Elsevier

LWT

Volume 122, March 2020, 108989
LWT

Microbial diversity during processing of Thai traditional fermented shrimp paste, determined by next generation sequencing

https://doi.org/10.1016/j.lwt.2019.108989Get rights and content

Highlights

  • Microbial structure of in-process samples extremely changed from the raw material.

  • M. caseolyticus and J. psychrophilus were found as the first time in shrimp paste.

  • Lentibacillus spp. was solely the most abundant bacteria in fermented sample.

  • Fifteen bacteria producing aminopeptidase may relate to good flavor of shrimp paste.

Abstract

Shrimp paste, one of the traditional Thai fermented food ingredients, is a mixture of small shrimp and salt fermented for 1–2 months which gives a unique and rich flavor to Thai dishes. Dynamics of microbial diversity during processing and its contribution to the flavor of shrimp paste was investigated by next generation sequencing. Bacteria containing aminopeptidase genes were analyzed to present the possibility relating to taste-enhancing di- and tripeptide generation. Furthermore, this study showed the difference of microbial community structure in shrimp pastes collected from various regions in Thailand. The microbial diversity structure dramatically changed from the raw materials since the first step of processing. Salimicrobium spp. (53.6%) and Salinicoccus spp. (44.0%) were the major population; however, they were decreasing during processing. Alkalibacterium, Macrococcus caseolyticus, Jeotgalicoccus psychophillus, and Staphylococcus spp. became visible. M. caseolyticus and J. psychrophilus were detected as the first time in shrimp paste products. Then in one-month fermented sample, Lentibacillus spp. was 3.3%. Although, as per our experimentation (water activity, salt and pH), we could not observe any significant difference among different products. In two-month fermented sample, Lentibacillus spp. was solely the most abundant microorganism. From aminopeptidase genes analysis, the abundance of Salinococcus spp. during preparation and Lentibacillus spp. during fermentation may relate to good flavor quality of shrimp paste.

Introduction

Shrimp paste, known as ‘Ka-pi’ in Thailand is one of the traditional fermented food ingredients used in Chinese and Southeast Asian cuisines, especially in Thailand for more than 100 years. It gives a unique and rich flavor to many traditional Thai dishes. Shrimp paste is produced from small planktonic shrimps (Acetes spp.) fermented with salt for 1–2 months. The fermentation process involves proteolysis from proteolytic enzymes from fish, and bacteria, which consequently releases amino acids and peptides, that contributes sensory characteristics of the fermented product (Pongsetkul, Benjakul, Vongkamjan, Sumpavapol, & Osako, 2017). It is well established that many amino acids and small peptides act as taste enhancers giving umami, sweet, salty taste, and/or kokumi in foods (Toldrá, Hui, Astiasaran, & Sebranek, 2014; Zhao, Schieber, & Gänzle, 2016). Therefore, investigating the microbial diversity in shrimp paste during processing is important for understanding the microorganisms involving in the product fermentation to obtain a better flavor quality of shrimp paste.

From the previous studies, Tetragenococcus halophillus, Tetragenococcus muriaticus, Tetragenococcus sp., Virgibacillus sp., Lentibacillus sp., and Salinicoccus sp. were found in shrimp paste (Kobayashi et al., 2003; Pakdeeto et al., 2007). However, these studies reported the microorganisms isolated by using selective culture media such as MRS agar, JCM media, which did not represent the whole microorganisms in the food of interest. To explore microbial species diversity, next generation sequencing (NGS) technique has been used as a powerful tool to study microbial community in fermented foods such as Korean chili paste (Nam, Park, & Lim, 2012), sourdough (Ercolini et al., 2013), kimchi (Jeong, Jung, Lee, Jin, & Jeon, 2013). Deep sequencing and the capacity to sequence multiple samples make metagenomic sequencing technology is an important technique in analysis of food microbiota (Ercolini et al., 2013; Jeong et al., 2013; Nam et al., 2012; Ohshima et al., 2019). Although, many studies on the applications of NGS approach in many fermented foods were widely investigated. To date, the information on Thai fermented shrimp paste has not been reported. The attempt to study on microorganisms contributed to flavor quality of shrimp paste was investigated by Qi, Dai, Wang, Sun, and Zheng (2018). The study observed the difference in microbiota profile during two-month shrimp paste fermentation. However, the information of microbiota profile in raw materials and in-processed products, and the relation of microbiota profile and its contribution on flavor have not been reported. Our study aimed to investigate dynamics of microbial diversity from raw materials, samples during preparation (before fermentation) and the probability of taste-enhancing di- or tripeptide production from those bacteria in shrimp paste. Furthermore, this study showed the difference of microbial community structure in shrimp pastes collected from various production regions in Thailand.

