Rice Cakes as Halal Food

Halal food is defined in the Quran, the holy book of Islam, and essentially means food that is permissible according to Islamic law. Halal food laws strictly prohibit the use of haram (which literally means prohibited), meaning that foods containing haram animals and any form of alcohol should not be included in halal foods designed for Muslims [1,2]. Among haram, the term alcohol extends beyond ethanol (ethyl alcohol) to include any organic compound with a hydroxyl functional group (-OH) bound to a saturated carbon atom, such as methanol, propanol, butanol, pentanol, and hexanol [3]. However, ethanol is considered haram for Muslims because it causes intoxication. Ethanol is the most common volatile compound in food produced by the fermentation of sugars and is widely used as an important organic solvent for flavorings, colorants, and preservatives in processed foods [4]. While ethanol can serve as a chemical food preservative, finding natural alternatives for ethanol for use as food preservatives in halal foods is necessary to ensure the safety of halal foods [5]. Various natural and naturally derived products have been tested for controlling the growth of pathogenic bacteria [6], and citrus extracts and organic acids have been reported to have effective antimicrobial activities. Previous studies have reported the antibacterial activities of bitter orange (Citrus aurantium), also called Seville orange [7]. Bitter orange originated from India, and its oil, peel, flowers, and leaves are classified as Generally Recognized As Safe (GRAS) food additives in Korea [8]. A previous study on the antibacterial activity of C. aurantium flowers confirmed their efficacy against all tested gram-positive and gram-negative bacterial species [9]. Another study also reported the antimicrobial activities of citrus extracts against the biofilms of Enterococcus faecalis.

 

Antimicrobial activity against foodborne pathogens is well documented for organic acids, which are natural substances present in various fruits and fermented products [11]. Organic acids can suppress the growth of microorganisms by flowing through the cell membranes of the microorganisms and becoming ionized inside the membranes. The microbial cell must maintain the intracellular pH by releasing hydrogen ions, as the acidic pH inside the cell damages the extracellular membrane by modifying and damaging enzyme activity and protein and DNA structure [12]. The high pKa value of organic acids increases the chances of them being in their non-dissociated forms that are favored for crossing cell membranes [13]. Changes in the permeability of the cell membrane hinder substrate transport, while pH changes inside the cell suppress NADH oxidation, thereby affecting the electron transport system and leading to the death of the microorganism [14]. For this reason, the use of a mixture of organic acids with different pKa values could be more advantageous than a single organic acid alone for food preservation [13].

 

One traditional preserved food in Korea is rice cake, which is made of rice flour and consumed as a meal or snack [15]. Korean rice cakes are gaining popularity in Islamic countries, but the use of ethanol as a preservative renders them haram. The typical method for preparing rice cake involves steaming a rice flour and water mixture and adding sugar or salt according to preference [16]. The steaming step causes the starch component to undergo retrogradation [17,18], with storage temperature and time commonly affecting the rate of retrogradation, with a maximum value at 5 ◦C [19]. Consequently, food products made from cereal grains can become hazardous, particularly due to contamination by Salmonella spp., Staphylococcus aureus, and Bacillus cereus [20]. Bacillus cereus (gram-positive), in particular, has been identified worldwide in outbreaks associated with cooked rice [21]. In Korea, 19.3% of the rice cakes with filling and 19.3% of the rice cakes without filling were reported to be contaminated with S. aureus [22]. The high moisture content and high water activities (AW over 0.85) have led to several foodborne outbreaks related to rice cake. In 2010, an investigation of microbial contamination in over 30 rice cake items in Korean retail stores revealed total microorganism counts of 2.36–6.89 log CFU/g, coliform counts of 1.32–4.69 log CFU/g, and B. cereus counts of 1.38–2.48 log CFU/g [23].

 

For these reasons, efforts must be made to ensure the microbiological safety of rice cakes. The common industrial practice in Korea is to use ethanol as a microbial preservative by spraying or briefly soaking rice cake before packaging [1]. However, this use of ethanol limits the permissibility of these rice cakes for consumption by persons following halal food diets. Therefore, the objective of this study was to investigate the use of natural antimicrobial agents that could replace ethanol as a preservative in halal food. We evaluated quality changes in rice cake by microbial analysis (total plate count and mold and yeast counts) and color and texture tests at 0, 7, 21, and 28 days after treatment. Sensory quality was determined based on a sensory panel evaluation at 8 and 35 days.

 

Table 1 shows the antimicrobial effect of each treatment on the total plate counts (TPCs) and yeast counts from the rice cake. Regardless of the treatment, the populations of microorganisms increased over time. On Day 0, the rice cake treated with ethanol had the lowest total plate counts among the samples, indicating an immediate antimicrobial activity of ethanol. Notably, the MCO-treated rice cake had the lowest total plate counts at 28 days. GSE is well known to act as an effective natural antimicrobial agent. Compared to GSE, the MCO-treated rice cake reduced the TPCs by 3.05 log CFU/g (day 28). The ethanol-treated rice cake showed the lowest microbial count at day 0 among all samples, but the MCO-treated rice cake showed the least microbial growth after 28 days of storage, confirming MCO as an effective antimicrobial agent during storage. After 21 and 28 days of storage, the ethanol-treated and MCO-treated rice cake had significantly different TPC values compared with the distilled water-treated and GSE-treated rice cake

 

onclusions This study evaluated the efficacy of a newly developed mixture of citrus extracts and organic acids (MCO) to improve the physicochemical properties and microbial stability of rice cake. Our analysis of various characteristics, such as microbial analysis, hardness, color value, and consumer liking, revealed that MCO restricted and retarded microbial organism growth over a 28-day shelf life. In addition, the MCO left no alcoholic odor or taste, which is a main issue among manufactured rice cakes. MCO treatment also did not significantly affect the perceived sensory characteristics of rice cake; therefore, MCO preservatives may not negatively affect consumer acceptance of the treated products. Lastly, MCO samples met the halal regulations regarding ethanol content. Therefore, the MCO preservatives could be a useful alternative for use in the halal food industry. Further research is needed on other processed foods to generalize the efficacy of this non-ethanolic antimicrobial agent and its application to halal foods. The MCO preservative was investigated only using total plate counts and mold and yeast counts in the present study. Tests of the inhibitory activity Foods  against target toxigenic strains are still needed to verify the safety of using MCO as a rice cake preservative.