Tenderness classification of beef: IV. Effect of USDA quality grade on the palatability of "tender" beef longissimus when cooked well done.
(9/814)
The objective of this experiment was to determine the impact of USDA quality grade on the palatability of "tender" longissimus when cooked well done. Warner-Bratzler shear force was determined on longissimus thoracis steaks aged 3 or 14 d postmortem (cooked to 70 degrees C) from carcasses of 692 steers and heifers. Steaks from 31 carcasses with Modest or Moderate marbling scores (Top Choice) and steaks from 31 carcasses with Slight00 to Slight40 marbling scores (Low Select) were selected for this experiment from carcasses identified as "tender" (shear force < 5.0 kg at 3 d postmortem). Longissimus thoracis steaks with 3 or 14 d of postmortem aging were cooked to 80 degrees C and evaluated by a trained sensory descriptive attribute panel. Top Choice steaks had higher (P < .05) juiciness (5.8 vs 5.3) and beef flavor intensity ratings (4.9 vs 4.6) than Low Select steaks. Aging of steaks for 14, rather than 3, d postmortem improved (P < .05) beef flavor intensity rating (4.8 vs 4.7) but not (P > .05) juiciness rating (5.6 vs 5.5). The interaction (P < .05) of quality grade and aging time for tenderness rating indicated that Top Choice steaks were more tender (P < .05) with 3 d of aging than steaks from Low Select carcasses (6.3 vs 5.8), but steaks from Top Choice and Low Select carcasses had similar (P > .05) tenderness ratings after 14 d of aging (7.0 and 6.8). Compared to palatability of steaks from Low Select carcasses, the palatability of steaks from Top Choice carcasses was less affected by elevated degree of doneness in "tender" longissimus thoracis, especially when steaks were aged for only 3 d. Although differences in sensory traits between Top Choice and Low Select steaks were small, the consumers who cook beef well done may benefit from implementation of tenderness classification in conjunction with USDA quality grade. (+info)
The fate of folate polyglutamates in meat during storage and processing.
(10/814)
The rate of hydrolysis of chicken liver folate polyglutamates, by endogenous liver conjugases, under various conditions of storage, heat, and tissue disruption, were investigated. The procedure used was to allow a radioactive tracer dose of the vitamin to equilibrate into the folate polyglutamyl pool. After various storage periods and treatments the polyglutamyl state of the folate present was examined by analytical techniques based on oxidative degradation of native folate polyglutamates to the corresponding p-aminobenzoylpolyglutamate followed by chromatographic separation on DEAE cellulose anion exchange resin. Identification of folate polyglutamates present was made by simultaneous elution of known p-aminobenzoylpolyglutamate markers. In an intact tissue sample only slight degradation was found after 48 hr at 4 C; complete degradation of folate polyglutamates taking 120 hr. Samples of homogenized tissue show complete degradation to folate monoglutamates and a small amount of diglutamate after 48 hr storage. Superimposed on the above is the consideration that if at any time prior to or during storage the liver is heated to greater than 100 C irreversible inactivation of the endogenous conjugases takes place and the folate polyglutamate pattern is stabilized. It was also demonstrated that during two different heating procedures no extra deconjugation occurred. (+info)
Conversion of glucosinolates to isothiocyanates in humans after ingestion of cooked watercress.
