Shelf Life and Preservation

i.Paneer

The relatively short shelf life of paneer is a major handicap in the commercial adoption of paneer manufacture. The shelf life of paneer is reported to be only 6 days under refrigeration though its freshness is lost within 3 days. At room temperature paneer does not keep good for more than one day. The heat treatment given to milk is more than enough to destroy all the pathogenic and spoilage microorganisms. Thus it is the contamination either during or post manufacturing which is responsible for this spoilage. Paneer blocks obtained after pressing are immersed in water for cooling.It is during this period that microorganisms establish themselves in the product and proliferate on storage later on. The dipping water is a potent source of contamination and its quality is very important.

The spoilage in paneer occurs due to the surface growth of microorganisms. A greenish yellow slime forms on the surface and the discolouration is accompanied by an off-odour. It is only the surface that gets spoiled early while the interior remains good for a longer time. To curb the surface growth of microorganisms and thereby increase the shelf-life of paneer, the following practices can be successfully adopted.

Chilling: Rapid chilling of paneer is necessary to arrest the growth of microorganisms.Normally the producers do not see to it that the temperature of paneer has been brought down sufficiently (5-10oC) and it usually remains in the range of 20-30oC at the time of packaging. If such paneer is transferred to a refrigerator or cold store, it takes quite some time to cool down to the desired temperature. Microorganisms get fully established by that time and cause spoilage of the product. The bacteriological quality of chilled water should also be very high. It is essential that pasteurized chilled water should be used for cooling of paneer blocks.

Brining: Paneer dipped in 5 percent brine solution lasts for nearly 20 days as against control that is spoiled after 6 days of storage at 8-10oC. The sensory attributes are rated higher for salted samples. Since paneer is mostly salted and spiced before consumption, the salting at the time of dipping can be advantageously used in extending the shelf life of paneer. For preparation of brine salt should be dissolved in pasteurized water.

Use of chemical preservatives: A shelf life of 32 days under refrigeration can be achieved when paneer is treated with a combination of delvocid and hydrogen peroxide. Shelf life of 40 days using benzoic acid (1200 ppm) under refrigeration conditions and 20 days at 37oC has been reported. Further, enhanced shelf life of 36 days at room temperature by adding sorbic acid to milk (0.15%) and subsequent wrapping of paneer in sorbic acid coated paper can be achieved.

Freezing: On storage of paneer at sub zero temperature i.e. –13oC and –32oC for 120 days, the flavour and appearance is not affected but its body and texture deteriorates and the product becomes crumbly and fluffy on thawing. Blast freezing has recently been used to enhance the shelf life of paneer. The paneer block is cut into pieces of approx. 1.5 x 1.5 x 1.5 cm size and blast frozen at a temperature below –20oC. The product can be stored under frozen conditions (below –18oC) for more than one year without any deterioration in its quality.

Vacuum packaging: Vacuum packaging of paneer in laminated pouches can help to increase its shelf life to about 30 days at 6±1oC. The body and texture of paneer also improves on vacuum packaging as it becomes more compact and shows better sliceability. Paneer packaged in high film (EVA/ EVA/ PVDC/ EVA) under vacuum and heat treated at 90oC for one minute is reported to have a shelf life of 90 days under refrigeration.

Heat sterilization: Although the refrigerated shelf life improves markedly by the various treatments given to raw paneer, the shelf life at room temperature does not improve noticeably. Heat sterilization of paneer is an effective treatment for improving its shelf life at room temperature. Paneer packed in tins along with water/ brine and sterilized in an autoclave at 15 psi for 15 min lasts for 4 months. The perception of an oxidized flavour renders the product unacceptable afterwards. A slight amount of cooked flavour accompanied by maillard browning, the intensity of which increases slightly during storage, is noticed.

Grass additives: In order to enhance the keeping quality of paneer, the efficacy of four grass additives viz. cardamom, clove, cinnamon and ginger were investigated.The additives were individually added to milk at the time of coagulation. Ginger was added at the of 5, 9 and 11 g per kg milk and cardamom, clove and cinnamon were added at the rates of 1.0, 1.5 and 2.0 g per kg of milk. Paneer samples containing ginger, cardamom, clove and cinnamon each for low, medium and high dose showed shelf life of 32, 36 and 40 days; 23, 32 and 36 days; 24, 28 and 32 days; 23, 28,and 32 days, respectively at refrigerated temperature (5±1oC) while paneer was treated with brine (4.5%) and packed in polyethylene pouch (550 gauge), pre- sterilized with hydrogen peroxide (20% v/v). Clove and Cinnamon treated samples exhibited same shelf life as per their respective dosage. On the basis of sensory evaluation and physico-chemical changes during storage, medium dosage of four spices were found to be most effective and in totality, the treatment of paneer with
medium dose of ginger followed by medium dose of cardamom and clove/ cinnamon,respectively was most effective.

 

ii.Chhana

Chhana is perishable milk product. At ambient temperatures, its quality deteriorates within a day or two. The shelf life of chhana is greatly influenced by the composition of chhana particularly moisture content, storage temperature and nature of packaging material. The average shelf life of chhana from both cow and buffalo milk at 4oC,22oC and 37oC is about 10-12 days, 3-4 days and 2-3 days, respectively. The cow milk and buffalo milk chhana stored in tin cans and cellulose film/ LDPE was found acceptable upto 3 days at 37oC, and 20 days at 4-5oC. The shelf life enhancement of chhana using sodium benzoate, sodium propionate and sugar has also been demonstrated. Under refrigeration, the shelf life is extended to six days.

 

iii. Chhana Based Sweets

The shelf life of chhana based sweets is largely depend on the processing and packaging conditions, method of handling, season and moisture content in the product.Normally sandesh has a very limited shelf life of two to three days. Hard grade has better shelf life than soft grade ones. In summer, the shelf life of hard grade Sandesh is between three to four days while in winter it kept well four to six days. The relatively longer shelf life of this product may be due to low moisture and high sugar contents. Serpak Sandesh is having maximum shelf life of two to three months under refrigeration storage. Serpak is prepared by heating chhana and sugar for a longer duration. Babupak Sandesh deteriorates rapidly and in summer its shelf life is one day. Whereas, Batupak sandesh is having shelf life of two of three days. In winter,the shelf life of Babupak and Batupak sandesh may be extended upto two and five days, respectively.

The shelf life of rasogulla is quite longer as compared to sandesh. Rasogulla is packaged in lacquered tin cans with hot syrup. Sodium metabisulphite is added to maintain white colour to tinned rasogulla. The shelf life of rasogulla with permissible preservatives in tin containers is above three months.