Last Update: 9 Dec 2021.
5.6 Curing procedures: Traditionally cured Wiltshire bacon
Bacon & Gammon / Curing
5.6.1 Pork raw material intended for Wiltshire curing shall be either cured on the side, as primal cut, or as individually butchered muscles. The use of ham hock incorporating primary and/or secondary hock muscle) may be used.
5.6.2 The injection and cover brine shall only contain salt, (NaCI) sodium or potassium nitrite and/or sodium or potassium nitrate.
5.6.3 Injection may be carried out manually or by multi-needle injection.
5.6.4 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 and temperature), and the 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.
5.6.5 Due to yield loss, the quantity of live cover brine will deplete over time. Therefore, a standard operating procedure shall be in place for the process to “top-up” an existing live cover brine or, in extreme circumstances, the creation of a new batch of live cover brine.Where a “top-up” brine is used this shall not exceed 25% of the mother batch of live cover brine.
5.6.6 use of a starter culture in the production of Wiltshire bacon shall be restricted to the creation of a fresh batch of cover brine after the original has been lost or has soured.
5.6.7 In order for the live cover brine to mature and stabilise the fresh batch 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 Bacon and Gammon (Wiltshire).
5.6.8 Live cover brines not in regular use shall be regularly aerated and monitored (d) to maintain their condition
5.6.9 Records shall be maintained for live cover brine composition. A recorded log of cover brine history, adjustment and “top-up” shall be maintained to demonstrate composition and provenance.
5.6.10 Pork shall be fully immersed in the live cover brine for a minimum period of 3 days (72hours).
5.6.11 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 4 days and to a clearly specified maximum time that shall be validated using shelf life and food safety analysis.
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 should 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 5.6 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 Bacon, should be clearly described as “Wiltshire-Style” (or similar) within the legal name of the product.
The function of the starter culture is to ensure that the right microbiological flora is present 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 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
There will be occasions when existing cover brines will need to be replenished by the addition of a top-up cover brine – this should be an occasional practice rather than routine. weekly. It is expected that the manufacturer should know the quantity (in litres) of live cover brine they have on stock, so it should be a simple calculation to work out the 25%. Details of the opening stock, closing stock, and top up additions would need to be documented. “this should be an occasional practice rather than routine e.g. weekly, not daily.”
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 takes 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.
Wiltshire-cured sides and cuts are frequently stored in an unprotected form Excess surface brine drains off (the use of hooks, racks, or slatted tray are acceptable as long as free drainage can be demonstrated) and the lean and fat become firmer in texture and noticeably drier. These changes are due to 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