MICROBIOLOGICAL AND SENSORY CHARACTERISTICS OF A HOME STYLE CONFECTIONARY PRODUCT

PREPARED WITH CREAM CHEESE

DAVID SCHMIDT

Carnation Company 150 Riverview Drive

Jefferson, Wisconsin 53549

and

STEPHEN C. RIDLEY

Depanment of Food Science The University of Wisconsin

River Falls, Wisconsin 54022

Accepted for Publication January 10, 1984

ABSTRACT

A study was undertaken to examine the microbiological and sensory qualities of a home-style confectionary product containing cream cheese. There was a rapid reduction in the numbers of Salmonella and Staphylococcus aureus during theJirst 24 h ajier inoculation. Reduction continued through three weeks of storage at room temperature (20-24 “C) and refrigerator temperature (5-7”C), but not at freezer temperature (- IO’C), where counts remained higher. Sensory analysis showed that the product stored at - 10°C for three weeks compared favorably in flavor and tex- ture with a freshly prepared product and that storage at 20-24°C or 5-7°C resulted in a deterioration of these qualities. f i e water activity of the product was 0.86 and did not change during the three week storage period.

INTRODUCTION

Within the past few years, it has been brought to the attention of these authors that a number of homemakers in Wisconsin and Minnesota are using various recipes for preparing a confectionary product containing Philadelphia style cream cheese. These candies, known locally as “cream cheese mints,” are generally prepared as a specialty item to be served with holiday dinners, wedding receptions, banquets, etc., and as such are often consumed by a large number of people at one time. Because of the popularity of this product, it seems likely that someone will consider produc- tion on a commercial scale. There apparently is considerable interest in producing

Journal of Food Quality 7 (1985) 283-287. All Rights Resewed Vopyright 1985 by Food & Nutrition Press, Inc., Wesfport, Connecticut

283

284 D. SCHMIDT and S. C. RIDLEY

confectionary products with improved nutritional value according to a recent article by Richardson (1980). The use of cheese and other dairy products as ingredients might be a means of achieving this. The possibility of production on a commercial scale raises questions about shelf-life, storage and packaging methods and product safety.

Confectionary foods, because of their high sugar and low moisture contents, do not normally support microbial growth, but Salmonella has been known to survive in candy and to cause illness (Hilker 1976, Just and Strauss 1981). Staphylococcus aureus, which is known to grow at a lower water activity than many other bacteria could also pose a problem with this type of product.

This work was undertaken to determine the best method for storing cream cheese mints and to determine the potential for safety problems related to growth and sur- vival of microbial pathogens, particularly Salmonella and Staphylococcus.

Methods and Materials

Individual, home-style cream cheese mints were prepared by mixing 112 g of Philadelphia Style cream cheese (Kraft) with a hand-held electric mixer. A small amount of water, 8.5 g, was added to aid in obtaining a creamy consistency. Green food coloring, (McCormick and Co., Inc., Baltimore, MD) 0.45 g, and McCor- mick liquid mint flavoring, 0.60 g, were added to give desirable color and flavor. This was followed by thoroughly mixing 455 g of confectionary sugar and then hand- kneading for five min on a flat surface covered with 65 g of confectionary sugar. One-half of each batch prepared was then formed by hand into small balls of about 2 cm in diameter. Each ball was lightly rolled in extra fine granulated sugar and pressed by hand into a rubber mold coated with granulated sugar. Each mint was placed on waxed paper, covered with granulated sugar, and allowed to harden for 24 h prior to storage. It was estimated that approximately 25-30 g of granulated sugar was incorporated into each batch. The individual mints were then stored for three weeks in polypropylene food containers with friction fitted lids at three dif- ferent temperatures, 21-24"C, 5-7 "C, and - 10°C. Following the storage period, each sample was tested for moisture content by drying at 70°C under 61 cm vacuum for 48 h. Sensory evaluation was performed by a panel of 10 students in an undergraduate food analysis class. The students had been given limited training by exposing them to the product once prior to testing. Testing was done in two parts, ranking for preference and evaluation of flavor and textural moistness on a seven point scale, using the following designations: like extremely, like moderately, like slightly, neither like nor dislike, dislike slightly, dislike moderately and dislike ex- tremely. There were four samples per test, the three storage samples and one prepared fresh on the day before the test. Ranked scores were adjusted (Fisher and Yates 1957). All data were analyzed by variance in a randomized complete block design (Steel and Torrie 1960).