Section snippets

Sampling of shrimp paste samples

The shrimp paste samples included raw materials, in-process and finished product samples. The raw materials and in-process samples were collected from a production site located in Samutsakorn Province of Thailand. The raw materials were fresh planktonic shrimp and salt. The in-process samples were collected from each step of production process (Fig. 1). Fresh planktonic shrimp was mixed with salt in ratio 9:1 (%w/w) and rested at room temperature for two to 3 h (P1) and 12-h overnight (P2).

Physico-chemical analysis

At the beginning of the process (Table 1), Aw value of the mixture of shrimp and salt (P1) was 0.85 and gradually decrease during the production to 0.72 in P4, the sample before fermentation. Aw value did not change during 1-month (0.72 in P5) and 2-month fermentation (0.71 in P6) (https://link.springer.com/content/pdf/10.1007%2Fs13197-017-2804-4.pdf Pongsetkul et al., 2017). No trend of pH change during preparation and fermentation was observed. pH values of 1-month and 2-month fermented

Conclusion

The results of the present study are encouraging for the use of NGS to investigate the microbiota of shrimp paste since in raw materials, during preparation and fermentation and comparison of the commercial shrimp paste with different various regions in Thailand. The NGS data of shrimp paste showed Alkalibacterium spp., Macrococcus caseolyticus and Jeotgalicoccus psychrophilus which were not reported in cultured dependent method earlier and detected as the first time in fermented shrimp paste.

CRediT authorship contribution statement

Apiniharn Phewpan: Investigation, Writing - original draft, Data curation, Formal analysis, Software. Preecha Phuwaprisirisan: Resources, Methodology, Data curation. Hajime Takahashi: Methodology. Chihiro Ohshima: Methodology. Kannapon Lopetcharat: Software, Data curation. Punnida Techaruvichit: Writing - original draft. Suwimon Keeratipibul: Supervision, Conceptualization, Writing - review & editing.

Acknowledgements

Authors are grateful to Dr. Rabuesak Khumthong from Research and Development Center of Betagro Group for protease genes and alpha diversity analyses and Dr. Chirapiphat Phraephaisarn from Research and Development Center of Betagro Group for data sorting. This work was financially supported by Chulalongkorn University's Ratchadapisek Sompot Fund [CF5803230] and The Thailand Research Fund (Research and Researcher for Industry (RRi))[No. PHD60I0018].

References (30)

  • R. Daroonpunt et al.

    Chemical and physical properties of Thai traditional shrimp paste (Ka-pi)

    Journal of Applied Pharmaceutical Science

    (2016)
  • R.C. Edgar

    UPARSE: Highly accurate OTU sequences from microbial amplicon reads

    Nature Methods

    (2013)
  • D. Ercolini et al.

    Microbial ecology dynamics during rye and wheat sourdough preparation

    Applied and Environmental Microbiology

    (2013)
  • H. Hillmann et al.

    Formation of kokumi-enhancing γ-glutamyl dipeptides in Parmesan cheese by means of γ-glutamyltransferase activity and stable isotope double-labeling studies

    Journal of Agricultural and Food Chemistry

    (2016)
  • Cited by (0)

    View full text