71 Journal of Food Protection, Vol. 63, No. 1, 2000, Pages 71±77 Copyright Q, International Association for Food Protection Effect of L-Glucose and D-Tagatose on Bacterial Growth in Media and a Cooked Cured Ham Product DERRICK A. BAUTISTA,* RONALD B. PEGG, AND PHYLLIS J. SHAND Saskatchewan Food Product Innovation Program, Department of Applied Microbiology and Food Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 5A8 MS 99-96: Received 9 April 1999/Accepted 17 August 1999 ABSTRACT Downloaded from http://meridian.allenpress.com/jfp/article-pdf/63/1/71/1669933/0362-028x-63_1_71.pdf by guest on 25 September 2021 Cured meats such as ham can undergo premature spoilage on account of the proliferation of lactic acid bacteria. This spoilage is generally evident from a milkiness in the purge of vacuum-packaged sliced ham. Although cured, most hams are at more risk of spoilage than other types of processed meat products because they contain considerably higher concentrations of carbohydrates, ;2 to 7%, usually in the form of dextrose and corn syrup solids. Unfortunately, the meat industry is restricted with respect to the choice of preservatives and bactericidal agents. An alternative approach from these chemical compounds would be to use novel carbohydrate sources that are unrecognizable to spoilage bacteria. L-Glucose and D-tagatose are two such potential sugars, and in a series of tests in vitro, the ability of bacteria to utilize each as an energy source was compared to that of D-glucose. Results showed that both L-glucose and D-tagatose are not easily catabolized by a variety of lactic bacteria and not at all by pathogenic bacteria such as Escherichia coli O157:H7, Salmonella Typhimurium, Staphylococcus aureus, Bacillus cereus, and Yersinia enterocolitica. In a separate study, D-glucose, L-glucose, and D-tagatose were added to a chopped and formed ham formulation and the rate of bacterial growth was monitored. Analysis of data by a general linear model revealed that the growth rates of total aerobic and lactic acid bacteria were signi®cantly (P , 0.05) slower for the formulation containing D-tagatose than those containing L-orD-glucose. Levels of Enterobacteriaceae were initially low and these bacteria did not signi®cantly (P , 0.20) change in the presence of any of the sugars used in the meat formulations. Compared to the control sample containing D-glucose, the shelf life of the chopped and formed ham containing D-tagatose at 108C was extended by 7 to 10 days. These results indicate that D-tagatose could deter the growth of microorganisms and inhibit the rate of spoilage in a meat product containing carbohydrates. Meat and meat products can be extremely perishable. cle is quite low (i.e., 0.90% lactic acid, 0.17% glucose-6- As such, methods are employed throughout the industry to phosphate, 0.10% glycogen, 0.01% glucose, and traces of retard deteriorative changes and to extend the period of ribose from the degradation of ATP, nucleotides and nucle- their acceptability. These techniques constitute various osides (8)), carbohydrates may be added to further pro- forms of meat preservation. A number of ingredients com- cessed meat products to give characteristic ¯avor and re- monly added to meat products during processing impart duced water activity. Unfortunately, the carbohydrate sup- preservative effects but to varying degrees. For example, plement can allow microorganisms, such as lactic acid bac- salt provides a limited preservative action against micro- teria, to grow and cause spoilage problems (7). Although organisms by lowering water activity; nitrite bestows lactic acid bacteria are desirable in fermented meat prod- marked bacteriostatic properties and when added at reduced ucts, in nonfermented ones their development contributes levels, it functions synergistically with salt to give certain to undesirable qualities. Moreover, these organisms can cured meat products effective preservation; sugar added to grow under low oxygen conditions and are therefore a ma- fermented sausages indirectly serves as a preservative due jor concern in vacuum-packaged meat products. to the lactic acid formed by starter cultures that results in Incidences of spoilage can be prevented or at least min- lower pHs; and various constituents of wood smoke impart imized with the introduction of food-grade chemicals to bacteriostatic and bactericidal effects (3). retard the onset of microbial colonization. Many researchers Yet, the proliferation of bacteria results in the prema- have attempted to suppress bacterial spoilage in meat using ture spoilage of food and continues to cause economic loss- synthetic organic compounds as preservatives. In the es for the industry (14). For one company, the annual loss health-conscience 1990s, the perception of natural is a key in revenue from a cured meat product