(11/814)
Isothiocyanates (ITCs), major constituents of cruciferous vegetables, can inhibit tumorigenesis in rodents by modulating the metabolism of carcinogens. ITCs that occur as glucosinolates are released by myrosinase-mediated hydrolysis when raw vegetables are chopped or chewed. However, because cruciferous vegetables are commonly consumed by humans after being cooked, it is important to examine whether dietary glucosinolates are converted to ITCs after cooked cruciferous vegetables in which myrosinase is deactivated have been consumed. This information is useful for evaluating the potential role of ITCs in cruciferous vegetables in the protection against human cancers. A urinary marker, based on a cyclocondensation product formed by the reaction of ITCs and their conjugates with 1,2-benzenedithiol, was used to quantify the uptake of dietary ITCs in humans. At breakfast and lunch, nine volunteers consumed a total of 350 g of cooked watercress in which the myrosinase activity was completely deactivated. On the basis of the analysis of ITCs in the cooked watercress upon adding exogenous myrosinase, the amount of glucosinolates ingested by each subject was estimated to be 475 micromol. The 24-h urine samples showed that the total urinary excretion of ITC conjugates in the subjects ranged from 5.6 to 34.8 micromol, corresponding to 1.2-7.3% of the total amount ingested. On the basis of our previous results that approximately 50% of dietary ITCs were excreted in the urine as conjugates, these values represent the minimal in vivo conversion of glucosinolates to ITCs. For purposes of comparison, we carried out a second experiment in which 150 g of uncooked watercress were consumed. The percentage of urinary ITC conjugates excreted in this study ranged from 17.2 to 77.7% of the total ingested ITCs. These results indicate that glucosinolates are converted to ITCs in humans after ingestion of cooked watercress, in which the myrosinase has been completely inactivated. The extent of conversion, however, is considerably less than that after ingesting uncooked vegetables. Furthermore, upon incubation of the cooked watercress juice with fresh human feces under anaerobic conditions, approximately 18% of glucosinolates was hydrolyzed to ITCs in 2 h. These results suggest that the microflora in the intestinal tract are a likely source for the hydrolysis of glucosinolates to ITCs in humans. (+info)
DNA and protein adduct formation in the colon and blood of humans after exposure to a dietary-relevant dose of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine.
(12/814)
Epidemiology studies have indicated that certain dietary components, including well-cooked meat, are risk determinants for colon cancer. Cooked meat can contain significant quantities of heterocyclic aromatic amines (HCAs), which have been established as carcinogens in laboratory animals. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is usually the most mass-abundant HCA, with concentrations up to 480 ppb. We used accelerator mass spectrometry to establish whether DNA and protein adducts can be detected in humans exposed to a quantity of PhIP comparable with levels of exposure that occur in the diet. Five human volunteers were administered a dietary-relevant dose of [14C]PhIP (70-84 microg) 48-72 h before surgery for removal of colon tumors. Blood samples were collected at various time points, and albumin, hemoglobin, and WBC DNA were extracted for analysis by accelerator mass spectrometry. Tissue samples were collected during surgery and used to assess either tissue available doses of [14C]PhIP or adduct levels. The results of this study show: (a) PhIP is activated to a form that will bind to albumin, hemoglobin, and WBC DNA in peripheral blood. WBC DNA adducts were unstable and declined substantially over 24 h; (b) PhIP is bioavailable to the colon, with levels in normal tissue in the range 42-122 pg PhIP/g tissue; and (c) PhIP binds to both protein and DNA in the colon. DNA adduct levels in the normal tissue were 35-135 adducts/10(12) nucleotides, which was significantly lower than tumor tissue. The results of this study demonstrate that PhIP is bioavailable to the human colon following defined dietary-relevant doses and forms DNA and protein adducts. (+info)
Biomass cooking fuels and prevalence of tuberculosis in India.
(13/814)
OBJECTIVES: To examine the relation between use of biomass cooking fuels (wood or dung) and prevalence of active tuberculosis in India. METHODS: The analysis is based on 260,162 persons age 20 and over in India's 1992-93 National Family Health Survey. Logistic regression is used to estimate the effects of biomass fuel use on prevalence of active tuberculosis, as reported by household heads, after controlling for a number of potentially confounding variables. RESULTS: Persons living in households that primarily use biomass for cooking fuel have substantially higher prevalence of active tuberculosis than persons living in households that use cleaner fuels (odds ratio [OR] = 3.56; 95% confidence interval [CI] = 2.82-4. 50). This effect is reduced somewhat when availability of a separate kitchen, house type, indoor crowding, age, gender, urban or rural residence, education, religion, caste or tribe, and geographic region are statistically controlled (OR = 2.58; 95% CI = 1.98-3.37). Fuel type also has a large effect when the analysis is done separately for men (OR = 2.46; 95% CI = 1.79-3.39) and women (OR = 2. 74; 95% CI = 1.86-4.05) and separately for urban areas (OR = 2.29; 95% CI = 1.61-3.23) and rural areas (OR = 2.65; 95% CI = 1.74-4.03). The analysis also indicates that, among persons age 20 years and over, 51% of the prevalence of active tuberculosis is attributable to cooking smoke. CONCLUSIONS: Results strongly suggest that use of biomass fuels for cooking substantially increases the risk of tuberculosis in India. (+info)
NAT2 slow acetylator genotype is associated with increased risk of lung cancer among non-smoking Chinese women in Singapore.
