ALBERT

Notes: — The carotenoid compounds present in fresh tea leaf were quantitatively extracted and separated by thin layer chromatography. Neoxanthin. Neoxanthin, violaxanthin, lutein, and β-carotene were identified and estimated by spectrophotometry. Quantitative studies showed that these carotenoid compounds decreased from about 0.053% (dry weight basis) in the fresh tea leaf to about 0.030% in the fermented (3 hr fermentation) leaf to about 0.026% in the fired black tea. This analytical study was followed by an investigation to determine how, and to what, these carotenoid compounds are altered during the black tea manufacturing process. The fate of β-carotene in tea fermentation was first studied in model systems. The model consisted of a crude soluble enzymes preparation extracted from fresh tea leaves, tea flavanols, and β-carotene. The model system was buffered at pH 5.4 and incubated for 30 min at 30°C. The volatile compounds formed in this system were studied by gas chromatographic analysis of headspace volatiles. It was found that β-ionone (identified by GLC retention time and mass spectrometry) was formed in this model tea fermentation system as a result of tea flavanol oxidation and drying of the reaction mixture after oxidation. Further, it was found that all three basic reaction mixture ingredients, i.e., active tea enzymes preparation, tea flavanol, and β-carotene were necessary for the production of β-ionone. While β-ionone was the major volatile product formed from β-carotene in these systems, experiments utilizing 15,15′.14C-β-carotene showed that several unidentified compounds also were formed. The formation of β-ionone from β-carotene during black tea manufacture was confirmed in separate experiments. Organoleptic and GLC headspace analyses showed that black teas made in the usual way except that β-carotene was added at the leaf maceration stage (stage which initiates fermentation) contained more β-ionone than control black teas. The results obtained with β-carotene have been generalized on paper for all of the carotenoid compounds known to be present in fresh tea leaf. The results of this work indicate that many of the important black tea aroma constituents are probably formed during the tea conversion process by oxidative degradation of the carotenoid compounds present in the system. The possible mechanism for these transformations is discussed.

Notes: U-14C-Linolenic was shown to be transformed in part to t-2-hexenal during the conversion of fresh tea leaf to black tea. In fact, t-2-hexenal was the only volatile compound which was formed during the conversion process. Further, the formation of t-2-hexenal was shown to be dependent on the enzymic conversion process since no t-2-hexenal was formed when the leaf enzymes were inactivated prior to adding the 14C–linolenic acid. Since linolenic acid is the major fatty acid present in fresh tea leaf and t-2-hexenal is a prominent component of black tea aroma, it must be concluded that this reaction helps to determine the character of black tea aroma.

Notes: SUMMARY– 392 samples of precooked frozen shrimps from 2 Chilean industries (A and B) were analyzed for total bacterial count, conforms and enterococci throughout a period of 8 months. 1-lb samples of breaded shrimp were received directly from the manufacturers after a freezing period of 10 days at —18δC. Total bacterial count ranged from 104 to 105 organisms perg. Conforms were absent in 65% of the samples from A, and in 40% of those from 8; 89.6% of the samples from A and 50.1% of those from B were bacteriologically acceptable considering a limit of not more than 50 coliforms per g. 98% of the frozen shrimp samples belonging to A contained enterococci, as did 66% of the samples from B. Smaller percentages (17% for A and 54% for B) of acceptable samples are obtained from both industries when 100 enterococci per g is considered as the limit. During the period of observation some sanitary measures were adopted and subsequent coliform counts improved. In plant A working conditions are better and the understanding of bacteriological grounds for the proper handling of food materials has led to the elaboration of a product of consistently better quality. Enterococci counts are in contradiction with coliform counts, since the low-level coliform samples are rejected on the basis of their enterococcal content. In plant B there is a better correlation between coliform and enterococcal counts. Though not investigated, this may be related to the precooking system employed: steaming in an enclosed conveyor in A versus immersion in boiling sea-water in B.

Notes: SUMMARY– 392 samples of precooked frozen shrimp from two Chilean manufacturers, A and B, were quantitatively examined for the presence of Staphylococcus aureus by direct plating on Difco mannitol salt agar (MSA, 10% NaCI). 140 samples (35.7%) were found to contain Staphylococci but only half of these had counts of over 100,82.4% remaining within the acceptable limit. Frozen shrimps are prone to contamination by Staphylococcus during processing, especially if hand-processed, but these results show that it is possible to obtain a good-quality product when stringent sanitary measures are observed. MSA was compared with Baird Parker's egg yolk medium (BPM) by plating simultaneously on it 141 samples from manufacturer B; BPM detected S. aureus in a smaller number of samples (7.8%), and gave rise to fewer colonies than MSA. BPM seemed to be inhibitory even to some Staphylococcus strains, i.e., it is unsuitable for use in these frozen foods. From 2 other manufacturers, C and D, 80 samples of frozen shrimp, together with 60 nasal swab samples from food handlers were plated to investigate some cultural characteristics of S. aureus. 57 strains of this organism were obtained, 41 belonging to shrimp samples and 16 to nasal carriers from both manufacturers. The strains were isolated and, when tested by anaerobic fermentation of mannitol, deep growth in cysteine agar, catalase and coagulase reactions, all gave positive tests. Phosphatase and DNase reactions were less constant. All the strains with 1 exception were sensitive to 8 antibiotics tested. Thus, the general properties ascribed to S. aureus species appear unaltered in frozen shrimps. 28 strains (49.1%) could be typified with the set of 21 international phages, most of them belonging to group III; only in manufacturer D strains coming from food and food handlers were phage type related. In manufacturer C most strains were untypable.