite and nitrate to maintain its condition. Typical levels of microflora are of a count greater than 106 and are predominantly made up of large concentrations of micrococci and lactobacilli. Once the mature live cover brine has been created the brine can then be re-used without further addition of the starter culture, except for occasional top-up as explained below.
There will be occasions when existing cover brines will need to be replenished by the addition of a top-up cover brine normally created by using a starter culture – this should be an occasional practice rather than routine.
Immersion forms an essential part of the Wiltshire process. In Wiltshire curing, the relative concentrations of the injection and live cover brines result in a net withdrawal of water from the pork during curing because the concentration of salt in the injection brine is considerably less than that of the live cover brine.
The pH of a live cover brine is usually stable and typically falls within a range of 5.0 to 6.9. The pH value may be checked whenever brine is being re-strengthened and live cover brine with pH outside this range may be used if the charter participant can demonstrate that the brine remains stable (different starter cultures can create different pH levels). Occasional peaks outside of the set limits would not be an issue if the charter participant is monitoring the pH trends and take corrective action when non-typical pH profiles emerge. A gradual and persistent rise in the pH value indicates that the brine is becoming unstable and a critical situation will arise if this goes above 6.9, when off-odours will develop. The rise in pH is usually accompanied by an increase in the nitrite level, as a more rapid reduction of nitrate occurs.
Temperature-control plays a vital part in the production of cured pork. In most of the curing systems used commercially the operations are performed at +2°C to +5°C.
Wiltshire-cured legs are frequently stored in an unprotected form. Excess surface brine drains off (the use of hooks, racks, or slatted trays/dolavs are acceptable if free drainage can be demonstrated) and the lean and fat become firmer in texture and noticeably drier. These changes are concerned with the gelling of the water/salt/protein complex formed within the meat during curing and a gradual hardening of the fat as the crystallizing process continues after slaughter.
Examples of records to be reviewed since the last audit shall comprise:
- Live cover brine composition
- Log of cover brine history, adjustments and “top-up” to demonstrate provenance.
- Temperature monitoring
- Shelf life and food safety analysis
- Appropriate work instructions