George M. Hall

Pilot scale lactic acid fermentation of shrimp wastes for chitin recovery

Abstract Lactic fermentation of shrimp waste on solid substrates was studied as a means of preservation for chitin recovery. Shrimp wastes were fermented in 100-g flasks with varying levels of inoculation with lactobacilli as well as different types and levels of carbohydrate. Sucrose was selected as the carbohydrate source in further experimental work due to its better acid production potential as compared to lactose and milk whey powder. Lactic acid fermentation was scaled-up from 2 to 30 kg in column reactors using geometric similarity as the scale-up criterion. The pH rapidly decreased to less than 5.0, allowing preservation of wastes for at least 3 months. During ensilation, deproteinisation and demineralisation were observed. Chitin obtained from the silage was treated with acid and alkali for mineral and protein removal.

Effect of initial glucose concentration and inoculation level of lactic acid bacteria in shrimp waste ensilation

Fermentation conditions and microorganisms were determined, based on acid production, glucose concentration as carbohydrate source. Inoculation levels to obtain a stable shrimp waste silage were also determined. Shrimp waste ensilation was an efficient method of preservation, allowing the recovery of chitin and another added-value products such as pigments, proteins and enzymes. From the various lactic acid bacteria tested, Lactobacillus pentosus and Lactobacillus sp. (B2) were the best lactic acid producers, although small quantities of acetic acid were detected in samples inoculated with Lactobacillus pentosus. Therefore B2 was chosen for the analysis of glucose consumption as well as for the determination of optimum inoculation levels. The best results were obtained at 10% (w/w wet basis) and 5% (v/w wet basis) respectively. Presence of starters and initial glucose concentration were critical factors in the fermentation of shrimp waste. High initial glucose and starter concentrations reduced the time and increased the amount of lactic acid produced. The fermentation pattern changed during ensilation from hetero to homofermentative. Shrimp waste ensilation prevented the growth of spoilage microorganisms keeping their microbial counts steady and pH values within the acid region.

Lactic acid fermentation of scampi waste in a rotating horizontal bioreactor for chitin recovery

Treatment of minced scampi (Nephrops norvegicus) waste, supplemented with glucose, in a bioreactor by a culture of the lactic acid bacterium, Lactobacillus paracasei strain A3, is described. The bioreactor comprised a mesh-covered basket mounted horizontally and enclosed within a glass outer jacket. The minced waste was placed inside the basket and agitation was provided by the controlled rotation of the basket. Batch fermentation was conducted over a period of 5 days at a temperature of 30°C, during which a protein-rich liquor was produced as a result of proteolysis. The pH of this liquor attained a value of 5·0 after a period of approximately 48 h, and under these conditions rapid solubilisation of calcium from the shell components of the waste occurred. At the end of the fermentation, the solid fraction comprised 17·5% chitin (dry weight basis) with, respectively, 77·5 and 61·0% of protein and calcium present in the initial waste material having been solubilised. The by-product liquor may have potential as an animal feed supplement.

Surimi and fish mince products.

The vast growth of surimi-based products in the USA and Europe has engendered a belief that everyone in the food industry knows what ‘surimi’ is. However, like that other buzz word of the 80s, ‘biotechnology’, everyone knows what they mean by surimi because they all have their own definitions.

Saccharification of cassava flour starch in a hollow-fiber membrane reactor

The enzymatic saccharification of cassava flour starch with Aspergillus niger glucoamylase was studied in a hollow-fiber enzymatic membrane reactor (HF-EMR). The optimization of the process was also investigated. The substrate was previously gelatinized by extrusion that produced a substrate with a degree of gelatinization and physical properties suitable for the enzymatic process. Typically, continuous saccharification of cassava flour starch in the HF-EMR produced a highly pure product in permeate (i.e., 99.6% glucose) with a global starch to glucose conversion of 97.3%. Results from a factorial experimental design revealed that retention time, enzyme to substrate ratio, and substrate concentration were the variables that most affected the process for starch to glucose conversion and for solid accumulation rate. Empirical models that describe this process were experimentally determined and compared with a theoretical model based on a balance of materials and enzyme kinetics. They were shown to adequately predict the performance of the HF-EMR.

Changes in the levels of histamine during processing and storage of fish meal

Abstract Processing and storage trials were carried out under controlled laboratory conditions to investigate the effect of processing and storage conditions on histamine formation during fish meal production. It was found that most histamine concentrated in the press liquor (stickwater) meal after processing. Histamine levels were mainly decreased in mackerel samples but increased in cod samples after processing into fish meal. Histamine was detected in the fish meal samples of fish offal of both cod and mackerel. No bacterial growth was observed in the press-cake when fish was cooked and pressed during fish meal production. After drying of solids and the stickwater, bacterial growth was observed. This is an indication that fish meal is apparently microbiologically hygienic after cooking process, then recontamination occurs. That samples were packed in polyethylene bags seemed to show a slight increase in histamine levels up to fifth week but a significant decrease (P