due to souring was issue among consumers, especially when it has to do with deemed to be in excess of $100,000 (1). Such problems lie their food supply. As such, the addition of synthetic pre- mostly with undesirable fermentation of cured meat prod- servatives and bactericidal agents to meat does not accom- ucts containing high carbohydrate levels (7). Although typ- modate this view. ical endogenous carbohydrate in postrigor mammalian mus- An approach to retard spoilage and thereby extend the * Author for correspondence. Tel: 306-966-7804; Fax: 306-966-8898; shelf life of meat products is the exploitation of hurdle tech- E-mail: [email protected]. nology. Using this stratagem, one manipulates the environ- 72 BAUTISTA ET AL. J. Food Prot., Vol. 63, No. 1 Both L-glucose and D-tagatose exhibited no toxic, carci- nogenic, or teratogenic effects in tests carried out under conditions speci®ed by the U.S. Food and Drug Adminis- tration (10). Currently, the generally-recognized-as-safe sta- tus of D-tagatose is being assessed by the Food and Drug Administration. The purpose of this investigation was to evaluate the potential of L-glucose and D-tagatose to reduce the prolif- eration of bacteria in food systems. The growth of a variety of bacteria was tested in vitro in systems containing these alternative sugars and in situ in a simulated chopped and formed ham product to determine if the product's shelf life could be extended. Downloaded from http://meridian.allenpress.com/jfp/article-pdf/63/1/71/1669933/0362-028x-63_1_71.pdf by guest on 25 September 2021 MATERIALS AND METHODS Preparation of bacteria for carbohydrate test. For each FIGURE 1. Fischer and Haworth projections of D-glucose, L-glu- bacterium listed in Table 1, a loopful (;10 ml) of frozen culture cose, and D-tagatose. was inoculated into a test tube containing 1.5 ml of either brain heart infusion broth (Difco Laboratories, Detroit, Mich.) or MRS broth (Difco) to enrich for gram-negative and gram-positive bac- ment of meat to prevent the onset of growth of spoilage teria, respectively. The culture was incubated at 358C overnight organisms. In the case of lactic acid bacteria, a fermentable (;8 to 12 h) prior to the carbohydrate test. carbohydrate source is required for energy (3). By remov- ing that source, the growth of these organisms can be sup- Carbohydrate test to determine utilization of various sug- pressed. For meat products containing high levels of sugar ars by bacteria. D-Glucose (control) was purchased from Difco Laboratories while L-glucose and D-tagatose were acquired from (;2 to 7%) as part of the formulation (e.g., ham), substi- MD Food Ingredients (Union, N.J.). All sugars were prepared as tution of the carbohydrate source to one that is not recog- a 5% (wt/wt) stock solution and ®lter sterilized. The utilization of nizable by bacteria represents a hurdle to their growth. these monosaccharides by a variety of bacteria was examined us- There are several new candidate sweeteners developed for ing a simple carbohydrate assay by bromocresol purple (i.e., 59,50- food applications with a signi®cant reduction in metaboliz- dibromo-o-cresolsulfonephthalein [bromocresol purple]; J. T. Bak- able energy. An example of such a sugar is L-glucose (Fig. er Chemical, Co., Phillipsburg, N.J.) as a pH indicator. This acid- 1 s 1 1 2 1). It is an enantiomer of the naturally occurring D-glucose, type indicator (HIn H2O H3O In ) can operate in pH has a sweetness ;0.6 times that of sucrose, and offers no ranges from 5.2 to 6.8. A change in color from purple to yellow available energy when metabolized by humans (11). A sec- indicates a reduction in pH and hence, carbohydrate utilization. Therefore, the term 1 was used to denote a strong positive re- ond and most promising alternative sugar is D-tagatose (Fig. 1 1). It is a full-bulk naturally occurring monosaccharide that action when the system appeared completely yellow and ( )to denote a weak positive reaction when only a slight yellowness can be derived from whey or lactose and has a sucroselike was observed. The (1) term implies that the bacterium in question taste (n.b., sweetness 0.92 times that of sucrose) with no could utilize the monosaccharide as an energy source but only to cooling effect, aftertaste, or potentiation of off ¯avors (9). a limited degree under the experimental conditions employed. Unlike D-glucose, D-tagatose is a ketohexose and a 4-epi- When the microorganisms could not utilize the test monosaccha- mer of D-fructose; in cyclic form, it exists as a pyranose, ride, then the system remained purple in color and a negative whereas D-fructose is predominately found as a furanose. reaction, 2, was recorded. TABLE 1. List of bacteria used to determine carbohydrate utilization Bacteria Collection type Bacteria Collection type Lactobacillus frigidus NCIBa 8518 B.