Stability study of fortified low-fat spreads with preservatives

Physicochemical variations in products are known to occur depending on storage conditions. This study examined the effects of storage time on the physicochemical, sensory, rheological, and microbiological properties of fortified low-fat spreads. Fortified spreads containing potassium sorbate (PS) (0.05% and 0.1%) or microgard 100 (MG) (0.5% and 1%) as preservatives and a control spread (CS) were packed in presterilized airtight polyethylene jars and their shelf lives were investigated by storage at 5 ± 1 °C for 90 days. Based on the physicochemical properties, the addition of preservatives inhibited the formation of free fatty acids and thiobarbituric acid and influenced the pH and acidity. The emulsion stability of the preserved samples was greater than that of the CS after 14 days. As storage progressed, the sensory and rheological properties of the CS deteriorated continuously, whereas significantly smaller changes were observed for the samples containing 0.1% PS and 1% MG. The surface growth of yeasts and molds was the main cause of spoilage, particularly in the CS. For all the samples, the standard plate counts and the yeast and mold counts increased during storage. In contrast, the coliform counts were zero, indicating that the samples were manufactured and stored under hygienic conditions. The samples containing lower levels of preservatives (0.05% PS and 0.5% MG) were acceptable for 70 and 77 days as compared to 49 days for the CS. Notably, the addition of 0.1% PS and 1% MG extended the shelf life to 91 days.

Storage related changes in ghee-based low-fat spread

In order to assess the shelf life of a low fat spread (LFS) based on ghee, the product with (PS) and without (CS) added 0.05 % (w/w) preservative potassium sorbate and packaged in 200 g polystyrene tubs was stored at 5 °C and evaluated for changes in sensory, physico-chemical and microbiological properties. On the basis of flavour score, the PS spread could be stored for 10 weeks without appreciable loss in quality as against the CS spread which could be stored only for 5 weeks. From the point of view of spreadability, body and texture and colour, the CS product was acceptable even after 11 weeks of storage. Use of preservative had an inhibitory effect on the development of free fatty acids (FFA) and thiobarbituric acid (TBA) reactive substances. While both the products showed an increasing tendency to whey off during storage, CS wheyed off more than PS. The two spreads showed similar oiling off, which increased slightly during the storage. Microbiologically, the ghee-based low fat spreads with and without preservative was stable for 9 and 3 weeks, respectively, from the view point of yeast and mould growth; but the preservative had little effect on the total viable count. Coliforms were absent in all the samples in fresh and during storage.

Viability of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes in yellow fat spreads as affected by storage temperature

A study was conducted to characterize the survival and inactivation kinetics of a five-serotype mixture of Salmonella (6.23 to 6.55 log10 CFU per 3.5-ml or 4-g sample), a five-strain mixture of Escherichia coli O157:H7 (5.36 to 6.14 log10 CFU per 3.5-ml or 4-g sample), and a six-strain mixture of Listeria monocytogenes (5.91 to 6.18 log10 CFU per 3.5-ml or 4-g sample) inoculated into seven yellow fat spreads (one margarine, one butter-margarine blend, and five dairy and nondairy spreads and toppings) after formulation and processing and stored at 4.4, 10, and 21 degrees C for up to 94 days. Neither Salmonella nor E. coil O157:H7 grew in any of the test products. The time required for the elimination of each pathogen depended on the product and the storage temperature. Death was more rapid at 21 degrees C than at 4.4 or 10 degrees C. Depending on the product, the time required for the elimination of viable cells at 21 degrees C ranged from 5 to 7 days to >94 days for Salmonella, from 3 to 5 days to 28 to 42 days for E. coli O157:H7, and from 10 to 14 days to >94 days for L. monocytogenes. Death was most rapid in a water-continuous spray product (pH 3.66, 4.12% salt) and least rapid in a butter-margarine blend (pH 6.66, 1.88% salt). E. coli O157:H7 died more rapidly than did Salmonella or L. monocytogenes regardless of storage temperature. Salmonella survived longer in high-fat (> or = 61%) products than in products with lower fat contents. The inhibition of growth is attributed to factors such as acidic pH, salt content, the presence of preservatives, emulsion characteristics, and nutrient deprivation. L. monocytogenes did not grow in six of the test products, but its population increased between 42 and 63 days in a butter-margarine blend stored at 10 degrees C and between 3 and 7 days when the blend was stored at 21 degrees C. On the basis of the experimental parameters examined in this study, traditional margarine and spreads not containing butter are not "potentially hazardous foods" in that they do not support the growth of Salmonella, E. coli O157:H7, or L. monocytogenes.