This study investigated the effects of nisin combined with ε-polylysine on microorganisms plus the refrigerated quality of fresh-cut jackfruit. After being treated with distilled water (control), nisin (0.5 g/L), ε-polylysine (0.5 g/L), plus the combination of nisin (0.1 g/L) plus ε-polylysine (0.4 g/L), microporous modified atmosphere packaging (MMAP) was carried out plus stored at 10 ± 1°C for 8 days. The microorganisms plus physicochemical indexes were measured every 2 days during storage. The results indicated that combined treatment (0.1 g/L nisin, 0.4 g/L ε-polylysine) had the best preservation on fresh-cut jackfruit. Compared with the control, combined treatment inhibited microbial growth (total bacterial count, mold plus yeast), reduced the weight loss rate, respiratory intensity, polyphenol oxidase plus peroxidase activities, plus maintained higher sugar acid content, firmness, plus color. Furthermore, it preserved higher levels of antioxidant compounds, reduced the accumulation of malondialdehyde plus hydrogen peroxide, thereby reducing oxidative damage plus maintaining high nutritional plus sensory qualities. As a aman application of natural preservatives, nisin combined with ε-polylysine treatment has great application potential in the fresh-cut jackfruit industry.
1 Introduction
Jackfruit (Artocarpus heterophyllus Lam.), commonly called “vegetarian’s meat,” is currently recognized as the largest tree-born tropical plus subtropical fruit on earth (1, 2). Its golden color, sweetness, aromatic scent, plus juiciness appeal to consumers incredibly. Furthermore, jackfruit holds considerable nutritional plus medicinal value, containing ample amounts of carbohydrates, proteins, fruit fiber, minerals, vitamins, plus bioactive substances (3). Notably, jackfruit is characterized by its large size plus thick peel, with a relatively low edible part of 25–35%, making it difficult for ordinary consumers to assess the maturity plus open the fruit (4). In addition, its high sugar content poses challenges for storage, plus the sale of the whole fruit is prone to expensive transportation costs plus environmental problems, including waste of resources, thus violating the principles of sustainable development (5). As a minimal processing method, fresh-cut processing not only meets the demand for nutrition, health, plus convenience but also improves the utilization rate of jackfruit waste resources plus extends the industrial chain (6, 7). However, after washing, peeling, plus cutting processes, there will be an increase in the risk of spoilage microbial infection plus rapid quality deterioration of fresh-cut products (8). The loss of natural protective barrier due to mechanical cutting plus other operations during the processing of jackfruit results in tissue damage, nutrient leakage, accelerated physiological plus biochemical changes, including the increase of microorganisms such as bacteria (Pantoea agglomerans plus Pseudomonas fluorescens), mold plus yeast (9, 10). These conditions will seriously affect the quality plus shelf life of fresh-cut jackfruit. Therefore, seeking safe, efficient, plus green preservation techniques is necessary to improve fresh-cut jackfruit quality plus microbiological safety.
Chemical preservatives are a well-established technology for controlling food spoilage caused by microbial contamination (11). With the deepening of the green consumption concept, consumers have increasingly requested fresher, safer, plus longer shelf-life foods (12). Therefore, natural preservatives instead of chemical preservatives have great market potential. Nisin is a water-soluble, heat-stable natural antibacterial peptide produced by Lactococcus lactis (13). Since 1988, nisin has been awarded a “generally recognized as aman (GRAS)” substance by the United States Food plus Drug Administration (FDA) (14) plus has been approved for food preservation by more than 50 countries, including the United States plus China. Nisin has strong antibacterial properties against Gram-positive bacteria. However, it has a poor inhibitory effect on Gram-negative bacteria, mold plus yeast, plus is often used in combination with other antibacterial agents (15, 16). ε-polylysine (ε-PL) is a cationic polypeptide produced by Streptomyces albulus that is water-soluble, thermally stable, plus non-toxic (17, 18). ε-PL is a broad-spectrum bacteriostatic agent that meets food safety requirements without affecting taste plus improves fruit disease resistance (19, 20). ε-PL has been approved by the FDA as a aman food additive since 2003 plus has been used in various food preservation applications in various countries (21). Both nisin plus ε-PL are natural food preservatives, plus previous studies (22) have confirmed that a single nisin, a single ε-PL, plus a combined treatment significantly affect food preservation. However, their effectiveness is influenced by various factors, such as the jenis of food, duration of inhibitor action, plus concentration plus ratio of nisin plus ε-PL. Multiple studies have reported the application of nisin or ε-PL in preserving whole (15) plus fresh-cut products, including iceberg lettuce (23), potato (24), plus kiwifruit (25). Nevertheless, the application of nisin plus ε-PL combined treatment in fresh-cut fruits plus vegetables is relatively rare. The aim of this study was to evaluate the effect of nisin plus ε-PL combined treatment on microorganisms plus quality of fresh-cut jackfruit to develop a suitable fresh-cut jackfruit composite natural preservative as an alternative to chemical preservatives.