PRODUCTION OF PROBIOTIC LOW-CALORIE SOUR CREAM

The production of probiotic low calorie sour cream was aimed to experiment in relation to its compositional, bacteriological, biochemical, rheological and organo-leptic properties along the cold storage period of the product. Cream based on 36% total solids (TS) and 30 % fat was made using the obtained fresh cream (54 % TS and 50 % fat) and liquid skimmed milk (9 % TS).To produce low-calorie sour cream, fat content was lowered to 20 and 10 % depending on the addition of Sim-plesse100® to mimic milk fat on the basic of 0.1% fat mimetic is instead of 1.0% fat. Dried whey protein concentrate (DWPC, 95 % TS) was used as bulking agent to overcome the loss occurred in the TS content due to the reduction in the fat content. Thereafter, all creams were homogenized at 55-60°C and further heat treated to 74°C for 30 sec. followed by rapidly cooling to the appropriate temperatures. Then creams were inoculated with 2% freshly prepared bacterial starter culture and incu-bated at 30 or 37 °C, to reach pH value about 4.6, for cream cultured with R-704 or ABT-2 type starter culture, respectively. The results indicated that, the proportional fat replacement of cream led to gradual increase in the protein, carbohydrate and ash contents, and decreased the caloric value. There are a backward relationship between the bacterial population and the fat content of the sour cream. Where, in the product cultured with ABT-2 type, Lactobacillus acidophilus grew and predominated in all other accompanying strains overlooking either the fat content or the cold storage pe-riod (CSP). Streptococcus thermophilus populated the 2nd predominance order fol-lowed by Bifidobacterium sp., which tended to proximate and preceded, actually, Str. thermophilus by prolonging the CSP of the lowest fat-content cream (10%). The increase rate of the bacterial count continued until 3rd weak for Lb. acidophilus and to 1st weak for Bifidobacterium sp.. Thereafter, gradual decreases were occurred. However, Str. thermophilus began to decrease from the 1st day of CSP. Although the count of bacterial type R-704 was always higher, it behaved a trend similar to that of Bifidobacterium sp. toward the CSP. Sour cream of ABT-2 type contained higher ti-tratable acidity (TA) % as well as lower pH, acetaldehyde (AC) and diacetyl (DA) values than that cultured with R-704 type. Along CSP of sour cream the increment in AC, DA and TA contents continued, in order, until the 7th , 14th and the end of the
Fayed; Gehan Hussein and Azza Farahat
Arab Univ. J. Agric. Sci., 14(2), 2006
experimental period. As the protein content raised at the expanse of the fat content via adding DWPC, which was in the denatured form, the firmness, consistency coef-ficient, and yield stress of sour cream increased, especially when ABT-2 type was used and the CSP progressed. Furthermore, ABT-2 sour cream was sensory distin-guished with, nearly, similar appearance as will as better flavour and consistency ra-ther than that of R-704. The fat reduction to 20 % did not influence the overall sen-sory quality, while that of 10% fat attained panel score averaged 93.5 % of the con-trol when ABT-2 type was used. As a conclusion, it is successfully possible to pro-duce probiotic low calorie sour cream with excellent sensory attributes using Sim-plesse100® as fat mimetic and bacterial type ABT-2 as starter culture.