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Hydrogels with different weight percent of $N$-hydroxylethyl acrylamide and $N$-(2-mannosylethyl) acrylamide were prepared, using $N$, $N^{\prime }$-methylenebis (acrylamide) (MBA) (1.0wt.%) and ammonium persulfate (APS) (1.0wt.%) as the crosslinker and initiator, respectively. The successful preparation of hydrogels was confirmed by both inverted vial test and rheological measurements. These hydrogels were grinded into nanogel powders and applied as a bromelain stabilizer against high temperature by measuring the proteolytic activities of bromelain, which increased from 47% to $>$95% under nanogel protection. This indicated that nanogels can be potentially applied as an enzyme stabilizer in food industry.

The potential therapeutic value of bromelain is due to its biochemical and pharmacological properties and hence, it is desired to obtain bromelain in its highest purified form. Crude bromelain extract can be obtained from the fruit of Ananas comosus using ion exchange chromatography. Bromelain thus obtained can be subjected to either spray or freeze drying. The resulting residual activity and the specific activity were compared between the spray and freeze dried powders. Freeze dried bromelain was found to posses the specific activity twice as compared to the spray dried powder. The effect of protective agents and the bulking agents on the retention of activity was studied in both spray as well as freeze drying. The initial results have been encouraging as 90 % of the bromelain recovery was possible.

The paper investigated the activity of bromelain extracted from fresh pineapple juice over three years to figure out the optimal harvest time for bromelain in the Zhanjiang region. The method of statistical analysis had been used for determining the bromelain activity in every month of a year. Meanwhile, the average moisture content and activity of bromelain in were month were linear analysis. The results indicated that November was the best time for bromelain production and processing in a year; the average bromelain activity of November reached 1.089×10⁶ U/g. The outcomes demonstrated that both of temperature and humidity played important roles in bromelain production.