Improving Shelf Stability of Peanut Butter and Peanut Butter/Strawberry Jam Tarts

Summary

It is possible to formulate and process a nutritious and convenient to use bakery product suitable as both a breakfast and a snack product. The product is relatively shelf-stable when stored under proper conditions.

Situation

Breakfast is considered the most important meal of the day for many people, especially the young. Health studies have shown that eating breakfast can increase energy and concentration levels, and reduce the risk of diabetes and obesity. The increasing popularity of breakfast has led to an increase in the development of new products which primarily center on convenience. Bakery products have been an important part of a balanced diet for thousands of years. They are convenient, nutritious, easy to package, and shelf stable. Peanut butter and peanut butter/strawberry jam-filled breakfast tarts are one such product developed with the idea of providing a convenient and nutritious food. These tarts contain peanut butter, which is a good source of protein. The development of a peanut butter-filled breakfast tart and its consumer acceptance has been documented. However, the shelf life and packaging (type of package and atmosphere) which would deliver maximum shelf life while maintaining consumer acceptability of this product have not been determined.

Response

In this study we investigated the effect of package type and atmosphere. Specific objectives were to determine: a) the shelf life of peanut butter and peanut butter/ strawberry jam-filled tarts packaged in three types of packages and stored at two conditions of temperature and relative humidity (%RH); b) moisture content, water activity, and pH of the crust and the filling; and c) consumer acceptability of the stored tarts. The tarts were formulated and baked in a conventional oven at 177 C for 10 min; after cooling, they were packaged individually in paper sleeves, and then placed in cardboard pizza boxes. The boxes were stored at two temperature and humidity conditions in three types of packages. The three types of packages were cardboard boxes, cardboard boxes sealed in high barrier bags, and cardboard boxes sealed in high barrier bags flushed with nitrogen. The storage conditions were 22 C/ 50% RH, termed as room temperature storage, and 32 C/ 70% RH, termed as elevated temperature storage. Sample tarts were collected every 3 weeks and analyzed for microbiological, sensory, and physicochemical changes. Tarts filled with peanut butter/strawberry jam had a higher initial moisture content compared to the peanut butter tarts. Moisture from strawberry jam might have migrated to the surrounding crust increasing its moisture content. The crust and the filling of peanut butter tarts stored at room temperature lost moisture with the increase in the length of storage. The moisture content of the crust and the filling during the test period was always associated with the tarts stored at elevated conditions irrespective of the type of package. The highest moisture content was always associated with tarts stored in cardboard boxes. The tarts stored at room temperature conditions lost moisture at a faster rate than the ones stored at elevated conditions in the same packaging. Among the tarts having peanut butter/strawberry jam filling, the tarts stored at room temperature lost more moisture than the ones stored at elevated temperature. At room temperature, the tarts stored in cardboard lost moisture rapidly compared to the ones stored in high barrier bags (air or nitrogen flushed). The loss of moisture from the filling was also considerable. The filling of the tarts stored in cardboard at room temperature lost moisture at a faster rate than the tarts stored in high barrier bags (air or nitrogen flushed). The peanut butter/strawberry jam filling had become very dry by the 9th week of storage and had a rubbery consistency. Migration of moisture affected the water activity, texture, sensory and microbiological profile of the product. The total bacterial counts of the crust and filling at day 0 were 1.47 log10 CFU/g and 2.48 log10 CFU/g, respectively, while the yeast and mold counts of the crust and the filling at this time were 1.76 log10 CFU/g and 3.12 log10 CFU/g. The results of this study showed higher mold counts in tarts stored at high moisture and relative humidity conditions (32C/ 70% RH). The total bacterial counts and yeast and mold counts at the end of 9 weeks of storage were not more than 3.12 log10 CFU/g in all the batches studied, which means that the tarts were safe for human consumption. Sensory analysis of tarts showed reduction in quality with storage time. Tarts rated 5 or higher on the hedonic scale (1= dislike extremely, 9 = like extremely) are considered to be of acceptable quality. The appearance of the peanut butter and peanut butter/ strawberry jam tarts at day 0 was in the range of “like very much” to “like extremely”. With increasing storage time, the appearance ratings for peanut butter/ strawberry jam became lower than the ratings for peanut butter tarts. Similarly, the color rating for peanut butter/ strawberry jam tarts was lower than that for peanut butter tarts at the 9th week of storage. Flavor ratings followed a diminishing trend and became unacceptable at the 9th week of storage for most of the tarts. The texture ratings for the tarts decreased as the length of storage increased. Moisture loss from the tart crust and filling led to the very low ratings. Peanut butter and peanut butter/strawberry jam tarts had an overall acceptability ratings of “like very much” at the start of the study. Some tarts began to lose their overall acceptability as early as the 3rd week of storage. By the 9th week of storage, all tarts with the exception of peanut tart stored at room temperature and packaged in high barrier bag flushed with N2 had overall acceptability ratings of less than 5. Based on the results of this study a follow-up study has been designed utilizing individual foil pouches for packaging the tarts, rather than the high barrier film and bulk packaging employed in the present study.

Impact

It is possible to formulate and process a nutritious and convenient to use bakery product suitable as both a breakfast and a snack product. The product is relatively shelf-stable when stored under proper conditions. However, there is a potential to significantly enhance the shelf-stability of this product by properly selecting a packaging material and packaging environment. The second phase of this study has begun to further address this issue of shelf life and packaging (type of package and atmosphere) which would deliver maximum shelf life while maintaining consumer acceptability of this product.

State Issue

Agribusiness Development/Value Added

Details

• Year: 2006
• Geographic Scope: International
• County: Spalding
• Program Areas:
  • Agriculture & Natural Resources