The offence is punishable under section 272 IPC punishable with Imprisonment of 6 months or 1000 rs fine or both. 

You can defend yourself by providing other packed samples from manufacturer which are also adulterous.

See in such case penalty is imposed and imprisonment is not there most of time so best thing to do is plead guilty before magistrate as per view pay the fine and close the case.

Alternatively if you wish to contest you need to engage an advocate and can further proced with case pleading not guilty .

Depends on what section he charges on you. The punishment will depend on the same.  You can take the same defense that you are not manufacturer

Anyone either by themselves or through any other person on their behalf manufactures or imports for sale, stores, selling or distribution of any food article unsafe for human consumption will be punishable where the contravention 

does not lead to injury  an imprisonment term up to six months and fine up to Rs. 1 Lakh.

results in non-grievous injury  an imprisonment term up to one year and fine up to Rs. 3 Lakh.

results in grievous injury  an imprisonment term up to six years and fine up to Rs. 5 Lakh.

results in death  an imprisonment not less than seven years which could be extended up to life imprisonment and a fine not less than Rs. 10 Lakh.

The FSSAI regulations provide for various punishment to persons who adulter food or food products as under:

• Import, manufacture, storage, sale or distribution of any food article which is adulterated by allowing its quality or purity to fall below the prescribed standard, or is misbranded, or in contravention of any provision of the Act or Rules. The penalty for this offense is a minimum imprisonment of six months that may extend up to 3 years and a minimum fine of Rs 1000.

Your crime is covered u/s 7 r.w. s.16 of PFA Act and rules because you have been found selling adulterated material in their view, as this will go to the criminal court move an application that the material was manufactured by name of the firm and you simply selling the same so the firm concerned be called to reply and be sued,letting you off otherwise they may sentence you min. Six Months and max.03 Years with fine.

Any person who manufactures for sale or stores any article of food for human consumption which is sub-standard, shall be liable to a penalty which may extend to five lakh rupees.

You have not manufactured but due to long storage, article may rot. How long was floor stored at you ?

Forget about the punishment which will be announced later on, before that on receipt of notice you may appear before the authorities concerned and explain your position along with the bills of the wholesale shop you purchased and try to defend yourself, if you are not at fault then you dont have to worry.