SENSORY PROPERTIES AND CONSUMER PERCEPTION OF 'HOME-MADE'AND COMMERCIAL DAIRY ICE CREAM

Sensory properties and consumer perception of 2 'home-made'and 4 commercial dairy ice creams were examined. Conventional profiling by a trained panel found that most samples differed significantly in all attributes, but distinction of 'home-made'from commercial products was limited to few attributes. Principal component analysis separated the 'home-made'products from the commercial ones mainly on the basis of differences in appearance, aroma, creamy flavors and textural attributes. A consumer group (n=105) recorded preconception of 'home-made'ice cream acceptance, then received the product samples, in unlabeled condition, for assessment of degree of liking (DOL) and for identification as 'home-made'or commercial. Internal preference mapping of the DOL ratings showed that consumers were more closely grouped around samples which had higher intensities of certain attributes. Higher 'denseness', 'vanilla'aroma and 'buttery'flavor, were associated with more liking for commercial products. The 'home-made'high fat sample, although liked, tended to be grouped with commercial products. More marked textural attributes of 'ice crystals'and 'breakage'aided identification of the low-fat 'home-made'formulation, which was less liked overall. Overall, differences between the 'home-made'and commercial samples were small but consumer perception of the term 'home-made'was viewed favorably for dairy ice cream.     

Changes in Cell Number and Cell Division Activity during Endosperm Development in Allohexaploid Wheat, Triticum aestivum L.

Nuclear or cell number, and the mitotic index, were recordedin endosperms of Triticum aestivum cv. Mardler to test if aparticular stage of endosperm development was critical in determiningthe final grain weight. The basal four florets of emasculatedspikelets (controls), and the third and fourth florets of spikeletswhere the two basal ovaries were removed (ovary-removed), weresampled at various times up to 360 h after hand-pollination.The coenocytic phase in endosperms ended about 84 h after pollinationregardless of both grain position and the treatment. The onsetof the cellular stage was characterized by the final large fluctuationsin the mitotic index reflecting the culmination of the synchronousnuclear division of the coenocytic stage. Thereafter, the mitoticindex fluctuated with smaller amplitudes and, by 216 h afterpollination, was < 1%. Neither floret position in the spikeletnor the treatment affected the pattern of alteration to themitotic index. However, ovary removal from first and secondflorets resulted in significantly heavier grains and higherendosperm cell number in the 3rd and 4th florets compared withthe controls. In all florets, mean endosperm cell number peakedat 280 h but decreased by 360 h after pollination. At this time,the mean cell numbers in endosperms of the 3rd and 4th floretsof ovary-removed spikelets were significantly higher than inthe corresponding endosperms in the controls. Thus, a key contributoryfactor in determining the final endosperm cell number may bethe number of cells which are lost during the late period ofthe cellular stage of endosperm development. Key words: Endosperm cell number, florets, grain weight, mitotic index, Triticum aestivum     

Effect of predatory fish presence on habitat use and diel movement of the stream amphipod, Gammarus minus

SUMMARY.

• 1 We examined how the presence of predatory fish affected macro—and microhabitat use and movement patterns of the amphipod, Gammarus minus Say, in a second order stream.
• 2 Among macrohabitats, amphipods were consistently more abundant in runs than in pools. Densities in pools were low regardless of fish presence, whereas low densities in runs were correlated with fish presence. Siltation and the lack of coarse substrate particles probably accounted for the scarcity of G. minus in pools. Among microhabitats, G. minus was more abundant in leaf litter and gravel than in silt/sand substrates. Fish presence did not affect microhabitat use in the field. Laboratory manipulations showed, however, that predation rates by green sunfish (Lepomis cyanellus Rafinesque) were significantly lower on amphipods in leaf litter than in other microhabitats.
• 3 Most movement by G. minus in runs occurred at night and was directed downstream. In the laboratory, amphipods significantly reduced swimming activity at night in response to water conditioned with green sunfish. In the field, however, amphipods were only slightly less active in runs at night when exposed to chemical cues of confined green sunfish. The distribution of amphipods in streams is influenced by the presence of fish, but chemical cues alone may not be important in triggering predator avoidance behaviours in nature.

     

Three Centuries of Protozoology: A Brief Tribute to its Founding Father,A. van Leeuwenhoek of Delft*

SYNOPSIS. It was exactly 300 years ago this month (August 1974) that the 17th century modest draper from Delft, Holland—Antony van Leeuwenhoek—discovered protozoa. Describing them, often with amazing accuracy considering the optical equipment he was using (simply a home-made “glorified”hand lens), in letters to the Royal Society of London, he established himself, certainly, as the founding father of protozoology. It is particularly appropriate for an assemblage of protozoologists to pay homage to this intrepid “philosopher in little things,”a man with an insatiable curiosity about his wee animalcules, on the tricentenary of his discovery of them, since it was an event of such long-lasting significance.     

Root Density and Water Potential Gradients near the Plant Root

The models of Gardner (1960) and Cowan (1965) for water transferto the plant root are used to estimate the differences in waterpotential between the root and the bulk soil for a wide rangeof root densities and water extraction rates at a series ofmatric potentials for a Yolo light clay. For root densities and extraction rates reported both in theliterature and in this paper there is good evidence to suggestthat the large potential gradients originally predicted by Gardnerand Cowan are restricted to situations involving very low rootdensities and high extraction rates in relatively dry soil.