(14/814)
Among non-smokers, the factors resulting in lung carcinogenesis are poorly understood. We conducted a hospital-based case-control analysis of 294 Chinese women, of whom 217 were non-smokers, to evaluate the role of polymorphic N-acetyltransferase (NAT2) as a susceptibility factor for the disease. The proportion of slow acetylator genotypes among non-smoking cases (n = 92) and controls (n = 125) was 38.0 and 24.0%, respectively [odds ratio (OR) 2.0, 95% confidence interval (CI) 1.1-3.7]. No effect of NAT2 genotype was seen among smokers. Among non-smokers, the effect was marked for adenocarcinomas (OR 2.1, 95% CI 1.1-4.0). As NAT2 activity is known to modify risk of arylamine-induced carcinogenesis, our results suggest that exposure to arylamines in the environment may play a role in risk of lung cancer among non-smokers. (+info)
An increase in sporadic and outbreak-associated Salmonella enteritidis infections in Wisconsin: the role of eggs.
(15/814)
In Wisconsin, reported Salmonella enterica serotype enteritidis (SE) infections during 1997 more than doubled compared with the previous 9 years. A case-control study was conducted to determine risk factors for sporadic infections, and results of outbreak investigations were reviewed. Eating raw eggs (matched odds ratio [MOR]=14.5; 95% confidence interval [CI], 1.7-591.6), eating raw or undercooked eggs (MOR=5.8; 95% CI, 1.3-28.0), eating any eggs (MOR=4.2; 95% CI, 1.2-16.2), and dining at a restaurant (MOR=4.7; 95% CI, 1.4-18.4) were associated with infection in the case-control study. For 3 of the 8 outbreaks, a probable source was identified, in each instance, foods containing eggs. Human infections decreased after eggs were diverted from implicated flocks. This epidemic demonstrates the continuing need for quality assurance on egg farms and enhanced education of consumers and commercial food preparers regarding safe handling of eggs. (+info)
Well-done, grilled red meat increases the risk of colorectal adenomas.
(16/814)
Red meat or meat-cooking methods such as frying and doneness level have been associated with an increased risk of colorectal and other cancers. It is unclear whether it is red meat intake or the way it is cooked that is involved in the etiology of colorectal cancer. To address this issue, we developed an extensive food frequency questionnaire module that collects information on meat-cooking techniques as well as the level of doneness for individual meat items and used it in a study of colorectal adenomas, known precursors of colorectal cancer. A case-control study of colorectal adenomas was conducted at the National Naval Medical Center (Bethesda, MD) between April 1994 and September 1996. All cases (n = 146) were diagnosed with colorectal adenomas at sigmoidoscopy or colonoscopy and histologically confirmed. Controls (n = 228) were screened with sigmoidoscopy and found not to have colorectal adenomas. The subjects completed a food frequency questionnaire and answered detailed questions on meat-cooking practices. We used frequency and portion size to estimate grams of meat consumed per day for total meat as well as for meat subgroups defined by cooking methods and doneness levels. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using logistic regression, adjusted for age, gender, total caloric intake, reason for screening (routine or other), and several established risk factors for colorectal adenomas or cancer, including the use of nonsteroidal anti-inflammatory drugs, physical activity, and pack-years of cigarette smoking. There was an increased risk of 11% per 10 g/day (or 2.5 oz/week) of reported red meat consumption (OR, 1.11; CI, 1.03-1.19). The increased risk was mainly associated with well-done/very well-done red meat, with an excess risk of 29% per 10 g/day (OR, 1.29; CI, 1.08-1.54) versus an excess of 10% per 10 g/day (OR, 1.10; CI, 0.96-1.26) for consumption of rare/medium red meat. High-temperature cooking methods were also associated with increased risk; 26% per 10 g/day (OR, 1.26; CI, 1.06-1.50) of grilled red meat and 15% per 10 g/day (OR, 1.15; CI, 0.97-1.36) of pan-fried red meat consumption. There was an increased risk of colorectal adenomas associated with higher intake of red meat, most of which was due to the subgroup of red meat that was cooked until well done/very well done and/or by high-temperature cooking techniques, such as grilling. These results are consistent with the hypothesis that carcinogenic compounds formed by high-temperature cooking techniques, such as heterocyclic amines and polycyclic aromatic hydrocarbons, may contribute to the risk of developing colorectal tumors. (+info)