CHARACTERISTICS OF CREAM CHEESE MINTS 285

The other half of each batch was stored under identical conditions, but prior to making the individual mints on the mold, the product was inoculated with approx- imately lo6 cells of Staphylococcus aureus and Salmonella typhimurium. Following storage, the inoculated mints were quantitatively tested for recovery of these organisms by standard methods (Speck 1976) for Staphylococcus aureus. The nonselective enrichment procedure was used followed by direct plating on Baird- Parker agar (Speck 1976). For Salmonella, pre-enrichment was done with reconstituted nonfat dry milk followed by enrichment in Selenite Cystine and Tetrathionate broths and plating on Bismuth Sulfite and Brilliant Green agars (Speck 1976). A total aerobic count was performed by the pour plate method using plate count agar (Speck 1976). The entire procedure was repeated twice.

The moisture content and water activity of a separate batch of mints prepared by an identical procedure was monitored over a 15 day period. Water activity was estimated by a Rotronic Hygroscope B water activity meter. (Rotronic AG, Zurich, Switzerland) using the method suggested by the manufacturer of the instrument. Pro- duct pH was determined by a pH meter standardized with a pH 4.0 buffer solution.

Results and Discussion

There was a slight decrease in moisture content during storage. This decrease was most obvious at room temperature and least obvious at - 10°C. There was no change in water activity, which remained near 0.86, regardless of the storage condition (Table 1). This level of water activity was considerably higher than that normally associated with traditional types of confectionary products (Hilker 1976).

The pH of this product was 4.1 at the time of preparation. This increased slightly to 4.4 over 21 days of storage at room temperature.

There were reductions in both the Salmonella and Staphylococcus populations dur- ing the first 24 h after preparation (Table 2). The reductions were greater than lo3 for Salmonella and ranged from lo2 to lo3 for Staphylococcus (Table 1).

Table 1. Moisture content and water activity (a,) of mints at time of preparation and after storage for four and 15 days at three different temperatures.

STORAG E 0 DA 1 A 5 A TORAGE TEMPERATURES % Mois tu re a,* B Mois tu re a,* % Mois tu re a,*

2 0 - 2 4 ' C 8 . 9 7 0 .87 8 . 4 5 0.8G 7 .54 0.86

5 - 7 OC 8 . 9 7 0 . 8 7 8 . 8 7 0 .86 8.30 0 . 8 6

-1OOC 8 .97 0 .87 8 . 8 5 0 . 8 7 8 . 7 2 0 .86 *aw

286 D. SCHMlDT and S. C. RIDLEY

Table 2. Microbial population of inoculated mints at time of preparation and after 24 h at room temperatures, two trials, A and B.

V I A B L E COUNTS VIABLE COUNTS ORGAN ISM IMMEDIATELY FOLLOWING AFTER FIRST 24 h

PREPARATION

TRIAL A TRIAL B TRIAL A TRIAL B

Salmone 11 a* > l o 6 > l o 6 < l o 3 <10

S t a u h y l o c o c c u s * * - . a u r e u s 2 . 6 x lo6 7 . 5 x 105 ~ 1 0 3 2 x 1 0 3

*Colony f o r m i n g u n i t s p e r gram o f p r o d u c t . * * E s t i m a t e d f rom s a m p l e d i l u t i o n where e x t i n c t i o n o c c u r r e d .

Table 3. Microbial population of inoculated mints after storage at 22°C. and -10°C for three weeks following preparation, two trials. A and B.

ORGAN ISM STORAGE TEMPERATURE 2 0 - 2 2 'C 5-7 O C -10 O C ---

Salmonel la* (10' (10' <lo5 < l o 3 40' , < l o 3

S taphylococcus 1 x 10' 4 x l o * 1 . 3 x 10' 5 .5 x 10' aureus**

T o t a l count** 3 . 4 x 10 ' 3.5 x 10 ' 3.1 x 10' 5.6 x 10' 1.1 x 1 0 ' 5 x l o '

*Es t imated from sample d i l u t i o n where e x t i n c t i o n o c c u r r e d . **Colony forming u n i t s p e r gram o f p r o d u c t .

Table 4. Sensory panel preference ranking of cream cheese mints stored at different temperatures for three weeks.

TREATMENT MEAN ADJUSTED RANKED SCORES

F r o z e n ( -10°C) 0.207a

F r e s h l y p r e p a r e d 0 . 2 0 0 a

R e f r i g e r a t e d (5-7'C) - 0.8 gab

Room T e m p e r a t u r e (20 -24 'C) -0.289b

abThose means s u b t e n d e d b y common l e t t e r s were not s i g n i f i c a n t l y d i f f e r e n t a t P<O.O1 as d e t e r m i n e d by Duncan ' s N e w M u l t i p l e Range T e s t ( 1 9 6 0 ) .

