Jam preparation is a preservation technique where
the liquid state of fruit is transformed into a solid state. Citric acid plays
a vital role in maintaining the desired pH of jam which is subsequently
affecting on the microbial stability of the product. The standard ph range of
jam is 2.8-3.3 and titratable acidity affect on the gelation ,flavor and shelf
life of jam. Sugars are very important not only for flavor enhancing,but also
for the formation of sufficiently firm gels by their water binding capacity
.(Zeki Berk,2016) With the combination of sugar component in jam
preparation,water activity is highly affected. When sugar
concentration becomes high,the water activity gets low.thereby,it affects on
microbial stability throughout the storage time.yeast and mold counts are
related with sugar based fruits and here, the counts may be reduced if the
product is made by adding preservatives.With the time,there is a slight
increment of microbial counts in total plate count and yeast and mold counts.
That emphasizes the fact that sugar is not sufficient to suppress the growth of
microbes during storage period.High moisture content within the product may
also be a reason for mould damage. Microbial counts may have decreased even if
the thermal cooking time, total soluble solid content could be increased.
Generally,during jam preparation microorganisms are destroyed within the
product itself as the boiled jam is hot filled into sterilized glass bottles
which are subsequently sealed ,then inverted so that hot jam contacts the lid
surface ,spoilage by microoorganisms will not take place throughout the storage
period.
(FAD/WFP,1970) Eventhough microbial counts gradually increased with time ,they
were below the sls standard maximum limits(standard maximum limit for total
plate count and yeast and mold count should be equal or less than 103
and 102 colony forming units per gram respectively)in all the plates
cultured during the storage period.