Assessment of Heat Damage to Protein Digestibility From Fish Meals by in Vitro Pepsin Solubilization at Different Temperatures

Over-heating during the drying of fish meal causes complexing of certain amino acids and affects the status of cysteinelcystine AbstractThe effect of heat treatment during fish meal processing on amino acid racemization was studied. The hydrolysis-induced racemization rate (R) and the D-isomer content in the sample before hydrolysis (I) were differentiated by means of deuterium labelling and gas chromatography-mass spectrometry (GC-MS) analysis in selected ion monitoring mode. A preliminary experiment on laboratory-made herring meals cooked at 125°C for different time intervals showed aspartic acid (Asp) as the only amino acid with significant racemization before hydrolysis. Aspartic acid racemization rate appeared to be a nearly linear function of the duration of thermal treatment (R' = 0.93; P < 0.01). Analyses were carried out on several samples of commercial fish meals from different origin. Low-temperature-dried fish meals had a D -A s~ content, expressed as I = 100 [D-isomer concentration before hydrolysis / (D-+ L-isomer concentration before hydrolysis)], at less than 1%, while the D-isomer content of hightemperature dried fish meals exceeded 2%. Differences between the two commercial categories were statistically significant ( P i 0.001). Further studies are required in order to evaluate the effects of D -A s~ in protein of fish feeds and the role of the raw material and processing parameters in inducing amino acid racemization in protein of fish meals. KEY WORDS: aspartic acid, D-amino acids in protein, fish meal quality, GC-MS, processing conditions. racemization rate.

Section: Samplesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Aspartic acid racemization in fish meal as induced by thermal treatment

Luzzana

Mentasti

Moretti

et al. 1996

“…Pepsin digestibility was lowest for the freeze-dried herring meal, even when the lipid was extracted. Although a high lipid content will interfere with pepsin digestibility (March & Hickling 1982), the reason for the lower digestibility of the lipid-extracted freeze-dried meal relative to the values obtained for the press cake meals is not clear. However, the findings could be related to the more extensive lipid oxidation in the freeze-dried product ( Table 6).…”

Section: Methodsmentioning

confidence: 92%

“…Pike et al (1990) also reported that pepsin digestibility values were increased for meals produced from spoiled raw material. However, these workers and others (March & Hickling 1982) also reported that pepsin digestibility decreases as a result of high-temperature heating of fresh raw material. The pepsin digestibility method has been criticized for lack of sensitivity when comparing good-quality and excellentquality fish meals (Hardy & Masumoto 1990).…”

Section: Methodsmentioning

confidence: 94%

Influence of spoilage and processing temperature on the quality of marine fish protein sources for salmonids

Clancy¹,

Beames²,

Higgs³

et al. 1995

Press cake meals were prepared from previously frozen herring immediately following thawing and after storage for 8 or 12 days at 2-5°C. Each of the raw sources of hemng was subjected to two processing temperatures, 75°C and 1OO"C, during meal preparation. Also, protein hydrolysates were prepared using ocean perch when fresh or after storage at 2-5°C for 4 or 8 days. Subsequently, each of the three hydrolysates was dried at 85°C or 93°C.In two separate experiments, each of the hemng press cake meals and dried perch protein hydrolysates was blended with a reference diet in a 30:70 ratio (test protein source: reference diet).All diets contained 5 g kg-' chromic oxide as an indigestible marker. The reference diet and all test diets were provided to satiation to chinook salmon in salt water and rainbow trout in fresh water, with digestibility of organic matter, protein and energy measured by difference. Digestibility of protein was also measured by the pH-stat and dilute pepsin solubility in vitro techniques.The results indicated that variation in processing temperature to a maximum of 100°C had little effect on digestibility of marine fish protein sources. By contrast, raw material storage for 8 days or more at 2-5°C prior to processing was found to reduce organic matter digestibility and sometimes nitrogen digestibility in salmonids. In vitro measures of digestibility were of little help in predicting the nutritive value of the test protein sources. Cadaverine level in herring press cake meal was shown to be a good indicator of spoilage in the raw material.

“…System utility was evaluated using differentially processed fish meals. This approach was employed not only due to the commercial importance of rapid determination of meal digestibility, but also because a potential impact of processing industrial fish for meal may be a reduction in protein nutritive quality (Bender 1972;March 1982;New & Csavas 1995). The sensitivity of the open system was compared against that of a closed design.…”

Section: Introductionmentioning

confidence: 99%

An evaluation of open and closed systems for in vitro protein digestion of fish meal

Bassompierre

Børresen

Sandfeld³

et al. 1997

The availability of a rapid, cost‐effective, accurate and reliable method of assessing fish meal protein digestibility would greatly enhance and standardize quality‐control procedures in both the fish meal and fish feed industries. However, while several in vitro digestibility tests have been developed, few have been adopted by industry due to their time‐consuming nature, problems surrounding reliability and/or inconsistencies in predictive ability. The present investigation was undertaken to evaluate the utility and predictive qualities of two in vitro digestion assays of distinct design. Methods examined included a novel open system, wherein on‐line removal of digestion products was attainable, and a closed system, which permitted analysis of products following completion of the digestion process. Results provided by the two systems were compared using four differentially processed fish meals. The open system supplied information based upon the detected quantity of products below 10 kDa. The closed system provided measurement of free amino groups. Both methods were in agreement with respect to assessing the presence of hydrolysed product. Both systems furnished complementary data with respect to the characterization of fish meal protein quality. The closed and open systems provided insight upon digestibility and digestion kinetic profiles respectively.