Replace thermal sterilization with a combination of selected hurdles.

Consumer demands for high-quality foods are leading to significant modifications in processing technologies. Applying nonthermal treatments and a combination of different hurdle technologies is one way to address these demands.

Minimal or less severe thermal treatments enable foods to better retain heat-sensitive components. These types of treatments also reduce energy consumption. Scientists at Agriculture Canada offer the results of experimental tests using a combination of four selected hurdles: acidification using glucono-delta-lactone (GDL); nisin; irradiation; and thermal pasteurization. The investigators applied these treatments to two foods: chicken broth (bouillon) and Alfredo milk-based pasta sauce.

To verify their research, the scientists used sensory evaluation, accelerated shelf life testing at 35 C and energy consumption as the main evaluation criteria. Their results suggest that single sterilization treatments--the use of individual hurdles--require very high treatment levels, such as strong acidification to pH less than 3.5, high doses of nisin greater than 2 kIU per g, high doses of irradiation greater than 10 kGy and high temperatures of more than 121C.

  In tests, 30 untrained sensory panelists rejected products that were
  highly acidified and which had received high doses of irradiation.
  The relatively high cost of nisin reduced the practical application of
  this treatment to low concentrations.

To overcome these obstacles, the researchers tested several combinations of GDL and nisin at low concentrations. They used low doses of irradiation and pasteurization instead of thermal sterilization. They found the best treatments for both foods to be a combination of: acidification to pH 5.5; a concentration of nisin at 1000 IU per g: irradiation to 2 kGy: and pasteurization at 85 C. By using this approach, about 30% energy savings can be achieved, compared with traditional thermal treatments, while still maintaining the microbial safety of the product.

Further information. Michele Marcotte, Agriculture Canada, Food R and D Center, 3600 Casavant Blvd. West, Saint-Hyacinthe, Quebec Canada J2S 8E3; phone: [phone]; fax: [phone]; email: [e-mail].