Dear Tony-C,
There is no substitute for practical experience IMO (eg see the introductory “exception” to the process section) and I hv very little for milk/yoghurt (now slightly more) . However the material below will hopefully re-energise the yoghurt project a little.
Initially the basic concepts of manufacturing yoghurt seemed attractively simple however the scientific underpinning is IMO quite complex, not to mention the considerable permutations of (large scale) manufacturing techniques possible. I suspect a lot of other posters unfamiliar with this manufacturing area will hv met the same problem hence the limited responses.
Most of the accessible detailed info. on this topic seems to be in textbooks / official/ internal guideline however I can suggest the 2 websites below (repeat of prev.post) for basic stuff. In adddition the attachments previously posted by Inesa are extremely useful. Any other legitimate web sources are welcome to be submitted of course.
http://www.foodscien...ryedu/home.html
http://www.milkfacts...essing Page.htm
I also hv no direct experience of ISO 22000 procedure expectations (as per 7.3.5.2) and I found the ISO text rather ambiguous. Accordingly, I hv interpreted the requirements as a basic outline similar to my experience for traditional
haccp, ie to facilitate understanding of the concepts / manipulations given in the flow diagram.
I hv included some (probably ISO unwanted) pictorial backups / semi-explanations of the phyisicochemical concepts involved in the process to hopefully assist / attract comments from other yoghurt non-practitioners like myself. This has probably at least tripled the basic ISO “length” requirements. To illustrate the degree of “expansion” I hv also included a (very) “stripped-down” example (b04) focussing on the practical content of fig b01 in order to seek opinions from the ISO users / experts here on whether this condensed format is in fact acceptable from an audit point of view (my experience in traditional
haccp plans is that ingeniously short / microscopic font size / tabulated presentations can often be quite acceptable to auditors although less so to myself).
I chose to not include (rightly or wrongly ?) any ISO type “hypothesised” /cross-referenced / procedures / work instructions. (I hv previously encountered differing
HACCP interpretations of the slightly analogous “Process SOP”, eg some people viewed it as a simple manufacturing description, others as a compendium to also contain reference to all the related QA procedures >> mini-encyclopaedia ).
A brief overview of the relationship between this process and likely microbiological safety hazards could hv been included however I thought it would be more logical, if indeed required at all, to position this within the following 7.4 ISO 22000 section. If considered otherwise, can be done.
A few introductory comments regarding already posted thread material -
(a) The existing project flow chart seemed (slightly) mis-matched to the (rare) process descriptions I could find for “Greek” high fat yoghurt (10% apparently beloved in the UK!), particularly regarding “concentration” steps post-fermentation. Accordingly I hv initially simply used data given for more “normal” fat yoghurts, eg 1-3% fat levels. My knowledge deficit unfortunately, text probably easily modified if required.
(b) The terminology “striking” seems to have vanished from modern texts (and usage?), could only find (2) references in older books. I deduce this term is specific to “in-tank” agitation (as compared to heat exchanger based processes [or perhaps combinations thereof?]). There appear to be 2 basic options for cooling after fermentation, ie “in-tank” or “continuous” ( external heat exchanger ). I hv assumed an “in-tank” option in view of the “striking” (and it happens to match my picture!) although in practice, a heat –exchanger looks like a faster choice to me. It also seemed (to me) that in-tank cooling will necessitate further (undesirable?) fluid agitation for a reasonable time to completion, in addition to the planned “striking”, but I could not find any decisive published comments on that.
© For simplicity / lack of data, I hv assumed all the probiotic culture components included in the product specification are addded at same time / location as a traditional “bulk” culture pair of LB/ST and that the operational data typically given for the latter is not significantly changed. There may be significant errors here but my knowledge lacking again, eg hv seen these comments in different works - high pasteurisation temperatures (min.95degC/1hr) are mandatory for some probiotics, levels of starter culture around 10-20% v/v are necessary, probiotic additional components best added after (traditional) fermentation. May simply be that all these variations are (randomly) employed.
(d) Virtually all the model processes I found seemed to use more severe pasteurisation conditions at the prior-to-fermentation step (ie No.21) compared to the project suggested HTST values (I note you inc. some > signs). Conversely, the (very limited) data I found for “pasteurisation” steps Nos.15,16 used milder (thermisation) options. I “compromised” and hv quoted a typical range of options for “21” however no problem to re-specify HTST everywhere if preferred (there may again be a good reason for the lower temp. end which is outside my knowledge base ).
(e) I found a lack of consensus regarding the order of steps 21 and 22 (pasteurisation/homogenation). The reverse order to this presumably has bacteriological advantages however several recent texts did seem to prefer the projects’s existing format, perhaps for high fat items(?) and assuming an “aseptic” homogeniser after pasteurisation. Just curious, AFAIK, no particular flow problem either way.
(f) I added step numbers to yr Part II flow chart (b05). Unfortunately my graphic package is much less capable than yours. Feel free to issue a prettier version as pe PtI. One item ( my No.24A) seemed to be a duplicate (?).
(g) I hv omitted any treatment of the waste disposal elements. Burnout risk. Can be added eventually.
b06a - process description stirred yoghurt.doc 281KB
153 downloads
Rgds / Charles.C
PS I hv no doubt that there are a number of typos in the text. And probably some blunders also. Sorry in advance.
PPS I realise there is no nice list of control measures to match the ISO requested text. It seemed to me that these would logically come from the hazard analysis which we haven't got to yet so i ignored it. I wait for enlightenment. I love ISO.