ACID‐TOLERANT BACTERIA IN CITRUS JUICES^a

Abstract

Available literature pertaining to the types of bacteria indigenous to citrus juices is very limited. Faville, Hill, and Parish (1) reported that bacteria comprised the majority of organisms isolated from samples of frozen concentrated orange juice and that Leucomostoc was the predominant genus present, while reports on the occurrence of coliform organisms by Patrick ( 6 ) , Wolford and Berry (11,12), and Wolford (10) constitute the remaining publications on this subject.Although the relatively high citric acid content of citrus juices exerts a bacteriostatic effect on most species of bacteria, experience resulting from 5 years of commercial production of frozen concentrated citrus juices indicates that from the standpoint of spoilage of the product, bacteria are probably of significance equal to or greater than normally-occurring yeasts and molds. Hayes (3), for example, has isolated strains of Lactobacillus brevis and Lactobacillus ~l a~t~r u~ which he believes were the causative organisms in several instances where spoilage had occurred in the lowerBrix stages of multiple-stage evaporators during low-temperature vacuum concentration of orange juice, Teunisson and Hall (a), on the other hand, studied organisms isolated from the surfaces of processing equipment in citrus canneries and concluded that "bacteria are probably not a major factor in influencing the quality of orange juice. ' ' Conflicting reports such as these have prompted this study of acid-tolerant bacteria in citrus juices. EXPERIMENTAL PROCEDURESource of organisms. Most organisms included in this study have been isolated from experimental lots of orange juice, both single-strength and partially concentrated, which have shown evidence of microbial activity. During the course of 2 seasons many such experimental lots of juice have been packed and stored a t different temperatures ranging from -8'F. (-22.2"C.) to 40°F. ( 4 5°C . ) . Certain of these packs, particularly those stored a t the higher temperatures, have developed "swells. " 011 microscopic examination these swells have been demonstrated to be caused by bacterial rather than yeaat activity, as might be expected.The remainder of the organisms studied were isolated from oranges partially or completely rotted internally. Some of these fruit showed very little or no external evidence of decomposition. The Hamlin oranges shown in Figure l illdstrate a bacterial rot of this type. Although the rotted fruit (right) cannot be easily distinguished from a sound fruit (left) except for a bro3n spot located at the stylar end (bottom right), the interior portion of the fruit (upper right) has almost completely deteriorated. I n this particular fruit the decomposition was most pronounced in the central cylinder and extended throughout the vesicles t o the albedo.

Viability of Lactobacillus plantarum in Orange Juice under Low pH and Temperature Conditions

“…This spoilage is usually characterized by a "butter" off-flavor attributed to microbial diacetyl production (Faville and Hill, 1952;Hays and Riester, 1952).…”

“…DUE TO THE ACIDURIC NATURE of lactobacilli and leuconostocs, species of these genera are primarily responsible for bacterial spoilage of citrus juices. This spoilage is usually characterized by a "butter" off-flavor attributed to microbial diacetyl production (Faville and Hill, 1952;Hays and Riester, 1952).…”

Isolattion and Identification of Lactic Acid Bacteria from Samples of Citrus Molasses and Unpasteurized Orange Juice

“…Species which have been reported as isolated from citrus products include: Lactobacillus brevis, L. plantarum, L. thermophilus, Leuconostoc mesenteroides and Le. dtxtranicum (Yanai et al, 1986;Faville and Hill, 1952;Hays and Riester, 1952;Hays, 1951). Based on the microbial identifications from the 195Os, other researchers have conducted various studies on citrus products using either those species of organisms previously identified or other industrially derived strains which are usually identified only to the genus level (Patrick and Hill, 1959).…”

The Origin and Significance of Faecal Bacteria in Citrus Juices

“…Hays (1951) demonstrated the presence of Lactobacillus spp. in spoilage outbreaks and Faville & Hill (1952), who studied the growth of acid-tolerant bacteria isolated from fruit and from single strength and concentrated juice, showed the ability of species of Leucomstoc, Lactobacillus, Xanthomonas and Achromobacter to survive or grow at p H levels of 4.0 and below. Ingram (1949, 1950) has shown the importance of yeasts in the spoilage of concentrated orange juice and Recca & Mrak (1952) extended the study of yeasts from the Rhodotorula and Zygosaccharomyces isolated by Ingram to 92 cultures of imperfect and ascospore producing yeasts, of which Candida, Zygosaccharomyces, Hanseniospora, Pichia and Saccharomyw were the most important genera.…”