Freeze Concentratton by Layer Crystallization

ABSTRACT

Layer crystallization in laminar falling films has been studied for freeze concentration applications. A binary mixture of water and sucrose has been tested in order to compare with literature results from suspension crystallizers. The concentration of sucrose in ice, which is a measure for loss of solute. were from 0.4 to 26.5% for bulk concenwlions of sucrose of 5 to 40%. respectively. The time averaged ice growth rates varied from 3. l0-7 l0 3-10-6 m/s. The results are related to expressions for maximum ice growth rate developed from the gradient criteria. Also an expression for maximum ice growth rate from irreversible thermodvnamics is oresented. Althoueh the exwrimental results show that one–step layercrystallization has amuch lower separation effect than suspension crystallizers with washcolumns, multistep layer crystallization could provide an economical favourable freeze concentration process. A multistep process that combines freeze concentration and reverse osmosis is proposed. A case study shows that it is possibleto reduce the investment costs to less than half of existing processes, for dewatering capacity of 700kg per hour. The energy consumption is also reduced.     

Minced Fish Production From Capelin (Mallotus villosus). A New Method for Gutting, Skinning and Removal of Fat from Small Fatty Fish Species

A new method for the production of fish mince from a small fatty fish is presented. The method involves (a) cutting the fish into short pieces, (b) washing out the depot fat, dark pigments and viscera under acid (pH 4) or neutral conditions, and (c) bone separation. The resulting mince has a white appearance and a low fat content (approximately 7% of dry wt). The water-holding capacity of the acid mince is low, whereas neutral minces have values corresponding to cod mince. The fish oil can easily be recovered. Characterization of the lipids in capelin mince is presented.     

VOLATILE FLAVOR COMPOUNDS IN 'KUNUN ZAKI'- A NIGERIAN MILLET-BASED BEVERAGE

Flavor volatile compounds of Kunun Zaki beverage were collected and concentrated on a Tenax GC and identified on a GC‐MS. Collected and separated compounds were evaluated for their aroma impression. Twenty‐eight volatile compounds were detected in the Kunun Zaki beverage. These were made up of pyrazines, ketones, alcohols, aldehydes, hydrocarbons and pyrroline. The aldehydes and pyrazines contributed a much higher percentage peak area to the beverage volatiles than ketones, hydrocarbons and alcohols. Kunun Zaki beverage exhibits a characteristic sweet, roasty potato‐like flavor.     

AROMA COMPOUNDS OF MALTED ACHA (DIGITARIA EXILIS, STAPF)

The flavor extract components of malted ‘acha’ (Digitaria exilis), which have not been studied prior to this report, were determined by gas chromatography with a mass selective detector. Volatile compounds were identified with a NBS 43 K.1 mass spectra library by Probability Based on Matching (PBM). A total of 14 peaks were detected and identified in the malted sample. The volatiles included, four aldehydes, one aromatic compound, an ester, a terpene, one aliphatic alcohol, five heterocyclic compounds of six membered rings. Quantitatively, heterocyclic compounds were the most abundant class of compounds identified. Six compounds, ethylacetate, 1-hydroxy-2-propanone, hexanal, pyrazine, 2, 5-dimethylpyrazine and 2, 3-dimethylpyrazine were identified as potential contributors to the flavor of malted acha. There was not a significant difference between the aroma quality of acha and crystal malt.     

Remote sensing and model simulation studies of the Norwegian coastal current during the algal bloom in May 1988

Abstract

The Chrysochromulina polylepis bloom in Skagerrak in May 1988 had severe consequences for the sea farming industry. Following the unexpected occurrence of the bloom combined remote-sensing and model studies of the mesoscale circulation of the Norwegian coastal current were performed in support of the daily forecasts of the advance of the algal front. A passive tracer included in the model simulated the drift path of the algae demonstrating the impact of meanders and eddies. Qualitatively the results of the simulation were in good agreement with the direct observations until the bloom culminated, suggesting dominance of the physical processes. In contrast, biological processes lead to the algal mortality during the retreat.     

Quality of Main-moins Prepared from Whole or Dehulled Cowpea (Vigna unguiculata) Cultivars

Mom-moins, steamed cowpea (Vigna unguiculata) products, made from Texas Cream and Chinese Red peas were evaluated and compared to those from California Blackeye peas (control). Sensory evaluation by 11 West African panelists showed that good quality moin-moins could be prepared from the investigated cowpea cultivars if dehulled. Only Texas Cream pea cultivar produced good quality moin-moin from the whole peas, thus making the strenuous dehulling process unnecessary. Moin-moins made from Texas Cream peas also had higher protein and ash contents. Agtron values were positively correlated (p < 0.01) to the sensory color scores.     

AROMATIC COMPOUNDS IN THREE VARIETIES OF TURNIP GREENS HARVESTED AT THREE MATURITY LEVELS*

Turnip greens (Brassica rapa) are commonly consumed in the southern U.S.A. Typically, they have a bitter taste, which increases with maturity, probably because of increased levels of glucosinolates. While glucosinolate degradation products have been isolated from various members of the Brassica family, the effect of variety and maturity on these products has not been determined. This study focused on the glucosinolate degradation products of three varieties of turnip greens: Purple Top, Seven Top and Tokyo Cross, harvested 45, 60 and 75 days after planting. Four volatile components (benzene acetonitrile, benzene propane nitrile, 1H‐indole‐3‐acetonitrile and benzene ethyl isothiocyanate) were isolated, identified and quantified. All increased significantly (P < 0.05) as the greens matured; however, onlybenzene propane nitrile and 1H‐indole‐3‐acetonitrile were significantly affected (P < 0.05) by variety.