During storage for three weeks at room temperature, the populations of both Salmonella and Staphylococcus continued to decline (Table 3). During storage at 7 "C and at - 10 "C however, there was no further reduction of Salmonella. The

CHARACTERISTICS OF CREAM CHEESE MINTS 287

Table 5. temperatures for three weeks.

Mean sensory panel scores for flavor of cream cheese mints stored at different

TREATMENT MEAN FLAVOR SCORE

F r e s h l y p r e p a r e d 0.444a

Frozen (-10°C) 0.431a

R e f r i g e r a t e d (5-7OC) 0.028b

Room tempera tu re (20- 24'C) -0.34 7 c

abcThose means subtended by common l e t t e r s were no t s i g n i f i c a n t l y d i f f e r e n t a t PtO.05 a s de t e rmined by Duncan's N e w M u l t i p l e Range T e s t (1960) .

Table 6 . ferent temperatures for three weeks.

Mean sensory panel scores for textural moistness of cream cheese mints stored at dif-

TREATMENT MEAN TEXTURAL MOISTURE SCORE

Frozen (-10°C) 0 . 764a

F r e s h l y p r e p a r e d 0.333b

R e f r i g e r a t e d (5-7OC) 0.13gbC

Room tempera tu re (20-24'C) - 0 . 2 2 2 c

abcThose means sub tended by common l e t t e r s were no t s i g n i f i c a n t l y d i f f e r e n t a t P=O.O1 a s de t e rmined by Duncsn's New M u l t i p l e Range Test (1960) .

Staphylococcus aureus population continued to decline at 7"C, but not at - 10°C (Table 3).

Given the low pH, 4.1, and water activity, 0.86, one would not expect microbial growth to occur even at room temperature. The lower limit of water activity for growth of Staphylococcus aureus was reported to be 0.85 (Hilker 1976). The fact that the microorganisms retained their viability, especially at - 10°C, is significant, however. Outbreaks of illnesses caused by Staphylococcus aureus in confectionary products are apparently not very common (Hilker 1976), but Salmonella has been a relatively more frequent cause of illness (Hilker 1976, Just and Speck 1981).

The sensory panel tests showed a highly significant preference for mints that were freshly prepared or stored frozen for three weeks, compared to those stored at room temperature or at 5-7°C (Table 4). Likewise, the panel rated the flavor of fresh mints and those stored frozen as being better than the refrigerated or room temperature

288 D. SCHMIDT and S . C . RIDLEY

stored mints (Table 5). The degree of textural moistness was apparently greatest in the frozen product (Table 6).

It is noteworthy that none of the scores for sensory panel ratings of flavor and texture were very high. On the seven point scale that was used, the 0.444 mean score for flavor and the 0.764 for textural moistness both fall between one, like slight- ly, and zero, neither like nor dislike. Although the panel obviously had preferences and characterized the frozen and fresh products as superior, the differences were small and the scores suggest a less than enthusiastic reception for the product as a whole. This seems strange in light of the widespread acceptance of this and similar products at banquets and other festivities, and may be the result of employing a panel made up only of students.

Nevertheless, it appears from this experiment that a frozen commercial facsimile of this product, containing cream cheese has potential for success provided that nor- mal sanitary procedures for preparation are employed. Perhaps the flavor and tex- ture could be improved to increase overall acceptance.

REFERENCES

BANWART, G . J. 1979. Basic Food Microbiology. AVI Publishing Co., Westport, Conn .

FISHER, R. A. and YATES, F. 1957. Statistical Tables for Biological, Agricultural and Medical Research. 5th Ed. Hofner Publishing Co., New York.

HILKER, J. S. 1976. Confectionary Products. In Compendium of Methods for the Microbiofogicul Examination of Foods, (M. L. Speck, ed.) American Public Health Association, Washington D.C .

JUST, E. and STRAUSS, R. 1981. Schadliche mikroorganismen in sussworen. Zuker und Susswarenwirtschaft. 34 (9), 282-284, 286-287).

RICHARDSON, T. 1980. Nutritious Confectionary Foods. Manufacturing Confec- tioner. 60 (lo), 47-48, 40, 53, 54.

SPECK, M. L. (ed) 1976. Compendium of Methods for the Microbiological Evalua- tion of Foods. American Public Health Association, Washington, D.C.

STEEL, R. G. D. and TORRIE, J. H. 1960. Principles and Procedures OfStatistics. McGraw Hill, New York.